a lutherie trick: it's better to have slightly rough surfaces in the contact/glue area, especially with woods that are difficult to joint (due to their high oil content). It does not hurt to make small "scratches" in the areas before joining, especially on processed boards (mdf, plywood, etc)
If you are concerned about dry-squeeze then yes. Otherwise there is nothing to be gained with ordinary electrochemical glues as the wood is aready the weakest link. Any thickness above minimum will decrease the strength of the glue part of the joint. For glues that rely on mechanical tack (plastics typically) it is advantageous.
I disagree. Regular wood glue is not gap-filling, and you get the strongest bond with _smooth_ faces in perfect contact with each other. That's why we have jointers. With your technique, you should use certain types of construction adhesive (e.g. Liquid Nails) or epoxy with fillers appropriate to the gap size.
One of the main advantages of morris and tenon joinery was before glue was commonly used. A mortise and tenon can be pegged and will be quite strong with no glue at all. Try that with the other joints.
The Bridle Joint can have a 1" x 1" square thru hole cut in the center of it and a square peg with an interference fit hammered home and cut off on each side with a flat saw just like a Mortice and Tenon joint. Maybe Scott can test that. Also two or more round pegs can secure a Bridle Joint like an M&T joint or similar to the way machinists squares are joined together two, three, or four steel pins. I still enjoy the M&T joints though.
This is alot to ask of one guy, but I'd like to see some testing of different variables in a joint. I always make my mortises with at least half an inch to the endgrain side for instance, and I'm curious about the kind of difference that makes.
I appreciate that you hit on the gripe I have about all of these "OMG STRONGEST JOINT" videos, going back to Matthias' seminal video. Use a joint that's strong enough, meets the aesthetics of what you're making, and will last the desired lifespan of the part. I see no problem with some pocket screws and plywood for workbench drawers, but I wouldn't use it for (hopefully) heirloom furniture. There's no one size fits all joinery and that's part of the fun ;)
Mortise and Tenon joints were considered the "strongest" for a reason - they last. Lap-joints certainly are stronger but in general they will fail earlier as they are fully reliant (in most configurations) on the strength of the glue. So when seasonal changes in temperature and humidity slowly degrade the glue the Lap-join will just fall apart. Where as the Mortise will still hold together decently even without any glue. Mortise is also stronger against loads in other directions. But the joints that are nearly always the weakest are the butt- and miter-joint. They are just inherently weaker as they do not have a mechanical locking nor a lot of surface nor continuous grain. Of course to everything there are exceptions. If you have something like say a house-frame then one of the best ways to connect a horizontal top-plate to the vertical struts is just ... laying it flat on top - a butt joint. For the loads it will have to withstand this is just the strongest it can get.
Thank you for that write-up. I often wonder why there is no focus on how glue holds up over the years. I understand that is hard to test for a youtube channel, but by not discussing it, I feel it is simply a subject intentionally glanced over because it is inconvenient. I know modern glues are really strong, but do they keep strong?
@@KrahsThe "but do they keep strong?" Depends on the glue and situation. In general yes - as most of our furniture is indoors where the temperature and humidity is relatively stable, specially when compared to say 200 years ago. More stable glue and climate make it last far longer.
@@WompWompWoooomp Doweling lap - which direction? if there is a rotational moment then the dowel can certainly help hold it together. And bridle joint is my favourite anyways (together with simple lap-joints). But for both - they will not just fall apart as easily as a lap-joint, but for the bridle it really depends on the load it experiences: Pulling apart or rotating out? Doesn't fair much better once the glue is broken.
Great comment. Years ago I made a garden gate out of 2x4s. (Not pressure treated).. Each corner was a wedged mortise and tennon and I added a diagonal brace that I dovetailed into place. I only used glue to "hold it together ".. the glue failed in the first season or two but that cheesey little gate stayed together and functioning for years till it rotted to pieces.
You can have taller hair in the new shop! My joint test was to build a workbench with tool storage, put hundreds of pounds of tools in it and load it into a container. The container went by truck, rail, ship, barge and truck from NC to Hawaii. Then 5 years later, to CO. In between, I used it as a workbench. Wedged M&T joints are fine 20 years later.
This video is as solid as a combo half-lap/bridal/mortise and tenon joint with 3 hickory dowels. Well done! Looking forward to seeing more of your new garage shop.
I was going to mention the dowels. 🤬 You stole my thunder. NaYa. By dowels I mean from side to side not internally. Drawboard style. Even the splined mitre, IMHO, can be tarted up with two (or more 😳), contrasting dowels either side of the mitre but through the spline can look great. 🤩
I think its misleading to say that the bridle and half lap are stronger than the mortise and tenon. They are stronger for a force coming from that specific direction, but a mortise and tenon would do better resisting forces from other directions. Joints are held together by glue strength and mechanical interference and the way you are testing these joints puts the half lap and bridle in the best situation, where they have both the advantage of large glue surface area and mechanical interference. If you were put a force in the opposite direction (pressing down of the levered parted of the joint instead of up) you would lose the mechanical interference and just rely on the glue strength. In fact in the six possible directions (up, down, left, right, towards, away) the half lap only has mechanical interference in two directions (up and towards), a bridle has mechanical interference in three directions (up, towards and away) and a mortise and tenon has mechanical interference in 5 (up, down, towards, away and left). If you put a dowel in your mortise and tenon it has mechanical interference in all six directions. This is why it is a joint you can use even without glue and why it is so popular for pieces of furniture which will experience forces from several different directions. Obviously the bridle and half lap have their place and they will likely stand up fine in a piece of furniture, but you shouldn't think of them as a 1-to-1 improvement over a mortise and tenon.
They also aren’t directly interchangeable. You can’t use all these things in every situation. Sure I guess if you’re making picture frames you have all these options but when you’re making furniture I fail to see how half laps should be used to make table bases, for example. Maybe I’m not that creative or maybe it’s because m&t is simply the right overall choice in that application.
I recently read something about gluing end grain that is claimed to make it much stronger. The issue with gluing the end grain is that the end grain behaves like a glue sponge and wicks the glue down into the wood and away from the joint, with the result is that critical thin glue layer might not be continuous across the entire joint surface, resulting in a weak joint. The solution offered was to let the end grain soak up as much glue as it wants, and then apply additional glue! To do this, slather glue to the piece with end grain and allow it to sit for 5-10 minutes (but not so long that it starts to dry and set). Then apply additional glue and clamp the joint. This should saturate the end grain with glue so the additional glue stays in the joint space rather than being wicked down into the end grain. I would be very curious if you have heard of this, if you have tried it, and, of course, if it actually makes the joint any stronger.
