Mill Scale Removal Shootout: Abrasive methods.
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- Опубликовано: 8 июн 2022
- I hate removing mill scale. It clogs regular grinding discs, so I decided to do a little shootout. NO SPONSORSHIP - just the straight goods on what I found that WORKS.
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throttle-stop-garage.creator-... 
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TSG Words to live by…… “It doesn’t save you money, it just costs you time.” “I need less frustration in my life.” And - Don’t mind the “apprentice marks”. Love it. Thanks for taking the time to show us what doesn’t work. All the best to you….. 👍👍😎👍😎
Thanks...this was really bugging me this week. I just needed to get some work done not mess around with scale!
It does save you money, but it costs you time.
Harbor freight Warrior 4.5 in Poly carbide woven disc. $7.99 before sale price. BAUER Carbide Grit Triangular Grinding Rasp for Oscillating Multi-Tools.
The problem with mill scale is it wants to just burnish or glaze over and you can't get under it. The poly silicon carbide woven wheel are hard enough grit to break thru. Ceramics do too. The triangle carbide grit on the vibration multi tool will break up the scale with a quick pass, then hit with the woven wheel. Use a router speed control to slow down the grinder 11,000 rpm is too fast on scale it glazes, slow it down.
Great tips - haven't had to remove any mill scale in a bit thankfully.
I used 45% vinegar that I bought on Amazon for mill scale on hot rolled 1/2” plate. This worked out very well for me!
It does work great if you can submerse the part! Much easier than grinding.
Always great content! Guys like you should have an unlimited budget to teach young up and comers with all the attitude but none of the wisdom. Would love to hear where your journey started and what guided you to be as good as you are. Not trying to over do it with the praise but you do everything top notch and thoughtfully. Myself As a backyard shadetree basher you are inspiring
Thanks Marc - very kind words indeed. I'll think about doing some sort of retrospective video. I really appreciate the positive feedback. I thought about this all day as I was slugging away on the next project. Not really sure where to start or how to even respond.
Thank you. Useful information is always useful!
Glad it was helpful!
Those orange/purple spongy discs are my go to discs for millscale and rust on tubes...but on sheetmetal or flatbar, millscale is a biach, also you should use backing plate with that "support"washer for angle grinder so the shaft of grinder doest stick out and you can use it flat...much better for finish and disc life
Yup - I've got to grab a washer to get that backing pad flat.
Keep up the great videos!
Thanks, will do!
Hi, I use fiber discs all the time at my job. The Walter cool-cut xx are great. But I've discovered the VSM ceramic, they are better and not as expensive. The better back-up pad makes a big difference in the performance of the disc. I use 5" 50gr for big material removal on steel and 120gr for weld removal on stainless steel.
Thanks for the info!
I think I must the vinegar method.
Being retired time is not a big issue.
Great demo as always.
It really does work - but for larger parts, where am I going to store 10 gallons of vinegar and a tank? The scale just brushes off.
I did buy one of those pferd diamond wire wheels like Fireball Tool uses and it's great, but you need either a variable speed grinder or a buffer/polisher to run it.
Before that, or if I'm working on small parts or sharp parts that'll eat the wire wheel, I use 3m cubitron resin discs 36 grit. Walter, Pferd, BA, Harbor Freight ain't got nothing on cubitron.
True - I've never tried the diamond wire wheel. I've wanted to, but haven't yet.
Spongy discs are great. I did alot of testing with different discs and definitely came to the conclusion that for tube the best is spongy for millscale and cubitron pads 80 grit for surface. 120 grit cubitron actually is amazing for the final finish but I dont think they are easily available. Flap discs SUCK.
Can you grab a brand name for the spongy disks? I've got a stack of the Walter ceramic disks and they're pretty good.
@@ThrottleStopGarage I've used Mirka brand spongy discs. They are alright for the price and very available in Finland. There just isnt that much variety here in spongy discs. With flap discs I noticed that no matter what the price point of disc they all clog up pretty much the same on heavy millscale. I must admit I couldnt justify the price of ceramic flap discs so I havent tried then.
White distilled vinegar works very well, but it takes some preparation with building a suitable tank for larger steel plates or parts, for example with some fish pond liner, or an IBC container cut to a suitable size, or whatever you can find or use that fits your parts. For flat bars or pipes you could use a PVC pipe filled with vinegar. You drop the metal in the tank, let it sit for some time, I don't know, maybe 24 hours or so, maybe shorter, that is a matter of trial and error, and it will be as shiny and as clean as it can get without any abrasive marks on it. But you have to rinse it to stop the chemical process. But compared to abrasive methods it takes no effort at all. And it is very cheap. Even if it is just for one project or part. You can easily do a few tests and it will cost you less than 5 dollars.
