@@ericb0422 just joking. Thanks for watching my stuff. And technically my titles aren’t clickbait. I deliver on the promise. Legitbait would be a better description. True clickbait is deceiving and lying.
@@WoodcraftBySuman actually it was a good video with a full explanation of the difference between metal inserts and wood threads. To be honest it looks like wood threads will save both time money and reduce chance of failure
I think it's important to note that the style of insert used here is designed for softwood, and was used in hardwood. They do make another style of insert for hardwoods, I think it would be interesting to see how well those hold up
True, I would assume similar to screws, a hardwood insert would have finer/more threads while a softwood insert would have coarser/fewer threads. It appears the inserts he used were coarse thread and cherry is a hardwood.
Gotta say, this one is a tad bit too flawed as a test. For starters, threaded inserts are not there to be stronger than a traditional mechanical wood joints. They're there for reliability of disassembly over time, including against weather. Wood moves around it with it in place, so it comforms to the insert wether there is a bolt in it or not. It doesn't deform due to wood breathing humidity. So you can disassemble, store, transport, wood breaths, and the threads for the actual bolt are still unchanged. Wood threads without the bolt in it, specially in soft woods, are more prone to deforming when humidity changes And as you pointed, you use different inserts for different woods. Less dense woods move more and can't hold as many threads per inch (which matters a lot for the strength of the bolt), so you relly on fiber compression more, effectively make it locally more dense, strengthening the wood and reducing movement. Denser woods already cmpress less, move less, are already stronger, and already hold finer threads better, so you use inserts with more threads. So not much of a surprise the threads with higher tpi survived longer. Specially since it has not gone through cycles of humidity change with the fastener off, so none of that wood movement the inserts are fighting against was a factor.
Two quick comments: 1 -- At first blush, the results are surprising. Upon reflection, the poor showing of the metal threaded inserts seems to relate to the low thread count of the exterior threads. Fewer threads per inch means less thread surface in contact with the wood, which should mean less strength. Since they make threaded inserts with higher external thread counts (for use with hardwoods, such as cherry), I imagine that those inserts would have done a better job in these tests. 2 -- Often, inserts are used in end grain. Threads don't hold as well in end grain. In general, lower tpi and deeper threads tend to work better in end grain. Thus, the inserts that failed in these tests may have excelled if tested in end grain. Bottom line: Just as it's important to pick the right kind of screw for the job, it's important to pick the right type of insert.
Also using #2 tap instead of #3 tap would be better, since there would be less wiggle or no wiggle at all. Maybe the problem would be the fact that #2 taps are for hand use mainly and so they are also ground at the end, on the other hand #3 are mostly machining taps, that have no taper at the end.
You are spot on! The length, diameter and number of threads makes a big difference to the outcome of this testing. He should have made the Insert and the bolt the same length and it would have been a more accurate test. Here are the numbers. At 0.6 inch the 1/4"20 has 10 threads engaged, but the shorter insert only has 3 threads engaged. That is a difference in square inch thread engagement area of: - 1/4" Bolt = 0.318 - Threaded Insert = 0.2478 That's a difference of -0.0702 Square inch of area or 22% weaker for the insert. If You had used the same length of insert as the 1/4" bolt then there would have been 4 insert threads engaged in the wood. that would make the difference of: - 1/4" Bolt = 0.318 - Threaded Insert = 0.334 That would be a difference of +0.016 or 4.9% stronger for the insert. 1/4"20 Bolt Area for one thread: 0.0318 square inches X 10 threads = 0.318 Insert Bolt Area for one thread: 0.0826 square inches X 3 threads = 0.2478 Insert Bolt Area for one thread: 0.0826 square inches X 4 threads = 0.3304 If a blind hole is not required then always use pronged captive T-nuts for wood. The are made of carbon steel and are far superior in strength and durability.
Great observation, I didn't realize how few threads those inserts have. And had no idea they made hardwood inserts! Now if you use hardwood inserts compared to wood threads in Hardwood, they will both have the weakest link (the wood) improved. But as for stripping out (or pull test) the thread depth would also be a large factor and I notice inserts are fairly short, so 1 advantage of wood threads is that you can make them quite a bit deeper (limited only by tap length).
@WoodcraftBySuman First I'd like to thank you for the video and the experimental test. These results are as expected as a 1/4-20 bolt has 20 engaged teeth per inch (TPI). A 1/4-20 insert however has about 12 TPI. The inserts are NOT intended to give you higher torque capabilities. They are used when something needs to be disassembled and reassembled multiple times. If you would have removed the bare 1/4-20 bolts completely from their holes and rescrewed on your 100 screw in test, I think you'd of found them to be stripped within 10-20 or so times from slight cross threading each time. The inserts failed around 30 because when you bottom out the screw to the metal insert, you overtorque the 12tpi threads on the insert that's engaged with the wood. Do that enough on high speed drill, of course it'll strip the wooden threads. Thread qty engagement matters allot with screws. The higher TPI, the higher the chance of cross threading when reassembling, but also higher the initial and repeated torque it can handle. But again, ty for the experiment.
I'm not sure what I'm missing here, but 1/4-20 thread is 1/4-20 thread with the same TPI no matter what material or medium it's in. TPI remains the same regardless of the engaged length. Yes? No?
The threaded insert nuts have just four spiral threads…if they were an inch long there would be about twelve…hence 12 TPI for the nuts. FWIW the bolts can only engage their threads for the internal threaded section of each nut…which isn’t much, but it is metal in metal. A bolt screwed full depth into threaded wood has its entire 20 threads of its one inch length engaged. Now if you had one inch long threaded nuts with a full twelve spiral threads cut into the wood…that would be strong.
@@contessa.adella OK...I think. I wasn't aware of this. I'll make a point to inspect one of these inserts at my next chance to get a better understanding of that. Many thanks for the reply....I learn something new every day!
@@donaldp9259 insert nuts are called 1/4-20, because they accept a 1/4-20 screw (metal to metal interface). The 1/4-20 nuts outter threads that interface with the wood are a non standard size with a thread pitch of roughly 12 TPI. So the weak part in a insert like this, is it's interface to the wood itself. A 1/4-20 threaded nut insert with 12TPI stacked up against a identical length 1/4-20 bolt alone, would always lose in a maximum or cyclical torque test.
@@HotSteel-kl9tb Thanks for that input. I've used these inserts in the past, but I really didn't realize that. So, I've learned something new this week....a good thing.
Some may not consider the use of them to be woodworking, but for “composite” materials like MDF and other particle board, these inserts are very useful, for both repeated dis-&assembly or distributing force for e.g. spring loaded hinge mechanisms. Those materials would not hold threads for long, if at all, and the inserts sort of act like a (more specialized) bushing in concrete walls. And even then it is a good idea to install the inserts through the material and use them from the “wrong” side of panels where possible so they get pulled into the material by forces applied, rather than just out of the material; for example, on a the lid of a seat with integrated storage and that is covered in upholstering and has no need to be made of solid wood.
Have you tried stabilizing the threads in MDF with some liquid CA glue? I wonder how that compares. Also if you're running from the back side anyway I would think a bolt and washer would be superior to any insert. I suppose an exception would be in a case where you couldn't insert the bolt from the back for some reason, and absolutely had to thread in from the front side. Even so, on that rare case you're probably better off cutting a couple shallow depressions and using a flange nut, as you can get a lot more surface area on the face of the board.
I completely agree. If it's done right it will last a long time. I have seen so many times though, especially in cheap particle board furniture, where it wasn't done right. The best ones are like you said, where it is pulled into the material. Then it's almost like having a nut on the other end. Even if it does become loose you may be able to get it to work by holding it while you tighten everything down. Of course, that also depends on where it is. You may have to use some CA glue to hold it in place until you get it tightened down. Other times you would do better just making another hole or using a different fastener.
You thought you were making a case for threaded inserts, but really you just made a good case against using MDF in applications where frequent re-assembly is a factor...in fact, if something needed to be portable MDF or similar composites would not even be on my list of materials because while it is solid, it cannot take hits well, it's heavy, and causes high degrees of wear on your tools.
@@alphaforce6998 Well yeah, obviously MDF is the "cheap" alternative, which is why it's used in basically everything. Any woodworker would rather use anything else (except maybe big-box construction plywood) but the cost limits for a particular job might force otherwise.