Try a quick double glue application. I glued some red oak with an end grain glue up, as you know, oak is so straight grained porous you can stick an end in water and blow bubbles. I applied glue, let it wick into the grain, applied again, creating a micro "finger joint" with the glue. As glue is typically stronger than wood, the joint is amazingly strong. Try it for fun. I've found the more the glue wicks into the wood, the stronger the butt joint, the caveat being to make sure the second glue application takes place when the first is still tacky. fun experiment.
Thanks for this. I'm building my library and setting up my shop and tooling now. Looking forward to learning joinery, and it sounds like I'll be doing half laps for my face frames.
I'd use a mortising attachment for a drill press long before plunge cutting with a router. To each his own, I just have my preference. Lately for myself it's been all chisel work following an oscillating cutter, so there's that option too.
Thank you for the (series of) excellent joinery videos. I loved it and I especially liked that you showed homemade jig options for each method. One small point I would like explained further… when you are splining a miter joint isn’t almost all the added strength added to resist “closing the book” vs “opening it”? I would love to see a testing series based on the real world failures of frames. Dropping against a corner, etc Thanks for the awesome videos !
Hey Scott! It was cool meeting you in person last week in Toronto at the Festool event. Another great video. I just tried making a half lap joint last week for the first time, but it’s great to see its strength quantified in relation to other common joints. Looking forward to the next video!
Grwat video! I just made some flat panel quarter-sawn oak cabinet diors using bridle joints, and I'm pretty sure they will last longer than the house they're going to be installed in. 😁
Great job Scott! Interesting results. I know a preponderance of woodworkers focus on joint strength, but is that because we are only seeing the amateur woodworker side on YT? What about the professional woodworker perspective? The TIME == $$ perspective. Do I really need my drawer joints to support 500 lbs of force? What about a utility curve perspective? Time/effort vs strength or another way to say it would be how fast/cheap can I make the joint that's good enough for the purpose? Looking forward the 2nd part video! (the new shop looks great!)
Thanks for these awesome videos. I’m trying to build a fairly basic shelf, except I need it to fit inside of a closet with a small door, so I need to be able to assemble (and hopefully disassemble it when needed) easily inside the closet. Also, I have limited tools, I do have a miter saw, a circular power saw, some chisels that I’m terrible at using. I’m considering getting a router, as they are fairly affordable and don’t take up much storage space, not sure what bits I’d need (and bits seem pricey). I’m trying to avoid buying a table saw, as I don’t have the space for it, and do as few cuts as possible, so I’ll be getting pre-cut 2x4s for the legs (I think) and pre-cut shelves (48x15.75). Since I want it to be easy to assemble and disassemble, I’m trying to avoid screws and angle brackets as much as I can. I’ve been researching wood joints. Thinking something like a half lap or dovetail to prevent the frame that would hold the shelf from sliding in or out of the legs. Also considering trying to do dadoes in the main legs for the shelves to go into, but I’d still need something to make the whole thing stay together, and to stop the shelves from sliding out. Or maybe just a mortise & tenon with some soft of a peg, to stop it from sliding out for the long way part of the frame, and maybe halved lap joint for the short way to hold it all together. Hopefully this makes sense, any suggestions for joints and tools needed?
With the same glue strength per area, a miter should theoretically be twice as rigid as a butt joint due to the square root of 2 times the gluing area and the square root of 2 times the joint leverage due to the wider surface trading force for distance. Also due to this effect, corner spline miters may be stronger in push than in pull, unless you use a massive spline that goes all the way across the joint.
Soooo... Bridle Joint, about twice as difficult to get that glue down in the crack (without a special jig), and just barely stronger than Half Lap. Got it! 😆 And you can EASILY make a Half Lap on any CNC even. So a fancy table saw is not even needed. 😆
My experience restoring furniture, particularly chairs where the joints are put at challenge, is that the main joint used is mortice and tenon and the most common failure is glue related, then tenon related and very few was mortice failures. This makes me think that if you want something that lasts a long time mortice and tenon is the way to go and to make a tenon ticker then the canon 1/3 is a wise practice. I found some pegged or wedged tenon joints without any glue older then a century in perfect shape, I doubt that any joint that relies on glue can last so long as with time the glue cristalizes and becomes brittle so can not cope with the seasonal movements of the wood. If the goal is to build something that is very strong but does not have to last a long time then rely on glue is a sound practice so in this case tests like this one can help, while I doubt that can help if we build something that is made to last a long time, an example is the miter joint if used in a frame, the wood expanding and contracting due to seasonal changes will constantly change the angle from the perfect 45° we build and a glue failure will happen.
A nice test of the common flat joints. Since I make a lot of boxes, I'm looking forward to your upright joint tests. Though I will say that since I'm not making wooden strongboxes, I still mostly use the easier to construct splined half-lap upright joints for the corners. Yes, I'm sure finger joints (which I think are ugly) and dovetail joints (way cool, but with high skill & time requirements) are stronger, the modest half-lap, reinforced with structural AND decorative splines, is strong enough for my use. It's also easy to cut rabbets along the top and bottom edges of the side pieces for the inserted lid and bottom. richard -- “Everything that needs to be said has already been said. But since no one was listening, everything must be said again.” - André Gide
Scot...Great to see a fellow CDN 🇨🇦🇨🇦🇨🇦 woodworker online...grand You Tube videos!! Have learned a lot...& you saved me from diving into a Domino kit!! Is there a link to David "Presutti's" Miter sled build?
Forgive me if this was pointed out, but keep in mind the distance from the joint where the jack presses changes the leverage it gains. As long as it is consistent, the measured break results should be relatively true. But I noticed in the teaser clip of a different joint, that the jack was about 1/2 closer to the joint. This result will not be true, relative to the others. I hope that makes sense… Love the video, though!
Half lap because it's more versatile when creating angled joints end to end joints. And it's way easier to make. Lets say, make an octagonal frame, or unorthodox angles. You can easily lap any angle and just router/saw out the excess protrusions after it's cured. Minor gaps wouldn't be a problem because there's a large area of contact.
I love the look of the bridle and half lap but the mortise and tenon has another longevity benefit that might not ever actually matter, but m&t holds together on the ends when other joints might pull away from humidity. that's because the m&t has that enclosed wood framing. It could split but that would require force that would also pull the other joints away too.