I've done this before and it does work great...I just didn't have the time or patience to build a big tank and scour town for gallon jugs of vinegar!
@@ThrottleStopGarage I hear you, but it doesn't even have to be a big tank with gallons of vinegar. If you have some pond liner all you need is a few pieces of wood, or some rocks, to create a temporary raised edge, it doesn't even have to be screwed together, that you can cover with the pond liner and create a bath that is just deep enough and just large enough to cover your part. If your material is only 1 cm in thickness the temporary bath doesn't have to be any deeper than that. I think that for that large flat part that you showed in this video it would take less than a gallon.
There used to be this guy on TV who makes all those impractical steel swords and such. I forgot his name. He does this all the time, I mean with the pond liner. And if you can get your hands on some EPDM roof or pond liner you can use it over and over again, that stuff is nearly impossible to pierce or rip apart. And the EPDM rubber is also excellent material for DIY rubber gaskets. Super strong.
@@insAneTunA I'm going to look around and see if I can find any. Thanks.
@@ThrottleStopGarage It is a material that if you run into it, for example because people are going to replace it, you want to have at least a usable part of it because it is such a versatile material to have, even if it was just for making your own gaskets for various applications. Especially when you need a larger size gasket for whatever application. Years ago I bought a piece that was used as a pond liner but that had a piercing somewhere. For my application that didn't matter at all. And to this date I still use it if I need a gasket that I can't buy or when I think that it is way too expensive.
I had seen some videos about EPDM rubber and they said that it was so strong that you can't rip a sheet apart with your bare hands. I thought that they were exaggerating, so I tried it, but it is true. I could not rip it apart with my bare hands. At least not when I tried it with a substantial piece of it. I'm not the hulk, but I ain't tiny either :-) And EPDM rubber is also used for automotive applications.
Anyway, curious to see if you can find a satisfying and suitable solution for your situation :-)
Trash bags work great. Any plastic, then 12” rope, or dowels. Super easy.
When flexcut wears down , save em for the light scale stuff an they won't bite like they do as new . Can use em to prep sheet metal after warn in
Good to know.
I don't deal much with mill scale but as a blade smith making damascus steel , the scale is much thicker and there is always flux on the billet , to get rid of it in absolutely no time at all , i use the diamond coated tile cutting discs on the 4.5" angle grinder . and they are cheap , costing the equivalent of $3 a disc ! After that i will smooth it off either on my belt grinder or with a flap disc
For sure going to try this!
@@ThrottleStopGarage please let me know if it works as well for your application as it does for mine 👍🏻
I've had good experiences with 3M cubitron which I think is CBM Cubic Boron Nitride - basically cuts faster and lasts way longer than a normal grinding disk. Not sure if that's a finish available on the flap wheels or scourers but that stuff is great. Plus one on flap wheels tending to dig holes and float on the scale. I stripped the scale off the top of a 50mm thick disk a while back, heavy scale, and I did it with paper towels and hydrochlroic acid brushed on and just monitored. Once it got all the way through I hit it with water and a wire wheel and light oil and then later waxed it and it came up great minus the small creases/grooves from the manufacturing process that the acid exposed (filled with scale prior, I guess).
I'll have to see if I can find a cubitron disk. I've used various acids over the years. Works great if I've got patience.
I got some Walter Coolcut in 36 grit and they work great.
@@ThrottleStopGarage I was taken in by the marketing. Cubitron is nothing to do with CBN/Cubic Boron Nitride at all, they're ceramic. I can atest to the fact that they work very very well though and last well. Description is:
engineered with precision-shaped grain to cut faster than competitive ceramic products
Triangular shaped ceramic grain wears evenly, runs cool, and optimizes mineral breakdown, for extra-long life
Guessing other ceramic disks are comparable at least ;-)
The best way to remove millskills to buy metal. That doesn't have it either cold road or factory san blasted. I get cold rolled for my steel signs and I get factory sand blasted for my AR 500 targets. It's cheaper overall because you save money on embraces and more importantly, you save your time.
Absolutely, I try to order cold rolled when I can get it.
Vinegar is pretty good. I keep a 4" x 6' pvc pipe in the corner of my garage, with one welded on cap and one loose cap with vinager in it. I use Home Depot 30% vinegar but I'll add water sometime if I'm low. After an overnight soak, I put 3 2x4's on my pickup bed (my driveway slopes) then lay some poly over them. I pull out the pickled pieces, rub them with a scotch pad, then stand them in a gallon bucket that I've added baking power to and rub them with another scotch pad. I use a piece of mechanics wire like a fish hook to put the metal in the tube and to pull them out. when I rinse, I usually pull the scotch pad through the tube while they are in the baking power bath. After all this the metal gets a hose rinse and then an air blow. Because I'm obsessive, I like to buzz them with 150 grit on my orbital sander. My power coat guy doesn't charge me much for prep. Plates can be done using the poly and 2x4 box method, just think through how you'll empty it. Spilling on my driveway doesn't seem to cause trouble (asphalt) as long as I have the hose ready. 😎😎
That's a great idea. I'm going to think about this for a bit.