I'm surprised that no one has pointed out that those flanged metal inserts you are testing are designed to have the bolt enter and be tightened from the _back_side_, and not from the "front". Just the same way that T-nuts are used. When a bolt is inserted and tightened from the back side, the insert is pulled tight into the wood, and secured by the flange. When installed and used in this way, repeated install and remove of the bolt puts far less stress on the interface between the insert and the wood. (I have seen this correct installation method described in manufacturer info, but unfortunately, I don't have a link to share.)
@walterwinnipeg Yer a friggin prince for pointing this out as clearly as you did, as are many other commentators who’ve educated far beyond the scope of author of this video. MANY THANKS!
That's not how it is with most cheap furniture..the threaded insert often comes out because it goes in on the same side as whatever is screwing into it.
The ones I use have no flange but looks exactly the same except for that so they are not directional and thruholes are not what a woodworker wants so this is a very coomon use whatsoever they where designed. Therefore this is an interesting video 🙂
The tapered tap is a STARTER tap, that is its intended purpose in the tooling world. The bottoming tap is for blind holes where you do not want a thru hole.
Would definitely like to see this in other woods like pine, mdf, plywood etc. You also have to consider the wood expanding and contracting with the wood tapped threads. Would definitely make a cool part 2 follow up video if you decided to do it.
Would be even worst since they are softer woods, I have use this once on a table, and I regret forever. Dont use this for stressing areas of your projects! One thing missing on the test and actually hard to test is the movement, the stress, from using the product, for instance a table is allways being pushed and pulled so in a matter of days this metal inserts are loose and as soon as you try to tigh them.. they will loose the engagement on the wood.. Btw I would use use epoxy glue if I want to stick metal and wood.
I’ve always used epoxy with threaded inserts. I think that the CA glue probably wicks up into the wood and doesn’t create much of a bond at all between the wood and metal. Additionally, the brittle nature of CA glue means that it has very little shearing strength.
NEVER drive a screw into a metal thread insert with a drill or impact driver. Always use a screwdriver or allen wrench depending on the screw head type. You’re only supposed to snug them up lightly, then do another half to 3/4 of a turn to tighten them properly. When used right, the inserts work great.
Yer a friggin prince for pointing this out as clearly as you did, as are many other commentators who’ve educated far beyond the scope of author of this video. MANY THANKS!
Conversely, I've (improperly) used inserts to repair a hardwood office chair after the wood completely failed around the original screws. I cut 1/4-20 threaded rod to make studs and then torqued "furniture nuts" to somewhere in excess of 30 ft-lb. In one place I passed the rod entirely through the chair, with an insert on each side, to clamp the arms with said nuts. I used 35mm inserts with coarse, interrupted, deep threads - softwood inserts. Chair's still rock-solid after years of further abuse, although it desperately needs to be reupholstered again and the pedestal needs similar repair.
I just finished building a full size arcade machine out of 3/4" MDF using inserts. I can't see how I would have done it without inserts and still kept it mobile. I think for MDF or softer materials inserts are really the only way to go as I bet threading the MDF would have crumbled easily. For wood though I might go without the inserts in the future. Interesting test results that I didn't expect.
I tried wood tap threads several years ago, just to see if it would work, It did , worked well and have been using routinely with great results. Thanks for your video, it was interesting.
These inserts are made for particleboard and work really well. I use them in jigs all the time and have been using them in jigs for years. I also do a lot of 3D printed parts and used to tap the holes. I now use these fittings all the time and I can tell you for a fact they work well. I will always drill and tap where possible myself as it is neater and simpler but a lot of the modern boards are terrible quality in the first place. Great video though and shows that the old woodworkers that used wooden threads knew a fair bit about the stuff they were working with.
It'd be interesting to see tests done on different wood hardness. I'm thinking inserts advantage is strengthening softer/cheaper wood. (Why you often see this in IKEA/particle board furniture). Wood inserts are like drywall anchors in my mind.
I bet it would be a similar trend, though maybe CA glue would be more helpful regarding durability of wood-tapped threads. Pine is pretty strong, and the logic of how tapped threads grab the end of the fibers is pretty similar almost regardless of wood species; I don't expect it would approach drywall-anchor type dynamics until we start considering like redwood, balsa, or paulownia.
I was literally going to comment the samething. Of course the wood will hold up better the harder it is. Inserts will hold up better on softer woods like pine
I think the outer threads on the inserts are just not coarse/deep enough. The inserts in the video look like they are meant for very hardwood. I think the wood used in this experiment is soft wood. It’s almost like using a bolt meant for metal in wood. As I mentioned earlier, using inserts is like using much bigger bolts. The threads need to be much coarser to compensate.
The inserts points is repeated disassembly over time. Wood moves. People move the furniture. And when you stick the screw back in, the metal thread catches it the same way every time. Wood thread or screws do not.
I was aware of this already but thanks anyway for making it so concise. I go a step further and make my own tap from a slightly undersized bolt from one of the exact ones I'll be using to achieve the best possible fit. This is how I'll attach a guitar body to it's neck. Retired machinist who has learned a few tricks along the way. You have a new subscriber now, thank you.
Having worked in testing labs with very expensive Instron equipment, I am very impressed with your setup. Having just finishing a Lagun Table for my RV, using metal threaded inserts, I am tempted to take them out, plug the holes with dowels and just wood tap them. Job well done!
really interesting tests. I think i see 3 main issues with the methodology that i'd love to see you test out. 1. the countersink on the metal threaded insert is below the surface, which means your first test was fairly unequal. IF you make the countersink only deep enough to make the insert flush, you would have less upwards force on the threads each time you run it down, making for a more equal comparison 2. you mentioned that you can use a smaller pilot hole for wood tapped threads than you can when threading in metal. If you used a slightly smaller pilot hole for the metal threaded inserts, the tighter fit would improve the depth of the bite made by the insert, strengthening the threads. 3. Your conclusion is that wood tapped threads are stronger than one might think, but the point of failure on all the metal inserts was still actually the wood tapped threads. This leads me to think the real difference is my 2nd point, the relative size of the pilot hole. Try repeating the test using a 23/64 pilot hole and a much smaller chamfer, for example.
I agree - oversinking them means tightening them will try to extract them. And in any case, overtightening them will cause cam out. On the other hand, if that's how he'd use them in real life, those are the results he should expect.
I’m also curious about the efficacy of wood tapped threads in end grain since the wood surrounding the threads would be less likely to fail over a large area, but perhaps more likely to fail nearest to the threads. As with any other wooden connection point, I think choosing your attachment-point grain can make a very large difference in the performance of the connection. Be nice to see this tested in a follow-up video.
This is a super cool video and a great psa, I've heard guys say you can't even ever unscrew a screw one time or it won't work... because i have a habit of starting a screw in and if i see it's not going to pull the material down i will back it out again so it had the chance to start into the other wood... like with plywood or when the screw doesn't start into the second piece and lifts it up. Threads were originally invented on wood and the evolution of making thread cutter tools starts with wood! This idea saves money. The wood tap is probably nice to use but you can use any tap, or even a bolt itself, if you cut lengthwise grooves and taper the end you can make taps for the bolts you have
The inserts failed in the endurance test because th bolt was hitting them, and twisting, as opposed to pulling them as would be the case in actual use.
Shit... You're absolutely right. You're a fart smeller... And the stripping test. I read a few dozen comments and a bunch of engineers talked about thread and science bs ... You absolutely nailed the reason. Nobody else caught this, not even me. How could he fix the test? Place wood between the insert and the washer and bolt? You're the damn genius ... Whatcha got?
I like this! My question though, on the threaded inserts, what happens when you step down to a 3/8" pilot hole? Its way more common and more people might just grab that over a specialized bit, giving the insert a much tighter connection.
Main benefit is that it looks nice and professional and you can also get 1/4 x 20 decorative threads that look nice if they're visible anywhere. Very interesting to see holding strength difference though, thanks for putting that together!
Great video and surprising results. I sure don't consider this click bait. Anyway, just to comment, I never use metal inserts to apply forces from the side they are installed in. If I use them, it's in areas I can drill through the back and use them like a nut. Sure, they could still spin if over torqued, but are less likely to pop out easily.