Not all joints are equal, but "by how much" is tricky to tell. The tests I see treat the joint as a monolithic structure. In fact, it is composed of many micro-elements. So when the splined miter is tested in a mode (compression, or pushing the two ends together; vs. tension, pulling the two ends apart), you have to examine the elements. External compression of a joint creates both compression and tension in the wood; likewise, tension test of a joint also creates both tension and compression elements in the wood, but the locations are different (of course). The role of the spline changes depending on whether the wood at the spline is in tension or compression. A spline doesn't help much when it's in compression; but when in tension, the spline can enlarge the stress area, allowing more stress before failure. The joint is not uniform in its strength direction, and most testing only operates in a single direction, which makes simple conclusions very difficult.
A while ago i started using half-lap joints in typical 2x4 construction and it's amazing just how much stronger things became. Even without glue (just screws) everything is way more rigid since in something like a T shape (and to an extent a regular 90) the end of one board is kept from splitting by the board it's cut into. I use a radial arm saw with a small dado stack in it since boards are often too big to be safely shaped on a table saw.
when you start working with plywood sheets then half laps are super easy to setup as you dont even have to cut them, just lay two pieces on top of each other and have them extend out the width of the joint and voila, instant half laps all over.
Thanks for testing - it's great to see some unexpected results, but mortise in MT joint usually does not goes so close to the end of the board - there should be some "meat" left for joint to hold on.
Very good video Scott. One question, I noticed your joints broke a lot on the actual wood, then the question is: do you think if you use harder wood the joints would be stronger? Maybe another video, hopefully...
Reason you were getting crazy numbers on the box joint was due to the jack being so close to the joint. Double the distance from the jack to the joint, and will break at 1/2 the force. It's like using a torque wrench, longer the handle, the easier it is to turn.
@@ScottWalshWoodworking *shear. Sheer is like a cliff face (nearly vertical), a thin fabric (practically see-through), or unmitigated (sheer delight). I'm excited to see Part 2!
@@haphazard1342just so you know, most of us are on our phones. It’s hard as hell to type on these things and autocorrect gets things wrong more than it does right. So don’t be that guy who points out typos made by our stupid phones. Nobody likes that guy. He didn’t think sheer and shear were the same thing and you’ve helped nobody by being pretentious and giving us definitions and spelling lessons.
In most cases the mortis and tendon is the strongest joint if you apply tension in all directions and also it is a concealed joint as to say not exposing itself this is essential in fine cabinetry
How about the most maligned joint the pocket screw? For case work more than strong enough and quick and easy. I was a little surprised by the strength differences. Thank You
I wish you showed the breaking in more detail. You have two fundamentally different types of failure: The glue, or somewhere that's not the joined surface. Your first miter joint was interesting in that it opened up gradually as you increased the force, rather than breaking suddenly. Your lap joint broke elsewhere, meaning the glue was the strongest part. The bridle joint improved the strength because you had grain going in two directions at right angles, like plywood. This makes it more difficult to pull the fibers apart in one of the legs. Also, note that you can make a lap joint that looks like a miter, on one side.
The strength of a simple miter joint is good enough for anything, and it looks decent, and if you want to make it look fancy there is such a variety of ways you can do that with spines. I don't think there's any reason to bother with fancy dovetailing and the skill that you have to develop for that when you can do something that looks almost as cool and is as strong.
It's not like some magic would be added as soon as you use mortise, it's all about glue surface and the integrity of each joining piece. Half lap works the best with two identical pieces but that's not the only scenario in woodworking.
I like your miter spline jig. I have an idea to make it more versatile. It appears that it is made for only one width of mitered wood pieces. Why not make one of the angled pieces to slide horizontally to accommodate various widths. Mill a horizontal slot in one of the 45° pieces and add some tee-nuts to the sled. Attach the movable piece to the sled with bolts with knows. To use it, place the workpiece in the jig, move the movable piece to the desired opening and tighten the movable piece.
The traditional tenon width is 4/10. And like with dovetails the single best reason to use it is the ability to forego glue. Heck, if you work with varying degrees of green, like stick chairs, you don't even have to peg the joints.
I'm curious: when is strength a factor? Certainly making a box, certainly not when making a cabinet door frame. Perhaps match the joint type to strength?
3:55 The miter was 2.4 times stronger than the butt. Most of this difference could be explained by the miter joint being 41% longer (=sqrt 2) than a butt joint. Beam bending strength increases with the cube of the beam height. 1.41^3 = 2.7 I suppose the difference could be in the end-edge grain difference and whether the outside corner buckled.
Nice video and a lot of useful information. For bridle joint @14:25 you mentioned that only one setup is sufficient to cut both sides of the joint. I am trying to figure that out. Could you please elaborate or better yet create a dedicated video on how to setup and create a bridle joint? Thanks in advance.
The major difference between butt joints and miters is that end grain allows much greater surface area due to the channels naturally present to accept glue in the end grain, as opposed to the negligible spaces in the surface of the flat of the board.
nice test jig! except it would be better to put the bottle jack outside of the scale to joint pathway, so that the effects of you pumping on the jack handle do not interfere with the measurement.
The advantage of the half lap over the tenon is that you clamp the two sides of the joint together. You don't have that in a tenon joint, so the contact of each surface of it isn't tight.
youtube just randomly suggested you to me, and it was a great reccomendation, you are so interesting to watch and talented, the first video was the flipping coffee table haha
Having the pump jack on the same lever you are measuring the tension pressure, skews the results depending on how hard the pump lever is used. IMO, the pressure results are dubious. The overall results are most likely accurate as which joint is best for certain situations. Mattais Wandel goes through all that. It has also been shown through various videos that the glue is generally stronger than the wood it is binding.
To compare to the lapped joints, you should have made a 'through' morose and tenon, whereby the mortice extends right through the piece of wood and the tenon is as long as the depth of the mortice. This would be more comparable. A short, stubby tenon joint is less strong..
6:58 - maybe i didn't get the joke but a chocolate teapot is a good analogy for something that fails under its intended use. Anyway, all the testing is very much appreciated and unlike so many youtube testers you seem to actually reach for some semblance of a statistical sample.
I think you weren’t supposed to think about it too much. It just sounds weird and unrelated to the topic of woodworking so it seems like a stupid reply from chatGPT. That’s the joke. That being said a chocolate teapot could make a delicious brew assuming it was thick enough to handle the 20 second brew time or it was in a bigger vessel to contain the tea/chocolate mix as it melted.
Hey Scott, thanks for doing this test. Really solid methodology and I always appreciate these tests that challenge conventional methods. Could you say a bit about your clamping technique for the the mortise and tenon joint? Clearly one has to clamp the half lap joint with pressure perpendicular to the faces, but I'm wondering if you used clamps in that way for the M&T. Since the glue is providing the strength of these joints, clamping pressure is theoretically hugely important.