Thanks!
Thanks for watching!
I was usually removing most of the big stuff by brushing on a heavy coat of krud cutter - the must for rust and wrapping the part overnight in plastic film so it doesn't dry out. Rinse then grind the little left, which leaves a good finish and does not cost an arm and a leg in abrasives. There's a tiny layer of scale that will be left, so abrasives are needed but most of the heavy stuff is gone at least, it's way softer to grind off.
Great tip!
Phosphoric acid which also is great to prevent surface rust developing.
I've used it - it just takes time and is messy in a home shop.
Nice reference video.
Glad you think so!
thank you for taking the time and money to do this video on mill scale.....
have you ever tried silicon dioxide sanding/grinding discs..they are softer
than aluminum oxide or zirconium and .they fracture
much easier and so have a sharp edge all the time......
they are used for stone and glassand are supposedly great for mill scale and are inexpensive...
.being just a disc....I bought some recently, but have not given them a thorough testing...
my mill scale issues are much heavier than yours as I also work with structural steel
for the industrial looking furniture I make....we normally leave the thin mill scale
on from tubing....as we are powder coating and the powder coaters is blasting these, I think...haha
Best Wishes from Florida....Paul
You're welcome. I've never tried the SiO2 disks but the flex disks for mill scale are soft and wear pretty fast. They work, but have limits.
I have used S/C rock disc's for many years in my fab shop, but you have to break the wheel edge in first otherwise you will gouge the crap out of base metal. I learned this by accident one day when i bought masonry disks and noticed how easy the scale came off,upon looking at the disk I was like "WTF" it was a different brand than the Norton I usually purchased. can't explain why it works but it does, but to be honest most fab jobs I do are MIG welded heavy structural steel like cat walks, platforms for plastic injection molding machine ect. mill scale isn't an issue., but weldment critical NDT jobs get proper prep work as per spec.
Not sure why you didn't have luck with the S/C disk you tryed, maybe it was the grit? I use 60
Cool - I'm going to try this! Thanks.
*must try
Also try 36 grit ceramic fibre disks (like the 80 grit I used). I tried them this morning on the advice of a viewer and it worked fine.
Vinegar 1 week in a kids blue pool no grinding... try it works great!
Thanks for the tip!
YOU HELP AND YOU HELP BIG.. don't ever have to defend your actions Sir..
Thanks. I don't rant often, but there are enough sales videos that are all sunshine rainbows for products that just don't work.
Silicon carbide flap discs supposedly work very well. Pferd also makes a wire cup wheel with an industrial diamond coating for mill scale but it's prohibitively expensive and if it holds up like their other wire wheels it'd be a waste of money.
Can't find those at all - I did find that 36 grit fibre sanding disks (ceramic) work as well as the flexcut. Those would be my top two options for rapid, inexpensive removal of heavy mill scale.
Amazon! Got a box of 10 for like 30 bucks!
I can vouche for the Si-Ca flap disks. They are usually sold as "used on masonry" , but they work wonders on heavier millscale too. For lighter jobs I like the Purple/black paint strippers cause they don't gouge.
Abrasives are good for a quick clean welding job but for production get a plastic tank at a farm supplier and put water and muriatic acid. You can put all the parts in there, go get some coffee come back and they are clean with no gouging
Great tip.
Are there chemical solutions?
(Something like rust converters?)
Yes - many acids will do the trick. Vinegar, phosphoric, muriatic all work. Different levels of time, mess, expense. There are some good ideas for how to make a dip tank in the comments. Sandblasting also works.
Ceramic is what you want.
It worked great until the scale got really thick - then only OK. It did work though.
@@ThrottleStopGarage I thought you were using zirconia rather than ceramic? Ceramic will handle the heat a lot better than zirconia.
@@plsreleasethekraken The Walter Abrasive sanding disks were ceramic. If I had to strip the mill scale off the thick plate, I'd hit it with my torch first then the sanding disk.
@@ThrottleStopGarage gotcha, makes sense.
@@ThrottleStopGarage Try the Pferd Combiclick ceramic discs (red). They won't last as long as the Flexcuts, but are half the price; they won't gouge as badly either. Not sure if they are cheaper than the Walter ceramics you got though.
Bit of an odd choice not to try fibre discs... The cheapest and probably most effective.
I was going what what was suggested at the welding store. I'd try a coarse disk if I didn't have to buy a box of 25! Any suggestions on brand?