Will, nice work. For wood I use forming, also called roll taps, which compress the wood rather than cut it. Perhaps this strengthens the bolt/wood interface. I’ve used this several times and no problems so far.
I would love to see this test done on different materials - hardwoods, softwoods, MDF, etc, etc. The results here are counter intuitive, because one would think the larger interference diameter of the inserts would interact with more wood fiber. Imagine a 1/2 " insert, with a 1/2 " to 1/4" reducer holding those bolts. BTW, I never use super glue where there are any impact loads. I use epoxy, or regular old Titebond.
Not using superglue on impact loads AS AN ADHESIVE makes total sense. But in this case, the superglue is used to bond the wood threads together to make the wood matrix stiffer - not to bond the metal to the wood. And because the wood matrix significantly reinforces the cured superglue (similar to the way steel can reinforce concrete), the resulting wood-CA matrix is MUCH less brittle than cured CA would be on its own.
the inserts are wider diameter yes, but have fewer threads interacting with the wood. If you look at one of these inserts, the outer threads have fewer than 20 threads per inch.
There is an important test type that you have not included that is important in takedown furnature - Resistance to Cross threading during assembly When using wood threads the bolt is quite capable of being aligned off axis to some degree and simply cutting itself a new thread in even harder woods, where a metal thread-sert you would notice the misallignment much more readily due to the resistance of driving metal into metal This is a key factor as many places where thread-serts are used are functionally blind rethreaded where you cannot easily see if the thread is cleanly entering While 35 insert and removal cycles to fail might sound underwhelming, consider it in the context you gave of numer of times moving - 11 or 12 in the USA or 8 in the UK that means that you are talking more than 3x expected movements in a life time - easily sufficient to the task Finally you also don't test a thread style the is unfortunately often forgotten as an option Through holes design so that if the thread is pulled the Champfered collar is pulled INTO the wood - this is the use case where these inserts blow out the competition
If you're starting them by hand, like you should, you would definitely feel if you're started to cross thread in wood. I've actually tried this making tap handles. The metal inserts were a real pain in the butt and would always go in crooked. remembered I had a tap and dye set and tried it out. It was much easier and was plenty strong for a tap handle. I could also easily tell if I wasn't starting the thread right and just backed off without any problem.
I'll buy that wood-thread cross-threading idea. But also acknowledge that threaded inserts are a pain to install plumb. And if you get one started crooked you've just messed up the hole you drilled... in quite possibly the one spot where the hole needs to go.
@@wernerviehhauser94 The tearout test was pretty extreme, and I think odd to happen with normal use, but still repairable. The most likely problem would be the insert stripping out completely, also a pretty easy fix.
Nice work. Two more test suggestions: End grain application. Plenty of knock down furniture uses a butt joint. Somewhat oversize the wood thread hole and add CA and baking soda in layers and then retap to bolt size. I think this will be the strongest but only needed for the rare high stress joints or to repair stripped out inserts that came with the furniture.
The test might be a little unfair if you’re tapping the entire 3/4” thickness and using a 3/4” bolt and comparing that to a shorter threaded insert that is only engaging with half as much wood. Additionally, it would be interesting to see how easy it is to cross threads with multiple insertions. The main advantage of inserts is in preventing user error.
Yeah I just can't believe people are watching this video and thinking it was a good test.. I guess it really highlights the different intelligence levels between people in the world... He picked one arbitrary threaded insert, using arbitrary bolts. Even in his video the BOLTS FAILED! He really should of tried a variation of different threaded inserts instead because ultimately a wooded insert with a larger diameter is going to have more surface friction to hold it in place assuming the threads are proper lengths. Instead he's using a threaded insert nut (in the wrong direction) that has a much wider thread gap that is effectively lowering the overall surface area. And because he installed it in the wrong direction, it's both trying to further thread the wood while pulling it at the same time.. This results in just destroying the entire thread very rapidly... I'm not even an engineer and I immediately can see how terrible this 'study' is..
One concern for wood threads is durability/sensitivity to cross threading when removing and reasserting the bolt multiple times. This where I think metal inserts would be at an advantage. At least that has been my observation.
@@lexugax he didn't unscrew and screw them completely though. When leaving a little bit of the screw left in there, it ensures you won't cross thread. That's not how disassembly and reassembly works. The damage is done outside of this test parameters.
I guess one explanation why the metal inserts failed is because they're not actually cutting threads in the wood like the metal tap does. They compress the fibers thus giving a much less stronger fit. Also this is probably why they always fail the same way. What would be interesting would be to find out what size of threads are on the outer part of the insert, tap a hole to this size and thread an insert in it. I know it sounds silly but I guess coarser threads (vs regular threads) and a better contact with the wood would reinforce the joint. Depending if this stronger than threading directly into the wood, it would give a good compromise of strength and not having to find odd size screws.
Thanks for taking the time to do such a detailed experiment and video. Your content quality and editing is great, I think you're going to have one of the next big woodworking channels!
Those inserts were made for plastics and similar materials. The ones for wood have different outside threads, they are longer and different shapes. These inserts were designed for making jigs.
No. They are not made for plastics. We use a star system and they are not driven in. These are also not for metal, AT ALL. ergo they are ubiquitous and used primarily in wood.
For another series of tests, try using different metal inserts (the ones I like have knife-like wings that cut a *LOT* deeper.), epoxy, etc. for the holes AND different materials, like softwood, softwood with drilled & tapped hardwood dowels, MDF, etc. Cheers!
I've found that the ones you describe are worse than the threaded inserts in pine as the knife edges rip through the wood fibres when torquing the screws up. Wherever possible I try to insert the threaded insert "upside down" so that the axial force is trying to pull the flange through the wood.
@@johnwatson8192 I fully agree that the inserts should be put in from the bottom of the board as much as possible, for just the reasons you describe. An even stronger option is to carve out a space in the bottom for a wingnut and epoxy it in place. That isn't going *ANYWHERE.*
Thanks for going to all this work to find this out!! I was quite surprised and quite happy not to have to use the metal inserts in all future projects - there are viable choices!! Also I subscribed. I think your title was spot on.
Based on your tests, you definitely should use the thread inserts. They are strong enough, and if they fail they will not destroy your furniture like your tests clearly showed when using wood threads. That is why stronger is not always better.
@apple butter, based on the tests shown in the video, the wood thread is stronger and if it breaks, it will damage all the wood surrounding the hole which would require a major repair.
@@applebutter4036 the upwards pull yea, but you'd have to do something serious to put that much force on it, and homnestly, if that happens the table or whatever you made propably has more damage then just threads
The Pilot hole used for the insert makes a big different in its holding strenght. I also tested this in cherry. I torqued a furniture connector bolt into the threaded insert to failure. The metal threads on the insert failed before the wood or the wood insert interface failed.
The inserts are designed for MDF and participle board. I’m a bit surprised they didn’t do as well as the threaded hardwood, i’m not shocked that they didn’t.
Like good research, such a video just leads to additional questions. Good job. Even if your methods didn't answer every question, good job. For me, the essential thing this demonstrates is that the number of threads biting into the wood is so important. Those style of inserts have fewer threads contacting the wood. They fail sooner when abused slightly.
This was interesting. I would like like to see you repeat all these tests, but with a board in between the threaded board and the bolt head. Because normally you would not have the bolt head is not in direct contact with the threads.
What an interesting experiment. Honestly, have never tried to put those inserts in really harsh conditions but I've alsways considered them as something sturdy and reliable. Thanks a lot for putting this into test.
Great video Suman! I recently read an article in an old version of FWW where Michael Fortune described his process for making wood tapped threads with CA glue for many of his jigs. Your video reinforces why he did!
Suman! Great to see you back on the channel. Hope the family is doing well. This is a very well performed series of tests and presentation of your data. It's something I've been curious about, and now I'm convinced. If you're going to continue testing, I would be interested to see performance of different wood glue on different wood species and in different grain-to-grain applications. I think the initial performance might produce useful data, and then if you glue a duplicate set of test pieces to repeat the tests again in a year, then the expansion and contraction effects through 4 seasons on the glue hold may produce different results.