M &T joints are designed to have a substantial pin through them to counteract the torque loads that he is testing. This is a prime example of why people getting their technical information on RUclips are a danger to society.
Following your conclusion about the lap joint leads me wondering if I should have used a version of that for the Shaker entry table I just made for my wife. Being a novice, I struggled to make good mortis and tenon joints. They'll hold together and look fine from the outside, but I sure ain't proud of the quality- it ended up being a hack job. Seeing this video makes me realize I might have been able to use a lap joint to join the apron to the leg (from the inside of the leg), especially since I was going to add corner blocks anyway. (sigh) Any thoughts on that? Thanks!
Isn't your strength test direction wrong? What kind of force applies to a box or frame from inside out? Maybe because of that the miter didn't get more points? I believe so.
No one has answered to my satisfaction just how strong a joint has to be and for what application. I wouldn't want a butt joint for a bed frame, but it would be just fine for a picture frame. A cabinet made with pocket holes and glue is a modern technique that seems to offer the potential for centuries of utility.
This was awesome man! As an engineer I love data as a woodworker I love wood. I love hand tools and joints so this was right up my alley. Subscribed and this was my first time seeing your stuff! I'm going to describe you to my friends as mclovin the woodworker though.
Great video. Several times it compared surface areas of the different glue joints, but it didn't say where the joint failed. If the joints failed in the wood, where is the evidence that, after a sufficiency, more surface area is "better"? In another words, the glue succeeds as well in a simple joint where the wood breaks as in a more developed joint where the wood breaks. Thank you.
maybe you should test those joineries to their intended orientation of strength or load-bearing characteristics or how it is designed to hold or oppose load and tension. Surely all of those will fail if the force applied is on the opposite side or not the intended directional orientation of the joinery design. And maybe clarify the most suitable uses of each joinery as additional info bits :D
Wonder if you used a half-lap joint and then put a dowel square through afterwards locking them together in the first place - how much stronger that would be??
Sulivan's end grain test is often misunderstood. What he really tested is that the glue up itself is not as weak as people think. Implicitly (though almost overly), what he did was re-affirm what has always been known in the trade rather well for ever. The "strongest joint" for any given application depends on what forces it will be facing, it is all about opposing the geometry of the actual forces a joint will face vs the geometry of wood, glue and hardware. What you want is to create a sitaution that the force is resisted preferentially cross grain (fibers resisting being torn apart) and failling that along the grain in the longest direction (longest amount of chemical bounding between fibers). Try visualizing/drawing the forces in your test set up (no math, just visually and with a bit of common sense), and how they're redistributed by each shape, and it might give you some insight on how you got these numbers here (and would indeed explain why butt joints and end-to-end grain joints are usually garbo in practice).
A glued assembly has to be made so that the glued parts are working in shear stress, and not in traction. Glue isn't effective while stressed in traction mode. Probably explains why the miter joints were bad
Ive noticed that most of these strength tests don't usually include mortise and tennon, half lap or bridal joints with two through dowels as well. That I'd really like to see.
Looking at how the test specimens break in this video, I wouldn't expect through dowels to have any significant effect - I can imagine them both weakening and strenghtening the joint, but not by much. For M&T and bridal through dowels could let you do glueless joints though if you're into that (like traditional Japanese joinery) - just make the dowels from really dry wood and make the fit reasonably tight, and then when air moisture "rehydrates" the wood that dowel is not coming out again (there's a building system called "holz100" using that technique to make gluefree prefab house elements).
For both the M&T and the Bridle joints, what part failed? If the tenon broke then it needs to be thicker - up until the tenon and cheeks break about the same. I also think that approaching 1/2 the thickness would be strongest.
An important point: the solidity of an assembly depend of the proportions: so, if you try with a thicker miter, or if you have a thicker tenon it will be stronger. As you see, the sides of the mortises are 2/3 and tenon is 1/3. The miter you used was perhaps only 1/5 or less. Even, that's widely strong enough to build a furniture.
a lutherie trick: it's better to have slightly rough surfaces in the contact/glue area, especially with woods that are difficult to joint (due to their high oil content). It does not hurt to make small "scratches" in the areas before joining, especially on processed boards (mdf, plywood, etc)
My thoughts, you expose the ends of the fibres and the get glued together across the joint. Almost like a micro finger joint
Rouhg surfaces also have more surface area which increases the strength of the joint.
If you are concerned about dry-squeeze then yes. Otherwise there is nothing to be gained with ordinary electrochemical glues as the wood is aready the weakest link. Any thickness above minimum will decrease the strength of the glue part of the joint. For glues that rely on mechanical tack (plastics typically) it is advantageous.
I disagree. Regular wood glue is not gap-filling, and you get the strongest bond with _smooth_ faces in perfect contact with each other. That's why we have jointers. With your technique, you should use certain types of construction adhesive (e.g. Liquid Nails) or epoxy with fillers appropriate to the gap size.
I used to feel so uncool for making my half lap joints on my table saw because it was easy. Now I can feel quite smug and confident!
spoiler alert! no point watching til the end anymore.
@@The_Nerdy_Electrician Why are you reading comments before watching if not to look for spoilers?
The fact that you use a lap joint puts you above those who can't think past the butt joint.
@jjbailey01 I'd like to see the mortise vs half lap mid way down the board
Smug CONFIDENCE _can_ become your greatest ASSET 👍👍!
One of the main advantages of morris and tenon joinery was before glue was commonly used. A mortise and tenon can be pegged and will be quite strong with no glue at all. Try that with the other joints.
The Bridle Joint can have a 1" x 1" square thru hole cut in the center of it and a square peg with an interference fit hammered home and cut off on each side with a flat saw just like a Mortice and Tenon joint. Maybe Scott can test that. Also two or more round pegs can secure a Bridle Joint like an M&T joint or similar to the way machinists squares are joined together two, three, or four steel pins. I still enjoy the M&T joints though.
@@chrisdaniel1339
You are never going to use a bridle on a table or frame.
@@Art-is-craft If you say so
@@chrisdaniel1339
It is not used traditionally for cabinet frames or tables.
This is alot to ask of one guy, but I'd like to see some testing of different variables in a joint. I always make my mortises with at least half an inch to the endgrain side for instance, and I'm curious about the kind of difference that makes.
I appreciate that you hit on the gripe I have about all of these "OMG STRONGEST JOINT" videos, going back to Matthias' seminal video. Use a joint that's strong enough, meets the aesthetics of what you're making, and will last the desired lifespan of the part. I see no problem with some pocket screws and plywood for workbench drawers, but I wouldn't use it for (hopefully) heirloom furniture. There's no one size fits all joinery and that's part of the fun ;)
He used a 1/4" bit for the mortise. Come on now.