@@ThrottleStopGarage 3M, Dronco, Klingspor, Pferd, Norton, Abracs are just a few reputable names off the top of my head.
The best abrasive material is ceramic, followed by zirconia, and then boggo aluminium oxide.
Naturally, the ceramic abrasives cost more, but perform better and last longer. 3M cubitron (ceramic) is very highly regarded, but not cheap.
Aluminium oxide costs the least, but doesn't perform as well or last as long as ceramic.
Zirconia is in the middle.
Get a rigid backing plate. This will prevent the disc from following the contours and hitting only the edges. A backing plate which is vented is a wise choice as it lessens the effect of heat on it. You could also try a rubber backing plate to compare the difference between the two.
Check eBay as you should be able to pick up single discs or in multiples of 5. It's generally a good place to find deals on everything and anything.
@@goldar4846 Working on this now. Thanks.
@@goldar4846 picked up some ceramic 36 grit disks. They work great. About the same as the mill scale disk.
@@ThrottleStopGarage I'd be keen to see the result of a rigid backing pad vs a rubber one.
Best discs for removing mill scale in my opinion are the discs that contain Silicon Carbide like the discs from 3M( Scotch-Brite Clean and Strip XT Pro Disc with Extra Coarse Silicon Carbide)
Tried those in the video. Worked great on light mill scale.
I would skip all the fancy discs and go straight to the sanding disc w/ backer pad for removing mill scale in all cases! It is in fact what the pros use. It cuts through the scale on the first pass as well as it cleans up the mess made by the "mill scale" disc.
Another viewer commented this as well - I tried it and can't believe that the welding store guys didn't tell me about this! They worked great.
I heard that coca cola would work really well and there are some videos on YT which proof that but never tryed myself.
Destilled vinegar shold also work
Yes - phosphoric acid will work.
Before I watch the video: I now own an Amazon Wagon :-D 67, cream, very very sweet, dream come true for me.
Nice! I've looked but they're not very common here and I now have a 245 for "wagon" duties.
@@ThrottleStopGarage They're not common anywhere - they had a shorter production run and make up about 1 in 7 Amazons with 3 in 7 being Sedans and 3 in 7 being coupes, globally. In my country there is only 4 or 5 Amazon wagons, so you pay what they ask, and I was lucky the asking was about the same as a clean 240 wagon sells for here, now. Score! :-D Also have a couple of 245s, 965, used to have a 945 and a 745 in the US years ago, plus 740 sedan, 2x 240 sedans, and a 360 5 door and about 10 other cars that aren't Volvos, ha ha. Is your 245 a 245 as per badge? or a later 240 wagon? :-)
@@fredio54 In western Canada, very few wagons remain! All kinds of 2 and 4 doors. My 245 is a 1984 it's a little rough but works well. I've also got a 242 that I race. Its mechanically great - body is getting rusty again. More projects for later on.
@@ThrottleStopGarage Yeah, I can't back this up, but I'm 74% sure that wagons have a higher attrition rate due to their practical nature:
Do more towing
More gear loaded in the back
Driven more distance
More time in the rain earning their keep
More chance of being crashed due to all of the above
So if Amazon wagons started off being 1/7th then they're probably more like 5% now or there abouts. 84 was probably still 245 on the back, I can't recall the year of my earliest, but it's a manual GLT wagon in maroon that was near free and has some rust in lower parts due to grass storage for years. It has the long nose bonnet like the 262C has and the smaller plastic mirrors between the modern style ones on the later cars and the chrome round ones on the early cars. 7 seat option, too. I think that is the engine with the hot factory cam? Not much of a single cam guy, though... :-) have 4 16v engines, 3 in cars, one in bits, all to join forces with a B230F and go into service long term. Have you done a tour of your 242 or 245 on your channel? If so I'll search for them. If not, please do! Just a walk around, explanation/description/short drive maybe?
I thought that was Al Bundy for a couple of seconds 😁
He wishes. LOL.
@@ThrottleStopGarage me too. Peggy Bundy is a FOX!
Sorry but the best way is to use White Distilled Vinegar now a soak over night will clean it great with zero deterioration to the Metal, if time is an issue then there is 30% or even 45% white Vinegar which will bring the soak time under three hours. And last but not least is electrolysis with Vinegar with Salt added to water but any of these methods would leave the Metal without scratching the material.
Yes - I've used that technique before. But when you don't have access to a vinegar bath due to time or the size of the parts, then it's abrasives to the rescue!
@@ThrottleStopGarage I have trays for the size of the part you made but not much larger for that I would go with Electrolysis. For long pieces I use PVC pipes as my tubes. But I agree sometimes there just is no replacing abrasives especially when removing zinc plating. thanks for the reply.