Thanks Aaron! Great idea! I should consider going long term seasonal type tests and think ahead. I definitely have one in the pipeline on waterpoof and one on "oily" wood and glue performance. Taking some notes from your comment for possible future use. Appreciate you coming back to the channel! Great to hear from you
Very interesting! I never would have guessed! Another test idea; where I have access to the back side of the wood, and in places where it cosmetically doesn't matter, I have used tee nuts. These are incredibly strong IMO and easy to use, and pretty cheap when bought in bulk. Example; I have a piece of 3/4" plywood hinged at the floor in the doorway of my outdoor building. I originally used wood screws in the hinges and they stripped almost immediately. The tee nuts i replaced them with have been in place at least 15 years and still holding strong.
As a cabinetmaker, I was not surprised with your results but it was certainly interesting to get actual figures on the results; thank you. As for the title, contrary to some opinions, I think it was appropriate to the demonstration; there IS a problem with metal insets, they are handy, cheap but essentially weak.
A very interesting result. 2 comments as I think through this problem. Having the threaded insert fail is probably easier to repair than having the wood fail. Though at almost double the straight pulling force that seems like a no brainer. I wonder if sheer testing would fair similarly. Secondly, i do think 2 part epoxy is a better fixative for threaded inserts than ca glue, but based on these failures i would be curious if the difference would be noticeable. I trust threaded wood a lot more now based on this testing so than you for that, it is a great result indeed.
That is really fascinating and useful! Very thought provoking. Thanks so much! The only downside from just tapping the wood is the pullout failure mode. If the unglued threaded insert pulls out, you can drill it out, glue in a dowel, reinsert the threaded insert and be good to go. Much harder to recover from a failure of the tapped bolt (and maybe the glued insert too). But all around a great video!
Thanksn I think they both will have the same issue in the event of replacements. Because the threaded inserts fail between the outer thread and the wood, you’d need to reconcile the size of the pilot hole (upsize insert or plug and re-drill). Similarly, if the wood tapped thread fails, you can always upsize the hole and tap a bigger thread or apply the same plug and re-tap method. Just need to be mindful with grain orientation.
@@WoodcraftBySuman Hi! It looks like for the unglued insert pullout failure, yes you need to drill it out a little bigger, then just glue in a wooden dowel, then redrill to the original pilot hole size and reinsert the insert. Really the same as a typical stripped screw repair. The hole left at failure is fairly clean with little to no surrounding damage. For the failure of the tapped holes the board blows apart. Far too much damage to just drill out and insert a dowel and redrill. At least that is how it looked to me.
As a cranky old guy I've got to say what I'm thinking. This video is such a load of... Great Content!!! Nice job and thanks for the in depth look. I wonder what strenght relationship small diameter-small threads is to large diameter-large threads.... The metal threaded inserts that failed are large/large. Maybe next video?
I agree with your results. Provided i have enough depth i alway cut threads into the hard woods. MDF also behaves similarly with hardwoods. The amount of torque a 2-3 cm deep screw in mdf is surprising.
Thanks Daniel. Unfortunately no. But if you DM me on Instagram, I can send you some video of cutting those taps. It really is as simple as drilling a hole and then driving the two through.
Great video. I recently used some similar 1/4"-20 threaded inserts, also in cherry, and was surprised by how easily it stripped out while just installing them. Some of the inserts recommend different sized holes for different woods. I wonder how it would compare if you repeated this with a smaller hole for the inserts. And how different glues compare. I like to use a small hole and ease the friction with wood glue.
Project Farm will be proud of you, lol. Good tests. One of the recommendations for further related test, try this with particle or mdf boards (like IKEA). Though I doubt you can even tap the board, just insert test maybe?
I know this is an old video but.. I cant help wondering if the inserts were actually manufactured metric hence the closest imperial threaded hole had too much run-out? Actually, all the wood inserts I've used have been self-tapping.
There was a similar test made for 3d printed plastic by i think CNC kitchen with the ourcome that just screwing into plasric is that much more durable than a special threaded insert. But experience says that the threaded insert in this use is simply much nicer because it makes assembly smooth and easy, and also it doesn't cross thread on repeat use, you can just screw in blindly rather than having to carefully find the thread every time. In wood i will continue using threaded inserts as well. Because the failure is really benign when it happens, i just epoxy the insert right back in and I'm good.
Oh Will. Clickbait title. Unsubscribed.
Even though yours is the top comment for some reason I'm watching to see if it's actually clickbait. Thanks for the warning though
This is a joke right? Witt is in the running for the king of clickbait titles! He has good videos though and I watch almost all of them.
@@ericb0422 just joking. Thanks for watching my stuff. And technically my titles aren’t clickbait. I deliver on the promise. Legitbait would be a better description. True clickbait is deceiving and lying.
I love how accurate this comment is 🤣
@@WoodcraftBySuman actually it was a good video with a full explanation of the difference between metal inserts and wood threads. To be honest it looks like wood threads will save both time money and reduce chance of failure
I think it's important to note that the style of insert used here is designed for softwood, and was used in hardwood. They do make another style of insert for hardwoods, I think it would be interesting to see how well those hold up
What style is that?
True, I would assume similar to screws, a hardwood insert would have finer/more threads while a softwood insert would have coarser/fewer threads. It appears the inserts he used were coarse thread and cherry is a hardwood.
Gotta say, this one is a tad bit too flawed as a test. For starters, threaded inserts are not there to be stronger than a traditional mechanical wood joints. They're there for reliability of disassembly over time, including against weather. Wood moves around it with it in place, so it comforms to the insert wether there is a bolt in it or not. It doesn't deform due to wood breathing humidity. So you can disassemble, store, transport, wood breaths, and the threads for the actual bolt are still unchanged. Wood threads without the bolt in it, specially in soft woods, are more prone to deforming when humidity changes
And as you pointed, you use different inserts for different woods. Less dense woods move more and can't hold as many threads per inch (which matters a lot for the strength of the bolt), so you relly on fiber compression more, effectively make it locally more dense, strengthening the wood and reducing movement. Denser woods already cmpress less, move less, are already stronger, and already hold finer threads better, so you use inserts with more threads. So not much of a surprise the threads with higher tpi survived longer. Specially since it has not gone through cycles of humidity change with the fastener off, so none of that wood movement the inserts are fighting against was a factor.
Yeah, do this again in pine and see how they stack up. Most furniture isn't made from hardwood anymore.
Mine have held up for many years in both woods. DC of SB...
Two quick comments: 1 -- At first blush, the results are surprising. Upon reflection, the poor showing of the metal threaded inserts seems to relate to the low thread count of the exterior threads. Fewer threads per inch means less thread surface in contact with the wood, which should mean less strength. Since they make threaded inserts with higher external thread counts (for use with hardwoods, such as cherry), I imagine that those inserts would have done a better job in these tests.
2 -- Often, inserts are used in end grain. Threads don't hold as well in end grain. In general, lower tpi and deeper threads tend to work better in end grain. Thus, the inserts that failed in these tests may have excelled if tested in end grain.
Bottom line: Just as it's important to pick the right kind of screw for the job, it's important to pick the right type of insert.
Also using #2 tap instead of #3 tap would be better, since there would be less wiggle or no wiggle at all. Maybe the problem would be the fact that #2 taps are for hand use mainly and so they are also ground at the end, on the other hand #3 are mostly machining taps, that have no taper at the end.
You are spot on! The length, diameter and number of threads makes a big difference to the outcome of this testing. He should have made the Insert and the bolt the same length and it would have been a more accurate test. Here are the numbers.
At 0.6 inch the 1/4"20 has 10 threads engaged, but the shorter insert only has 3 threads engaged. That is a difference in square inch thread engagement area of:
- 1/4" Bolt = 0.318
- Threaded Insert = 0.2478
That's a difference of -0.0702 Square inch of area or 22% weaker for the insert.
If You had used the same length of insert as the 1/4" bolt then there would have been 4 insert threads engaged in the wood. that would make the difference of:
- 1/4" Bolt = 0.318
- Threaded Insert = 0.334
That would be a difference of +0.016 or 4.9% stronger for the insert.