Mortise and Tenon joints were considered the "strongest" for a reason - they last.
Lap-joints certainly are stronger but in general they will fail earlier as they are fully reliant (in most configurations) on the strength of the glue. So when seasonal changes in temperature and humidity slowly degrade the glue the Lap-join will just fall apart. Where as the Mortise will still hold together decently even without any glue. Mortise is also stronger against loads in other directions.
But the joints that are nearly always the weakest are the butt- and miter-joint. They are just inherently weaker as they do not have a mechanical locking nor a lot of surface nor continuous grain. Of course to everything there are exceptions. If you have something like say a house-frame then one of the best ways to connect a horizontal top-plate to the vertical struts is just ... laying it flat on top - a butt joint. For the loads it will have to withstand this is just the strongest it can get.
Thank you for that write-up. I often wonder why there is no focus on how glue holds up over the years. I understand that is hard to test for a youtube channel, but by not discussing it, I feel it is simply a subject intentionally glanced over because it is inconvenient. I know modern glues are really strong, but do they keep strong?
Any thoughts on doweling lap and bridle joints?
@@KrahsThe "but do they keep strong?"
Depends on the glue and situation. In general yes - as most of our furniture is indoors where the temperature and humidity is relatively stable, specially when compared to say 200 years ago. More stable glue and climate make it last far longer.
@@WompWompWoooomp Doweling lap - which direction? if there is a rotational moment then the dowel can certainly help hold it together.
And bridle joint is my favourite anyways (together with simple lap-joints).
But for both - they will not just fall apart as easily as a lap-joint, but for the bridle it really depends on the load it experiences: Pulling apart or rotating out? Doesn't fair much better once the glue is broken.
Great comment. Years ago I made a garden gate out of 2x4s. (Not pressure treated).. Each corner was a wedged mortise and tennon and I added a diagonal brace that I dovetailed into place. I only used glue to "hold it together ".. the glue failed in the first season or two but that cheesey little gate stayed together and functioning for years till it rotted to pieces.
You can have taller hair in the new shop! My joint test was to build a workbench with tool storage, put hundreds of pounds of tools in it and load it into a container. The container went by truck, rail, ship, barge and truck from NC to Hawaii. Then 5 years later, to CO. In between, I used it as a workbench. Wedged M&T joints are fine 20 years later.
This video is as solid as a combo half-lap/bridal/mortise and tenon joint with 3 hickory dowels. Well done! Looking forward to seeing more of your new garage shop.
I was going to mention the dowels. 🤬 You stole my thunder. NaYa.
By dowels I mean from side to side not internally. Drawboard style. Even the splined mitre, IMHO, can be tarted up with two (or more 😳), contrasting dowels either side of the mitre but through the spline can look great. 🤩
@@DB-thats-me drive them dowels at an angle and you won't care about the glue failing. 'sides, ellipses are cooler than the circles.
I think its misleading to say that the bridle and half lap are stronger than the mortise and tenon. They are stronger for a force coming from that specific direction, but a mortise and tenon would do better resisting forces from other directions. Joints are held together by glue strength and mechanical interference and the way you are testing these joints puts the half lap and bridle in the best situation, where they have both the advantage of large glue surface area and mechanical interference. If you were put a force in the opposite direction (pressing down of the levered parted of the joint instead of up) you would lose the mechanical interference and just rely on the glue strength. In fact in the six possible directions (up, down, left, right, towards, away) the half lap only has mechanical interference in two directions (up and towards), a bridle has mechanical interference in three directions (up, towards and away) and a mortise and tenon has mechanical interference in 5 (up, down, towards, away and left). If you put a dowel in your mortise and tenon it has mechanical interference in all six directions. This is why it is a joint you can use even without glue and why it is so popular for pieces of furniture which will experience forces from several different directions.
Obviously the bridle and half lap have their place and they will likely stand up fine in a piece of furniture, but you shouldn't think of them as a 1-to-1 improvement over a mortise and tenon.
They also aren’t directly interchangeable. You can’t use all these things in every situation.
Sure I guess if you’re making picture frames you have all these options but when you’re making furniture I fail to see how half laps should be used to make table bases, for example. Maybe I’m not that creative or maybe it’s because m&t is simply the right overall choice in that application.
I recently read something about gluing end grain that is claimed to make it much stronger. The issue with gluing the end grain is that the end grain behaves like a glue sponge and wicks the glue down into the wood and away from the joint, with the result is that critical thin glue layer might not be continuous across the entire joint surface, resulting in a weak joint.
The solution offered was to let the end grain soak up as much glue as it wants, and then apply additional glue! To do this, slather glue to the piece with end grain and allow it to sit for 5-10 minutes (but not so long that it starts to dry and set). Then apply additional glue and clamp the joint. This should saturate the end grain with glue so the additional glue stays in the joint space rather than being wicked down into the end grain.
I would be very curious if you have heard of this, if you have tried it, and, of course, if it actually makes the joint any stronger.
Yes! I've tried it on a test piece of just some 2x4 spruce about 8 inches long. Definitely makes a strong joint, I can't break it by stomping on it.
Try a quick double glue application. I glued some red oak with an end grain glue up, as you know, oak is so straight grained porous you can stick an end in water and blow bubbles. I applied glue, let it wick into the grain, applied again, creating a micro "finger joint" with the glue. As glue is typically stronger than wood, the joint is amazingly strong. Try it for fun. I've found the more the glue wicks into the wood, the stronger the butt joint, the caveat being to make sure the second glue application takes place when the first is still tacky. fun experiment.
The new shop is looking great. I especially like the wood roll up door. Looking forward to the next installment.
Thanks for this. I'm building my library and setting up my shop and tooling now. Looking forward to learning joinery, and it sounds like I'll be doing half laps for my face frames.
I'd use a mortising attachment for a drill press long before plunge cutting with a router. To each his own, I just have my preference. Lately for myself it's been all chisel work following an oscillating cutter, so there's that option too.
Thank you for the (series of) excellent joinery videos. I loved it and I especially liked that you showed homemade jig options for each method.
One small point I would like explained further… when you are splining a miter joint isn’t almost all the added strength added to resist “closing the book” vs “opening it”? I would love to see a testing series based on the real world failures of frames. Dropping against a corner, etc
Thanks for the awesome videos !
Hey Scott! It was cool meeting you in person last week in Toronto at the Festool event. Another great video. I just tried making a half lap joint last week for the first time, but it’s great to see its strength quantified in relation to other common joints. Looking forward to the next video!
It was great chatting with you Aaron! Cheers!
Grwat video! I just made some flat panel quarter-sawn oak cabinet diors using bridle joints, and I'm pretty sure they will last longer than the house they're going to be installed in. 😁
Great job Scott! Interesting results. I know a preponderance of woodworkers focus on joint strength, but is that because we are only seeing the amateur woodworker side on YT? What about the professional woodworker perspective? The TIME == $$ perspective. Do I really need my drawer joints to support 500 lbs of force? What about a utility curve perspective? Time/effort vs strength or another way to say it would be how fast/cheap can I make the joint that's good enough for the purpose? Looking forward the 2nd part video! (the new shop looks great!)
Thanks for these awesome videos. I’m trying to build a fairly basic shelf, except I need it to fit inside of a closet with a small door, so I need to be able to assemble (and hopefully disassemble it when needed) easily inside the closet. Also, I have limited tools, I do have a miter saw, a circular power saw, some chisels that I’m terrible at using. I’m considering getting a router, as they are fairly affordable and don’t take up much storage space, not sure what bits I’d need (and bits seem pricey). I’m trying to avoid buying a table saw, as I don’t have the space for it, and do as few cuts as possible, so I’ll be getting pre-cut 2x4s for the legs (I think) and pre-cut shelves (48x15.75). Since I want it to be easy to assemble and disassemble, I’m trying to avoid screws and angle brackets as much as I can. I’ve been researching wood joints. Thinking something like a half lap or dovetail to prevent the frame that would hold the shelf from sliding in or out of the legs. Also considering trying to do dadoes in the main legs for the shelves to go into, but I’d still need something to make the whole thing stay together, and to stop the shelves from sliding out. Or maybe just a mortise & tenon with some soft of a peg, to stop it from sliding out for the long way part of the frame, and maybe halved lap joint for the short way to hold it all together. Hopefully this makes sense, any suggestions for joints and tools needed?
As always, thanks for the video. I need to go through and watch all of your sled/jig videos. Appreciate your time sir.
Great video. Thanks. I would have liked your conclusion on the experiment. Perhaps, strength vs. effort?
With the same glue strength per area, a miter should theoretically be twice as rigid as a butt joint due to the square root of 2 times the gluing area and the square root of 2 times the joint leverage due to the wider surface trading force for distance. Also due to this effect, corner spline miters may be stronger in push than in pull, unless you use a massive spline that goes all the way across the joint.
Soooo... Bridle Joint, about twice as difficult to get that glue down in the crack (without a special jig), and just barely stronger than Half Lap. Got it! 😆 And you can EASILY make a Half Lap on any CNC even. So a fancy table saw is not even needed. 😆
"because no one knows how much effort we put into anything, it's the ultimate joint" 😂
My experience restoring furniture, particularly chairs where the joints are put at challenge, is that the main joint used is mortice and tenon and the most common failure is glue related, then tenon related and very few was mortice failures. This makes me think that if you want something that lasts a long time mortice and tenon is the way to go and to make a tenon ticker then the canon 1/3 is a wise practice. I found some pegged or wedged tenon joints without any glue older then a century in perfect shape, I doubt that any joint that relies on glue can last so long as with time the glue cristalizes and becomes brittle so can not cope with the seasonal movements of the wood. If the goal is to build something that is very strong but does not have to last a long time then rely on glue is a sound practice so in this case tests like this one can help, while I doubt that can help if we build something that is made to last a long time, an example is the miter joint if used in a frame, the wood expanding and contracting due to seasonal changes will constantly change the angle from the perfect 45° we build and a glue failure will happen.
A nice test of the common flat joints. Since I make a lot of boxes, I'm looking forward to your upright joint tests. Though I will say that since I'm not making wooden strongboxes, I still mostly use the easier to construct splined half-lap upright joints for the corners. Yes, I'm sure finger joints (which I think are ugly) and dovetail joints (way cool, but with high skill & time requirements) are stronger, the modest half-lap, reinforced with structural AND decorative splines, is strong enough for my use. It's also easy to cut rabbets along the top and bottom edges of the side pieces for the inserted lid and bottom.
richard
--
“Everything that needs to be said has already been said. But since no one was listening, everything must be said again.”
- André Gide
Scot...Great to see a fellow CDN 🇨🇦🇨🇦🇨🇦 woodworker online...grand You Tube videos!! Have learned a lot...& you saved me from diving into a Domino kit!! Is there a link to David "Presutti's" Miter sled build?
As I see at 11:48 you didn't brake the L-frame only, but the fixture wood above it as well. This caused so high force. It is not correct exoeriment.
Forgive me if this was pointed out, but keep in mind the distance from the joint where the jack presses changes the leverage it gains. As long as it is consistent, the measured break results should be relatively true. But I noticed in the teaser clip of a different joint, that the jack was about 1/2 closer to the joint. This result will not be true, relative to the others.
I hope that makes sense…
Love the video, though!
Never had good luck with a lap joint. I definitely like the spline and will use it. Thank you for testing.
Half lap because it's more versatile when creating angled joints end to end joints. And it's way easier to make. Lets say, make an octagonal frame, or unorthodox angles. You can easily lap any angle and just router/saw out the excess protrusions after it's cured. Minor gaps wouldn't be a problem because there's a large area of contact.
I love the look of the bridle and half lap but the mortise and tenon has another longevity benefit that might not ever actually matter, but m&t holds together on the ends when other joints might pull away from humidity. that's because the m&t has that enclosed wood framing. It could split but that would require force that would also pull the other joints away too.
Not all joints are equal, but "by how much" is tricky to tell. The tests I see treat the joint as a monolithic structure. In fact, it is composed of many micro-elements. So when the splined miter is tested in a mode (compression, or pushing the two ends together; vs. tension, pulling the two ends apart), you have to examine the elements. External compression of a joint creates both compression and tension in the wood; likewise, tension test of a joint also creates both tension and compression elements in the wood, but the locations are different (of course). The role of the spline changes depending on whether the wood at the spline is in tension or compression. A spline doesn't help much when it's in compression; but when in tension, the spline can enlarge the stress area, allowing more stress before failure. The joint is not uniform in its strength direction, and most testing only operates in a single direction, which makes simple conclusions very difficult.
Nice! I always love watching these woodworking joint testing videos. Also, nice new shop!
Thanks for mentioning Stewart!
It's the sharp inside corner!