1/4"20 Bolt Area for one thread: 0.0318 square inches X 10 threads = 0.318
Insert Bolt Area for one thread: 0.0826 square inches X 3 threads = 0.2478
Insert Bolt Area for one thread: 0.0826 square inches X 4 threads = 0.3304
If a blind hole is not required then always use pronged captive T-nuts for wood. The are made of carbon steel and are far superior in strength and durability.
Great observation, I didn't realize how few threads those inserts have. And had no idea they made hardwood inserts! Now if you use hardwood inserts compared to wood threads in Hardwood, they will both have the weakest link (the wood) improved. But as for stripping out (or pull test) the thread depth would also be a large factor and I notice inserts are fairly short, so 1 advantage of wood threads is that you can make them quite a bit deeper (limited only by tap length).
@WoodcraftBySuman First I'd like to thank you for the video and the experimental test. These results are as expected as a 1/4-20 bolt has 20 engaged teeth per inch (TPI). A 1/4-20 insert however has about 12 TPI. The inserts are NOT intended to give you higher torque capabilities. They are used when something needs to be disassembled and reassembled multiple times. If you would have removed the bare 1/4-20 bolts completely from their holes and rescrewed on your 100 screw in test, I think you'd of found them to be stripped within 10-20 or so times from slight cross threading each time. The inserts failed around 30 because when you bottom out the screw to the metal insert, you overtorque the 12tpi threads on the insert that's engaged with the wood. Do that enough on high speed drill, of course it'll strip the wooden threads. Thread qty engagement matters allot with screws. The higher TPI, the higher the chance of cross threading when reassembling, but also higher the initial and repeated torque it can handle. But again, ty for the experiment.
I'm not sure what I'm missing here, but 1/4-20 thread is 1/4-20 thread with the same TPI no matter what material or medium it's in. TPI remains the same regardless of the engaged length. Yes? No?
The threaded insert nuts have just four spiral threads…if they were an inch long there would be about twelve…hence 12 TPI for the nuts. FWIW the bolts can only engage their threads for the internal threaded section of each nut…which isn’t much, but it is metal in metal. A bolt screwed full depth into threaded wood has its entire 20 threads of its one inch length engaged.
Now if you had one inch long threaded nuts with a full twelve spiral threads cut into the wood…that would be strong.
@@contessa.adella OK...I think. I wasn't aware of this. I'll make a point to inspect one of these inserts at my next chance to get a better understanding of that. Many thanks for the reply....I learn something new every day!
@@donaldp9259 insert nuts are called 1/4-20, because they accept a 1/4-20 screw (metal to metal interface). The 1/4-20 nuts outter threads that interface with the wood are a non standard size with a thread pitch of roughly 12 TPI. So the weak part in a insert like this, is it's interface to the wood itself. A 1/4-20 threaded nut insert with 12TPI stacked up against a identical length 1/4-20 bolt alone, would always lose in a maximum or cyclical torque test.
@@HotSteel-kl9tb Thanks for that input. I've used these inserts in the past, but I really didn't realize that. So, I've learned something new this week....a good thing.
Some may not consider the use of them to be woodworking, but for “composite” materials like MDF and other particle board, these inserts are very useful, for both repeated dis-&assembly or distributing force for e.g. spring loaded hinge mechanisms. Those materials would not hold threads for long, if at all, and the inserts sort of act like a (more specialized) bushing in concrete walls.
And even then it is a good idea to install the inserts through the material and use them from the “wrong” side of panels where possible so they get pulled into the material by forces applied, rather than just out of the material; for example, on a the lid of a seat with integrated storage and that is covered in upholstering and has no need to be made of solid wood.
Have you tried stabilizing the threads in MDF with some liquid CA glue? I wonder how that compares. Also if you're running from the back side anyway I would think a bolt and washer would be superior to any insert. I suppose an exception would be in a case where you couldn't insert the bolt from the back for some reason, and absolutely had to thread in from the front side. Even so, on that rare case you're probably better off cutting a couple shallow depressions and using a flange nut, as you can get a lot more surface area on the face of the board.
I completely agree. If it's done right it will last a long time. I have seen so many times though, especially in cheap particle board furniture, where it wasn't done right. The best ones are like you said, where it is pulled into the material. Then it's almost like having a nut on the other end. Even if it does become loose you may be able to get it to work by holding it while you tighten everything down. Of course, that also depends on where it is. You may have to use some CA glue to hold it in place until you get it tightened down. Other times you would do better just making another hole or using a different fastener.
Excellent point about applying force in the “wrong” direction so the top flange would provide additional resistance.
You thought you were making a case for threaded inserts, but really you just made a good case against using MDF in applications where frequent re-assembly is a factor...in fact, if something needed to be portable MDF or similar composites would not even be on my list of materials because while it is solid, it cannot take hits well, it's heavy, and causes high degrees of wear on your tools.
@@alphaforce6998 Well yeah, obviously MDF is the "cheap" alternative, which is why it's used in basically everything.
Any woodworker would rather use anything else (except maybe big-box construction plywood) but the cost limits for a particular job might force otherwise.
I'm surprised that no one has pointed out that those flanged metal inserts you are testing are designed to have the bolt enter and be tightened from the _back_side_, and not from the "front". Just the same way that T-nuts are used. When a bolt is inserted and tightened from the back side, the insert is pulled tight into the wood, and secured by the flange. When installed and used in this way, repeated install and remove of the bolt puts far less stress on the interface between the insert and the wood. (I have seen this correct installation method described in manufacturer info, but unfortunately, I don't have a link to share.)
@walterwinnipeg Yer a friggin prince for pointing this out as clearly as you did, as are many other commentators who’ve educated far beyond the scope of author of this video. MANY THANKS!
That's not how it is with most cheap furniture..the threaded insert often comes out because it goes in on the same side as whatever is screwing into it.
T-nuts go on the far side but often the acorn nuts go on the bolt side because you're typically not using a through-hole.
@@brianwest2775 A threaded insert is not an acorn nut. An acorn nut is a domed cap nut.
The ones I use have no flange but looks exactly the same except for that so they are not directional and thruholes are not what a woodworker wants so this is a very coomon use whatsoever they where designed. Therefore this is an interesting video 🙂
The tapered tap is a STARTER tap, that is its intended purpose in the tooling world. The bottoming tap is for blind holes where you do not want a thru hole.
What's more surprising than the results is that Suman actually published a video!
😂😂 I love seeing all the other RUclips woodworking folks sass each other
Ouch lol
Haha ouch Scott 😂
🔥
Would definitely like to see this in other woods like pine, mdf, plywood etc. You also have to consider the wood expanding and contracting with the wood tapped threads.
Would definitely make a cool part 2 follow up video if you decided to do it.
Would be even worst since they are softer woods, I have use this once on a table, and I regret forever. Dont use this for stressing areas of your projects!
One thing missing on the test and actually hard to test is the movement, the stress, from using the product, for instance a table is allways being pushed and pulled so in a matter of days this metal inserts are loose and as soon as you try to tigh them.. they will loose the engagement on the wood..
Btw I would use use epoxy glue if I want to stick metal and wood.
The wood expansion would affect the inserts as well...I think wood screws exist because they work well in wood and can even stand up to reassembly.
Absolutely this. All the cheap wood or wood products would be very beneficial to know about. The three that you listed would be perfect.
I would also be interested to see tapped threads vs just driving the screw directly into a slightly undersized hole
@@MrNiceGuy442 I think the best bet would be epoxying in inserts tbh, the real value of inserts is for multiple re-assembly cycles.
I’ve always used epoxy with threaded inserts. I think that the CA glue probably wicks up into the wood and doesn’t create much of a bond at all between the wood and metal. Additionally, the brittle nature of CA glue means that it has very little shearing strength.
The longer the set time the more wicking... It is liquid for longer
@@Anyone700 maybe? Super glue is thinner and acetone the solvent used In the glue can permeate into materials quickly.
Drill for the insert, apply the CA glue, let it wick in and dry. Repeat as needed until the CA glue doesn’t just wick in. Then install the insert.
Yes. Epoxy is the ticket. CA-glue is just horrid mess.
Wood (sic) the gel CA work better in this situation so it doesn't wick into the wood?
As an engineer, just want to say I REALLY appreciate your methodicalness which improves the quality of your data
Also as an engineer, I want to highlight that your use of fictional words reinforces your status as an engineer.