A while ago i started using half-lap joints in typical 2x4 construction and it's amazing just how much stronger things became. Even without glue (just screws) everything is way more rigid since in something like a T shape (and to an extent a regular 90) the end of one board is kept from splitting by the board it's cut into. I use a radial arm saw with a small dado stack in it since boards are often too big to be safely shaped on a table saw.
when you start working with plywood sheets then half laps are super easy to setup as you dont even have to cut them, just lay two pieces on top of each other and have them extend out the width of the joint and voila, instant half laps all over.
This was a lovely video. Your beauty shots of all your joints are fantastic. Some nice tips and tricks sprinkled in.
Missed your videos Scott, glad to have you back!
I would've loved to see half lap + dowel combo. I think it is insanely strong!
Thanks for testing - it's great to see some unexpected results, but mortise in MT joint usually does not goes so close to the end of the board - there should be some "meat" left for joint to hold on.
Very good video Scott. One question, I noticed your joints broke a lot on the actual wood, then the question is: do you think if you use harder wood the joints would be stronger? Maybe another video, hopefully...
A "chocolate teapot" actually makes perfect sense. It is a thing intended to hold hot liquid, made out of a material that melts very easily.
And it's an existing turn of phrase in some regions, so ChatGPT didn't even come up with it itself
Swert and tempting, but absolutely impractical.
A chocolate teapot will work if the tea water is cool or if using hot water, the tea is made in a freezer.
@@maplebones I like the outside the box thinking, but I'm looking forward to the youtube video where you test the freezer hypothesis. 😀
Thanks Scott! Excellent video. Nice to know easy can be just as good, if not better than, fancy.
Reason you were getting crazy numbers on the box joint was due to the jack being so close to the joint. Double the distance from the jack to the joint, and will break at 1/2 the force. It's like using a torque wrench, longer the handle, the easier it is to turn.
I wrote a blurb about this in the description, but in short, I wanted to do a sheer strength test.
@@ScottWalshWoodworking *shear. Sheer is like a cliff face (nearly vertical), a thin fabric (practically see-through), or unmitigated (sheer delight).
I'm excited to see Part 2!
@@haphazard1342just so you know, most of us are on our phones. It’s hard as hell to type on these things and autocorrect gets things wrong more than it does right.
So don’t be that guy who points out typos made by our stupid phones. Nobody likes that guy. He didn’t think sheer and shear were the same thing and you’ve helped nobody by being pretentious and giving us definitions and spelling lessons.
In most cases the mortis and tendon is the strongest joint if you apply tension in all directions and also it is a concealed joint as to say not exposing itself this is essential in fine cabinetry
How about the most maligned joint the pocket screw? For case work more than strong enough and quick and easy.
I was a little surprised by the strength differences.
Thank You
I wish you showed the breaking in more detail.
You have two fundamentally different types of failure: The glue, or somewhere that's not the joined surface.
Your first miter joint was interesting in that it opened up gradually as you increased the force, rather than breaking suddenly.
Your lap joint broke elsewhere, meaning the glue was the strongest part. The bridle joint improved the strength because you had
grain going in two directions at right angles, like plywood. This makes it more difficult to pull the fibers apart in one of the legs.
Also, note that you can make a lap joint that looks like a miter, on one side.
The strength of a simple miter joint is good enough for anything, and it looks decent, and if you want to make it look fancy there is such a variety of ways you can do that with spines. I don't think there's any reason to bother with fancy dovetailing and the skill that you have to develop for that when you can do something that looks almost as cool and is as strong.
It's not like some magic would be added as soon as you use mortise, it's all about glue surface and the integrity of each joining piece. Half lap works the best with two identical pieces but that's not the only scenario in woodworking.
I like your miter spline jig. I have an idea to make it more versatile. It appears that it is made for only one width of mitered wood pieces. Why not make one of the angled pieces to slide horizontally to accommodate various widths. Mill a horizontal slot in one of the 45° pieces and add some tee-nuts to the sled. Attach the movable piece to the sled with bolts with knows. To use it, place the workpiece in the jig, move the movable piece to the desired opening and tighten the movable piece.
The traditional tenon width is 4/10. And like with dovetails the single best reason to use it is the ability to forego glue. Heck, if you work with varying degrees of green, like stick chairs, you don't even have to peg the joints.
Wonderful video, congrats on the new shop!!
Excellent job! And a pantorouter shot!
I would definitely love to see some tests on differently proportioned mortise and tenon joints at some point, I can't really find any testing online.
I'm curious: when is strength a factor? Certainly making a box, certainly not when making a cabinet door frame. Perhaps match the joint type to strength?
Not sure if it's a new camera, lens filter, or the lights in the new shop but this video is on a new level
Definitely the hair
3:55 The miter was 2.4 times stronger than the butt. Most of this difference could be explained by the miter joint being 41% longer (=sqrt 2) than a butt joint. Beam bending strength increases with the cube of the beam height.
1.41^3 = 2.7
I suppose the difference could be in the end-edge grain difference and whether the outside corner buckled.
Nice video and a lot of useful information. For bridle joint @14:25 you mentioned that only one setup is sufficient to cut both sides of the joint. I am trying to figure that out. Could you please elaborate or better yet create a dedicated video on how to setup and create a bridle joint? Thanks in advance.
Congratulations on the new workshop!
Thanks Pete!
The major difference between butt joints and miters is that end grain allows much greater surface area due to the channels naturally present to accept glue in the end grain, as opposed to the negligible spaces in the surface of the flat of the board.
I´m curious to know if a bent laminated wood would be stronger in this comparison...
nice test jig! except it would be better to put the bottle jack outside of the scale to joint pathway, so that the effects of you pumping on the jack handle do not interfere with the measurement.
Very nice show, dialog content and delivery great.
The advantage of the half lap over the tenon is that you clamp the two sides of the joint together. You don't have that in a tenon joint, so the contact of each surface of it isn't tight.
HE RETURNS! Make more videos please Scott!
Great video! Did you say how long the glue joints set and dried for and what type of glue, as those factors affect the joint strength?
youtube just randomly suggested you to me, and it was a great reccomendation, you are so interesting to watch and talented, the first video was the flipping coffee table haha
Educational and entertaining! Thank you for honoring others who give us test results as well as your own testing, which is credible and invaluable.
I have a Festool Domino, one definitevely don't NEED it, but it makes your life so much easier. I believe it worth it's price.
The other guy's miter splines also went full depth on the miter; yours were limited to a bit over half by your table saw blade.
Do you have a video on your table saw jig?
Thank you very much. That was a very thorough test and most illuminating.
mortise and tenon imho calls for a dowel, preferably with a hole bored little bit offset between pieces to squeeze them together.
and a diagonal brace with 2 more dowels. The offset is to take up shrinkage from green timbers.