@@hockeyerAs a Photographer, I just want to say, increase your vocabulary before patronising.
As a photographer who exclusively works for engineering firms this wordsmithing is absolutely on brand.
NEVER drive a screw into a metal thread insert with a drill or impact driver. Always use a screwdriver or allen wrench depending on the screw head type. You’re only supposed to snug them up lightly, then do another half to 3/4 of a turn to tighten them properly. When used right, the inserts work great.
Yer a friggin prince for pointing this out as clearly as you did, as are many other commentators who’ve educated far beyond the scope of author of this video. MANY THANKS!
Conversely, I've (improperly) used inserts to repair a hardwood office chair after the wood completely failed around the original screws.
I cut 1/4-20 threaded rod to make studs and then torqued "furniture nuts" to somewhere in excess of 30 ft-lb. In one place I passed the rod entirely through the chair, with an insert on each side, to clamp the arms with said nuts.
I used 35mm inserts with coarse, interrupted, deep threads - softwood inserts. Chair's still rock-solid after years of further abuse, although it desperately needs to be reupholstered again and the pedestal needs similar repair.
It's fine to use an electric driver as long as you use low torque settings (as he did) and are careful when you first get it started.
That doesn’t sound very idiot proof.
The lower clutch settings on a drill will torque the screws less than most people would with a hand tool
I'm not a woodworker but I have to do woodworker things, and you just solved a major problem for me. THANK YOU!!!
I just finished building a full size arcade machine out of 3/4" MDF using inserts. I can't see how I would have done it without inserts and still kept it mobile. I think for MDF or softer materials inserts are really the only way to go as I bet threading the MDF would have crumbled easily. For wood though I might go without the inserts in the future. Interesting test results that I didn't expect.
Crt or lcd?
I tried wood tap threads several years ago, just to see if it would work, It did , worked well and have been using routinely with great results. Thanks for your video, it was interesting.
These inserts are made for particleboard and work really well. I use them in jigs all the time and have been using them in jigs for years. I also do a lot of 3D printed parts and used to tap the holes. I now use these fittings all the time and I can tell you for a fact they work well. I will always drill and tap where possible myself as it is neater and simpler but a lot of the modern boards are terrible quality in the first place.
Great video though and shows that the old woodworkers that used wooden threads knew a fair bit about the stuff they were working with.
For your 3d printed parts a much better insert is the melt in type.
I didn't even know wood tapped threads were a thing. Thank you for the video.
It'd be interesting to see tests done on different wood hardness.
I'm thinking inserts advantage is strengthening softer/cheaper wood. (Why you often see this in IKEA/particle board furniture). Wood inserts are like drywall anchors in my mind.
I bet it would be a similar trend, though maybe CA glue would be more helpful regarding durability of wood-tapped threads. Pine is pretty strong, and the logic of how tapped threads grab the end of the fibers is pretty similar almost regardless of wood species; I don't expect it would approach drywall-anchor type dynamics until we start considering like redwood, balsa, or paulownia.
I was literally going to comment the samething. Of course the wood will hold up better the harder it is. Inserts will hold up better on softer woods like pine
I think the outer threads on the inserts are just not coarse/deep enough. The inserts in the video look like they are meant for very hardwood. I think the wood used in this experiment is soft wood. It’s almost like using a bolt meant for metal in wood. As I mentioned earlier, using inserts is like using much bigger bolts. The threads need to be much coarser to compensate.
The inserts points is repeated disassembly over time.
Wood moves. People move the furniture. And when you stick the screw back in, the metal thread catches it the same way every time. Wood thread or screws do not.
This is an area that I never thought about. I learned something new and extremely useful today. Thank you for sharing.
Too bad you likely left mis-informed because the test itself was setup for failure...
RUclipsrs misinforming people 1 video at a time.
I was aware of this already but thanks anyway for making it so concise. I go a step further and make my own tap from a slightly undersized bolt from one of the exact ones I'll be using to achieve the best possible fit. This is how I'll attach a guitar body to it's neck. Retired machinist who has learned a few tricks along the way. You have a new subscriber now, thank you.
Having worked in testing labs with very expensive Instron equipment, I am very impressed with your setup. Having just finishing a Lagun Table for my RV, using metal threaded inserts, I am tempted to take them out, plug the holes with dowels and just wood tap them.
Job well done!
really interesting tests. I think i see 3 main issues with the methodology that i'd love to see you test out.
1. the countersink on the metal threaded insert is below the surface, which means your first test was fairly unequal. IF you make the countersink only deep enough to make the insert flush, you would have less upwards force on the threads each time you run it down, making for a more equal comparison
2. you mentioned that you can use a smaller pilot hole for wood tapped threads than you can when threading in metal. If you used a slightly smaller pilot hole for the metal threaded inserts, the tighter fit would improve the depth of the bite made by the insert, strengthening the threads.
3. Your conclusion is that wood tapped threads are stronger than one might think, but the point of failure on all the metal inserts was still actually the wood tapped threads. This leads me to think the real difference is my 2nd point, the relative size of the pilot hole.
Try repeating the test using a 23/64 pilot hole and a much smaller chamfer, for example.
I agree - oversinking them means tightening them will try to extract them. And in any case, overtightening them will cause cam out. On the other hand, if that's how he'd use them in real life, those are the results he should expect.
I’m also curious about the efficacy of wood tapped threads in end grain since the wood surrounding the threads would be less likely to fail over a large area, but perhaps more likely to fail nearest to the threads.
As with any other wooden connection point, I think choosing your attachment-point grain can make a very large difference in the performance of the connection. Be nice to see this tested in a follow-up video.
It seems to boil down to the quality of the outer threads, of which the pilot hole size could be the dominant factor.
This is a super cool video and a great psa, I've heard guys say you can't even ever unscrew a screw one time or it won't work... because i have a habit of starting a screw in and if i see it's not going to pull the material down i will back it out again so it had the chance to start into the other wood... like with plywood or when the screw doesn't start into the second piece and lifts it up.
Threads were originally invented on wood and the evolution of making thread cutter tools starts with wood! This idea saves money.
The wood tap is probably nice to use but you can use any tap, or even a bolt itself, if you cut lengthwise grooves and taper the end you can make taps for the bolts you have
The inserts failed in the endurance test because th bolt was hitting them, and twisting, as opposed to pulling them as would be the case in actual use.
Shit... You're absolutely right. You're a fart smeller... And the stripping test. I read a few dozen comments and a bunch of engineers talked about thread and science bs ... You absolutely nailed the reason. Nobody else caught this, not even me. How could he fix the test? Place wood between the insert and the washer and bolt? You're the damn genius ... Whatcha got?
Use a bolt shorter then the insert.
just got my thread tapper bit thingy in. excited to try it!
I like this! My question though, on the threaded inserts, what happens when you step down to a 3/8" pilot hole? Its way more common and more people might just grab that over a specialized bit, giving the insert a much tighter connection.
yes, I would like to see this tested also
25/64 is about 10mm
Americans and their freedom units :D
This was an eye opener. Thanks for putting in the work so we don’t have to!
Main benefit is that it looks nice and professional and you can also get 1/4 x 20 decorative threads that look nice if they're visible anywhere. Very interesting to see holding strength difference though, thanks for putting that together!
Great video and surprising results. I sure don't consider this click bait. Anyway, just to comment, I never use metal inserts to apply forces from the side they are installed in. If I use them, it's in areas I can drill through the back and use them like a nut. Sure, they could still spin if over torqued, but are less likely to pop out easily.
Will, nice work.
For wood I use forming, also called roll taps, which compress the wood rather than cut it. Perhaps this strengthens the bolt/wood interface. I’ve used this several times and no problems so far.
You can make your own by tapering the thread of a bolt. Use a longer bolt to make aligning easier.
I would love to see this test done on different materials - hardwoods, softwoods, MDF, etc, etc. The results here are counter intuitive, because one would think the larger interference diameter of the inserts would interact with more wood fiber. Imagine a 1/2 " insert, with a 1/2 " to 1/4" reducer holding those bolts. BTW, I never use super glue where there are any impact loads. I use epoxy, or regular old Titebond.
Not using superglue on impact loads AS AN ADHESIVE makes total sense. But in this case, the superglue is used to bond the wood threads together to make the wood matrix stiffer - not to bond the metal to the wood. And because the wood matrix significantly reinforces the cured superglue (similar to the way steel can reinforce concrete), the resulting wood-CA matrix is MUCH less brittle than cured CA would be on its own.
the inserts are wider diameter yes, but have fewer threads interacting with the wood. If you look at one of these inserts, the outer threads have fewer than 20 threads per inch.
Thank you for doing the good work. This is the kind of valuable data that goes unseen in R and D. It’s tedious and so yet useful
There is an important test type that you have not included that is important in takedown furnature - Resistance to Cross threading during assembly
When using wood threads the bolt is quite capable of being aligned off axis to some degree and simply cutting itself a new thread in even harder woods, where a metal thread-sert you would notice the misallignment much more readily due to the resistance of driving metal into metal
This is a key factor as many places where thread-serts are used are functionally blind rethreaded where you cannot easily see if the thread is cleanly entering
While 35 insert and removal cycles to fail might sound underwhelming, consider it in the context you gave of numer of times moving - 11 or 12 in the USA or 8 in the UK
that means that you are talking more than 3x expected movements in a life time - easily sufficient to the task
Finally you also don't test a thread style the is unfortunately often forgotten as an option
Through holes design so that if the thread is pulled the Champfered collar is pulled INTO the wood - this is the use case where these inserts blow out the competition
If you're starting them by hand, like you should, you would definitely feel if you're started to cross thread in wood. I've actually tried this making tap handles. The metal inserts were a real pain in the butt and would always go in crooked. remembered I had a tap and dye set and tried it out. It was much easier and was plenty strong for a tap handle. I could also easily tell if I wasn't starting the thread right and just backed off without any problem.
I'll buy that wood-thread cross-threading idea. But also acknowledge that threaded inserts are a pain to install plumb. And if you get one started crooked you've just messed up the hole you drilled... in quite possibly the one spot where the hole needs to go.
This wasn’t what I initially suspected. I learned something. Subscribed.
You 100% just changed the way I will be building things going forward. Thanks for taking the time to make this!
You would rather go for severe and probably unrepairable damage rather than replace some cheap inserts?
@@wernerviehhauser94you would need to plug the holes in both cases so they are both reparable
@@Timopeo you did not really pay attention when watching the video, did you? Check the tearout.
@@wernerviehhauser94 The tearout test was pretty extreme, and I think odd to happen with normal use, but still repairable. The most likely problem would be the insert stripping out completely, also a pretty easy fix.
I am genuinely floored by this. Thanks for making this video, dude!
My pleasure!
Nice work. Two more test suggestions:
End grain application. Plenty of knock down furniture uses a butt joint.
Somewhat oversize the wood thread hole and add CA and baking soda in layers and then retap to bolt size. I think this will be the strongest but only needed for the rare high stress joints or to repair stripped out inserts that came with the furniture.
This was very informative and somewhat surprising. Thankyou. Next time I go to build something, I will not be wasting money on inserts
The test might be a little unfair if you’re tapping the entire 3/4” thickness and using a 3/4” bolt and comparing that to a shorter threaded insert that is only engaging with half as much wood.
Additionally, it would be interesting to see how easy it is to cross threads with multiple insertions. The main advantage of inserts is in preventing user error.
Yeah the wood threads looked much deeper than the insert.
Yeah I just can't believe people are watching this video and thinking it was a good test..
I guess it really highlights the different intelligence levels between people in the world...
He picked one arbitrary threaded insert, using arbitrary bolts. Even in his video the BOLTS FAILED! He really should of tried a variation of different threaded inserts instead because ultimately a wooded insert with a larger diameter is going to have more surface friction to hold it in place assuming the threads are proper lengths.
Instead he's using a threaded insert nut (in the wrong direction) that has a much wider thread gap that is effectively lowering the overall surface area. And because he installed it in the wrong direction, it's both trying to further thread the wood while pulling it at the same time.. This results in just destroying the entire thread very rapidly...
I'm not even an engineer and I immediately can see how terrible this 'study' is..
Wow this shattered my preconceptions about threaded inserts vs tapped threads. Great experiment!
One concern for wood threads is durability/sensitivity to cross threading when removing and reasserting the bolt multiple times. This where I think metal inserts would be at an advantage. At least that has been my observation.
He screwed and un-screwed the screws 100 times, and the metal ones didn't even make it to 40.
@@lexugax he didn't unscrew and screw them completely though. When leaving a little bit of the screw left in there, it ensures you won't cross thread. That's not how disassembly and reassembly works. The damage is done outside of this test parameters.
Excellent point, MANY THANKS! @@HotSteel-kl9tb
Thank you for doing this - completely unexpected results! I’m going to have to rethink my threaded inserts…
I guess one explanation why the metal inserts failed is because they're not actually cutting threads in the wood like the metal tap does. They compress the fibers thus giving a much less stronger fit. Also this is probably why they always fail the same way. What would be interesting would be to find out what size of threads are on the outer part of the insert, tap a hole to this size and thread an insert in it. I know it sounds silly but I guess coarser threads (vs regular threads) and a better contact with the wood would reinforce the joint. Depending if this stronger than threading directly into the wood, it would give a good compromise of strength and not having to find odd size screws.
Great info! Thanks for doing these tests!
Thanks Matt! Appreciate you watching.
Thanks for taking the time to do such a detailed experiment and video. Your content quality and editing is great, I think you're going to have one of the next big woodworking channels!
Once again. A wonderfully designed and executed test!!! Thank you for ALL you do!!!
Those inserts were made for plastics and similar materials. The ones for wood have different outside threads, they are longer and different shapes. These inserts were designed for making jigs.
No. They are not made for plastics. We use a star system and they are not driven in. These are also not for metal, AT ALL. ergo they are ubiquitous and used primarily in wood.
Congratulations, you have one of the best videos on YT that I have ever seen. Really nice job. Thank You.
For another series of tests, try using different metal inserts (the ones I like have knife-like wings that cut a *LOT* deeper.), epoxy, etc. for the holes AND different materials, like softwood, softwood with drilled & tapped hardwood dowels, MDF, etc.
Cheers!
I've found that the ones you describe are worse than the threaded inserts in pine as the knife edges rip through the wood fibres when torquing the screws up. Wherever possible I try to insert the threaded insert "upside down" so that the axial force is trying to pull the flange through the wood.
@@johnwatson8192 I fully agree that the inserts should be put in from the bottom of the board as much as possible, for just the reasons you describe. An even stronger option is to carve out a space in the bottom for a wingnut and epoxy it in place. That isn't going *ANYWHERE.*
SUper funny and educative video, never thought that only threaded wood could be stronger than the metal inserts!!
Thanks for going to all this work to find this out!! I was quite surprised and quite happy not to have to use the metal inserts in all future projects - there are viable choices!! Also I subscribed. I think your title was spot on.
Based on your tests, you definitely should use the thread inserts. They are strong enough, and if they fail they will not destroy your furniture like your tests clearly showed when using wood threads. That is why stronger is not always better.
Good point. It's an easy fix to plug a hole when a threaded insert fails. Worth putting some extra thought into it for sure.
@@applebutter4036 you can plugged the hole from a tapped hole also then. no?
@apple butter, based on the tests shown in the video, the wood thread is stronger and if it breaks, it will damage all the wood surrounding the hole which would require a major repair.
@@cyber2526 you can see in this video that there is a lot of damage when the wood threads failed. Be a tough fix compared to the threaded inserts
@@applebutter4036 the upwards pull yea, but you'd have to do something serious to put that much force on it, and homnestly, if that happens the table or whatever you made propably has more damage then just threads
The Pilot hole used for the insert makes a big different in its holding strenght. I also tested this in cherry. I torqued a furniture connector bolt into the threaded insert to failure. The metal threads on the insert failed before the wood or the wood insert interface failed.
The inserts are designed for MDF and participle board. I’m a bit surprised they didn’t do as well as the threaded hardwood, i’m not shocked that they didn’t.
Are the holes of same length in the test?
Like good research, such a video just leads to additional questions. Good job. Even if your methods didn't answer every question, good job. For me, the essential thing this demonstrates is that the number of threads biting into the wood is so important. Those style of inserts have fewer threads contacting the wood. They fail sooner when abused slightly.