A nice addition would be cross dowelling the bridle and lap joints like a draw bore mortice and tenon
Having the pump jack on the same lever you are measuring the tension pressure, skews the results depending on how hard the pump lever is used. IMO, the pressure results are dubious. The overall results are most likely accurate as which joint is best for certain situations. Mattais Wandel goes through all that. It has also been shown through various videos that the glue is generally stronger than the wood it is binding.
To compare to the lapped joints, you should have made a 'through' morose and tenon, whereby the mortice extends right through the piece of wood and the tenon is as long as the depth of the mortice. This would be more comparable. A short, stubby tenon joint is less strong..
6:58 - maybe i didn't get the joke but a chocolate teapot is a good analogy for something that fails under its intended use. Anyway, all the testing is very much appreciated and unlike so many youtube testers you seem to actually reach for some semblance of a statistical sample.
I think you weren’t supposed to think about it too much. It just sounds weird and unrelated to the topic of woodworking so it seems like a stupid reply from chatGPT. That’s the joke.
That being said a chocolate teapot could make a delicious brew assuming it was thick enough to handle the 20 second brew time or it was in a bigger vessel to contain the tea/chocolate mix as it melted.
I've always liked the look of a half-lap with a dowel through it.
Or a mortise and tenon with 1 or 2 dowels through them.
Can you cut the half lap joint in the same manner as the bridle joint? On end instead of laying fown flat?
yeah for sure! It would be pretty easy too because the fence wouldn't have to move for the other side of the joint once dialled in.
You went with 1/4" for the tenon, what about a thicker tenon like 3/8"?? Mortise walls would be thinner, but maybe you win more than you loose?
Hey Scott, thanks for doing this test. Really solid methodology and I always appreciate these tests that challenge conventional methods. Could you say a bit about your clamping technique for the the mortise and tenon joint? Clearly one has to clamp the half lap joint with pressure perpendicular to the faces, but I'm wondering if you used clamps in that way for the M&T. Since the glue is providing the strength of these joints, clamping pressure is theoretically hugely important.
M &T joints are designed to have a substantial pin through them to counteract the torque loads that he is testing. This is a prime example of why people getting their technical information on RUclips are a danger to society.
Following your conclusion about the lap joint leads me wondering if I should have used a version of that for the Shaker entry table I just made for my wife. Being a novice, I struggled to make good mortis and tenon joints. They'll hold together and look fine from the outside, but I sure ain't proud of the quality- it ended up being a hack job. Seeing this video makes me realize I might have been able to use a lap joint to join the apron to the leg (from the inside of the leg), especially since I was going to add corner blocks anyway. (sigh) Any thoughts on that? Thanks!
Just practice the techniques of mortise and tenon to include sawing, chiselling and planing.
Isn't your strength test direction wrong? What kind of force applies to a box or frame from inside out? Maybe because of that the miter didn't get more points? I believe so.
No one has answered to my satisfaction just how strong a joint has to be and for what application. I wouldn't want a butt joint for a bed frame, but it would be just fine for a picture frame. A cabinet made with pocket holes and glue is a modern technique that seems to offer the potential for centuries of utility.
This was awesome man! As an engineer I love data as a woodworker I love wood. I love hand tools and joints so this was right up my alley. Subscribed and this was my first time seeing your stuff! I'm going to describe you to my friends as mclovin the woodworker though.
my high school nickname still chases me
Like your style. Always instructive. Always entertaining.
Great review... Also appreciated your dowel-biscuit-domino comparison video too! 'Butt joint science' .....Awesome.
A vacuum bottle keeps hot things hot, also it keeps cold things cold, but how does it know?
Great video. Several times it compared surface areas of the different glue joints, but it didn't say where the joint failed. If the joints failed in the wood, where is the evidence that, after a sufficiency, more surface area is "better"? In another words, the glue succeeds as well in a simple joint where the wood breaks as in a more developed joint where the wood breaks. Thank you.
maybe you should test those joineries to their intended orientation of strength or load-bearing characteristics or how it is designed to hold or oppose load and tension. Surely all of those will fail if the force applied is on the opposite side or not the intended directional orientation of the joinery design. And maybe clarify the most suitable uses of each joinery as additional info bits :D
Been watching the progress on Instagram. Super excited to watch this
Wonder if you used a half-lap joint and then put a dowel square through afterwards locking them together in the first place - how much stronger that would be??
I do love a good joint.
That is quite the eye opening video! Thanks for posting this very useful info.
Thank you, I will try it
Sulivan's end grain test is often misunderstood. What he really tested is that the glue up itself is not as weak as people think. Implicitly (though almost overly), what he did was re-affirm what has always been known in the trade rather well for ever. The "strongest joint" for any given application depends on what forces it will be facing, it is all about opposing the geometry of the actual forces a joint will face vs the geometry of wood, glue and hardware. What you want is to create a sitaution that the force is resisted preferentially cross grain (fibers resisting being torn apart) and failling that along the grain in the longest direction (longest amount of chemical bounding between fibers). Try visualizing/drawing the forces in your test set up (no math, just visually and with a bit of common sense), and how they're redistributed by each shape, and it might give you some insight on how you got these numbers here (and would indeed explain why butt joints and end-to-end grain joints are usually garbo in practice).
Isn't the difference between butt and miter joint just due to angle of attack when trying to break it + lenght of glued area being 41% larger?
A glued assembly has to be made so that the glued parts are working in shear stress, and not in traction. Glue isn't effective while stressed in traction mode. Probably explains why the miter joints were bad
Splined miter has some area working in shear stress for example
Ive noticed that most of these strength tests don't usually include mortise and tennon, half lap or bridal joints with two through dowels as well. That I'd really like to see.
Looking at how the test specimens break in this video, I wouldn't expect through dowels to have any significant effect - I can imagine them both weakening and strenghtening the joint, but not by much. For M&T and bridal through dowels could let you do glueless joints though if you're into that (like traditional Japanese joinery) - just make the dowels from really dry wood and make the fit reasonably tight, and then when air moisture "rehydrates" the wood that dowel is not coming out again (there's a building system called "holz100" using that technique to make gluefree prefab house elements).
For both the M&T and the Bridle joints, what part failed? If the tenon broke then it needs to be thicker - up until the tenon and cheeks break about the same. I also think that approaching 1/2 the thickness would be strongest.
An important point: the solidity of an assembly depend of the proportions: so, if you try with a thicker miter, or if you have a thicker tenon it will be stronger.
As you see, the sides of the mortises are 2/3 and tenon is 1/3. The miter you used was perhaps only 1/5 or less.
Even, that's widely strong enough to build a furniture.