This was interesting.
I would like like to see you repeat all these tests, but with a board in between the threaded board and the bolt head. Because normally you would not have the bolt head is not in direct contact with the threads.
Suman your analysis is amazing. I love your tests. Keep em coming!
All of this is so crazy - it’s just nuts!
Great comparison Test! Love your control of parameters (thread, thread depth, and wood type) and sample size!
would love to see different types of wood (and mdf, plywood, particleboard) and possibly different directions of wood grain
Wow! This is one of those channels you are glad to have pop up in your feed.
What an interesting experiment. Honestly, have never tried to put those inserts in really harsh conditions but I've alsways considered them as something sturdy and reliable.
Thanks a lot for putting this into test.
Thank you for that. Not at all what I expected. I'll certainly consider that next time I'm reaching for inserts.
Wow!!! This is intriguing information, and your testing methods are superb!!! BRAVO!!!
Fascinating, thanks 👍. I never would have thought that there would be such a difference. I will try it out one day.
A REALLY good assessment, with some very surprising results.
Love your methodological approach. Come for the science, stay for the data.
… A new subscriber
Better read all the comments my friend
Surprising results. Glad i subscribed earlier today (after seeing Scott LoL) just teasing. Love the video
🤣
Well designed study that gives good data, even with a small sample size. Very interesting, will look forwards to seeing more videos like this!
Thanks! Glad you liked it. I wish I could do higher sample size but it takes soo much longer haha.
Sampling is a thing. As long as it's done correctly, no need to waste time.
Great video Suman! I recently read an article in an old version of FWW where Michael Fortune described his process for making wood tapped threads with CA glue for many of his jigs. Your video reinforces why he did!
Suman! Great to see you back on the channel. Hope the family is doing well.
This is a very well performed series of tests and presentation of your data. It's something I've been curious about, and now I'm convinced.
If you're going to continue testing, I would be interested to see performance of different wood glue on different wood species and in different grain-to-grain applications. I think the initial performance might produce useful data, and then if you glue a duplicate set of test pieces to repeat the tests again in a year, then the expansion and contraction effects through 4 seasons on the glue hold may produce different results.
Thanks Aaron! Great idea! I should consider going long term seasonal type tests and think ahead. I definitely have one in the pipeline on waterpoof and one on "oily" wood and glue performance. Taking some notes from your comment for possible future use. Appreciate you coming back to the channel! Great to hear from you
That is a surprising result. Pretty cool video, thanks.
Good job, Suman. Very interesting content presented clearly and succinctly.
This included surprising and interesting results. Thanks for the great video.
I appreciate the scientific and statistical rigor in this video. I'm curious to know if there are brands of inserts that do better than this.
Great video! I'm a sucker for graphs and well presented data. Just took me a second to get used to the non-SI units 😂
I really appreciate this episode. The test actually did change my mind on this subject ~ and well conducted for most use-cases.... Well done sir., 😎
I use inserts when connecting neck to body...never even thought of wood tap! thanks!!!!
Very interesting! I never would have guessed! Another test idea; where I have access to the back side of the wood, and in places where it cosmetically doesn't matter, I have used tee nuts. These are incredibly strong IMO and easy to use, and pretty cheap when bought in bulk. Example; I have a piece of 3/4" plywood hinged at the floor in the doorway of my outdoor building. I originally used wood screws in the hinges and they stripped almost immediately. The tee nuts i replaced them with have been in place at least 15 years and still holding strong.
This was a brilliant video. Thank you for the well thought out and excellent presentation!
As a cabinetmaker, I was not surprised with your results but it was certainly interesting to get actual figures on the results; thank you. As for the title, contrary to some opinions, I think it was appropriate to the demonstration; there IS a problem with metal insets, they are handy, cheap but essentially weak.
Excellent video! I've always wondered about wood tapped threads with CA!
Good video brother. Nice to see content that actually contributes to the bucket of knowledge
Much appreciated. Thank you. The next video is just as interesting. Finishing it up soon :)
A very interesting result. 2 comments as I think through this problem. Having the threaded insert fail is probably easier to repair than having the wood fail. Though at almost double the straight pulling force that seems like a no brainer. I wonder if sheer testing would fair similarly. Secondly, i do think 2 part epoxy is a better fixative for threaded inserts than ca glue, but based on these failures i would be curious if the difference would be noticeable. I trust threaded wood a lot more now based on this testing so than you for that, it is a great result indeed.
Great video. I'm curious what the results would be in plywood or particle board.
Great video. Good to see you back!
That is really fascinating and useful! Very thought provoking. Thanks so much! The only downside from just tapping the wood is the pullout failure mode. If the unglued threaded insert pulls out, you can drill it out, glue in a dowel, reinsert the threaded insert and be good to go. Much harder to recover from a failure of the tapped bolt (and maybe the glued insert too). But all around a great video!
Thanksn I think they both will have the same issue in the event of replacements. Because the threaded inserts fail between the outer thread and the wood, you’d need to reconcile the size of the pilot hole (upsize insert or plug and re-drill). Similarly, if the wood tapped thread fails, you can always upsize the hole and tap a bigger thread or apply the same plug and re-tap method. Just need to be mindful with grain orientation.
@@WoodcraftBySuman Hi! It looks like for the unglued insert pullout failure, yes you need to drill it out a little bigger, then just glue in a wooden dowel, then redrill to the original pilot hole size and reinsert the insert. Really the same as a typical stripped screw repair. The hole left at failure is fairly clean with little to no surrounding damage. For the failure of the tapped holes the board blows apart. Far too much damage to just drill out and insert a dowel and redrill.
At least that is how it looked to me.
As a cranky old guy I've got to say what I'm thinking. This video is such a load of... Great Content!!! Nice job and thanks for the in depth look. I wonder what strenght relationship small diameter-small threads is to large diameter-large threads.... The metal threaded inserts that failed are large/large. Maybe next video?
Great testing. Saved me time, money and produced a better outcome. Thank You!
Glad it helped! Thank you for letting me know
I agree with your results. Provided i have enough depth i alway cut threads into the hard woods. MDF also behaves similarly with hardwoods. The amount of torque a 2-3 cm deep screw in mdf is surprising.
Cool vid! Results are definitely opposite of what I expected.
Perfect timing man! Just saved me a bunch of time and money 👌🏼
I'm sold! Wish you would have taken more footage of making wood tapped threads! Any other videos?
Thanks Daniel. Unfortunately no. But if you DM me on Instagram, I can send you some video of cutting those taps. It really is as simple as drilling a hole and then driving the two through.
Great video. I recently used some similar 1/4"-20 threaded inserts, also in cherry, and was surprised by how easily it stripped out while just installing them. Some of the inserts recommend different sized holes for different woods. I wonder how it would compare if you repeated this with a smaller hole for the inserts. And how different glues compare. I like to use a small hole and ease the friction with wood glue.
Project Farm will be proud of you, lol. Good tests. One of the recommendations for further related test, try this with particle or mdf boards (like IKEA). Though I doubt you can even tap the board, just insert test maybe?
I know this is an old video but.. I cant help wondering if the inserts were actually manufactured metric hence the closest imperial threaded hole had too much run-out?
Actually, all the wood inserts I've used have been self-tapping.
Mate! I’m so surprised by these results, so cool you tested it. Seems like I need to get myself some taps 😂
No need. Ya mum already tapped your head 😜
@@WoodcraftBySuman Haha that makes no sense Suman 😂
@@monkeyboysworkshop aww man. I thought it might have meant something rude to ya brits. Lol
There was a similar test made for 3d printed plastic by i think CNC kitchen with the ourcome that just screwing into plasric is that much more durable than a special threaded insert. But experience says that the threaded insert in this use is simply much nicer because it makes assembly smooth and easy, and also it doesn't cross thread on repeat use, you can just screw in blindly rather than having to carefully find the thread every time.
In wood i will continue using threaded inserts as well. Because the failure is really benign when it happens, i just epoxy the insert right back in and I'm good.
I appreciated this analysis. I look forward to more like this.
You put an incredible effort in that amazing video. Thank you. Very helpful 👍