Welding Tips and Tricks

https://www.amazon.com/BHA-Silicon-Carb ... PRWP&psc=1

I know Oscar has had great success with some semi flap disc type silicon carbide discs I'm debating ordering a couple just to try out, however I'm also wondering if anyone had given these a go.

Honestly, since I don't weld nearly as much heavy scaly steel as I used to and 3M 982C discs are shockingly decent at removing it yet not going dull practically the moment it touches it like flap discs do, but I may still order some of both.

I think I have something similar at work but they are a little 3 inch disc that has their own reusable Arbor with a rubber backing pad. It has a quarter inch shaft that you can either use in a die grinder or Chuck in a drill. I've never used them because I just can't stand air tools. That and I have other options.

There's one thing I have considered doing recently and that was cutting holes in both sides of my blast cabinet and then making rubber diaphragms that were cut out so that I could put pieces of Steel angle through the blast cabinet but still be more or less sealed at both ends. And that way I could do longer pieces of Steel angle. That's about the only thing I really have a lot of Mill scale to remove from. I've also thought about trying vinegar and muriatic acid but never seem to get around to it.

Let us know how you make out with them. Even if all they do is break up the heavy stuff and you still have to go back over it with a flap disc I'm fine with that. The last time I had a lot of the stuff to do I took it to my powder coater and had him sandblast a whole truckload for me at one time. He didn't blast it super clean but I didn't ask him to either. He got the worst of it and I get the last little bit. Next time I'll have him clean it till it's white.

I still use the ones I got from Empire Abrasives, but I've switched to the fine grit 120 and I like those better. Plenty aggressive enough and last way longer than the coarse grit ones that tend to disintegrate quickly if you hit an edge.

Oscar wrote: ↑Sun Dec 19, 2021 12:02 am I still use the ones I got from Empire Abrasives, but I've switched to the fine grit 120 and I like those better. Plenty aggressive enough and last way longer than the coarse grit ones that tend to disintegrate quickly if you hit an edge.

Silicon Carbide does like to bite into bare steel pretty aggressively if you let it doesn't it? At least that seems to be the brief memory I seem to have of trying a "masonry" silicon carbide grinding disc on steel. I generally don't like to leave a piece full of uneven grinding marks like using a hard rock inevitable does so a grit level that'll fairly quickly and efficiently strip the scale but without immediately chewing through the steel underneath faster than I can manage.

I used to work up through 8000 grit silicon carbide sandpaper after diamond stone work on extremely exotic steels like S110V because Aluminum Oxide abrasives were actually slightly softer than the vanadium carbides the steel was full of. So I was surprised to see that on power tools they seem to be a stone only abrasive other than situations like here. Basically when you're saying plenty aggressive are you talking on lighter surface finish type scale such as on 1/8" tubing, or do you mean aggressive enough to deal with even thick scale buildup on thick plate steel? I had some 2'x3' 3/8 steel plates cut from the center of I beam pieces that had scaling so thick that an HCL acid bath wasn't a quick way to strip it clean, it just the first step of etching into it enough that a sandblaster, nonwoven stripping disc, or other method might actually make remotely acceptable progress in stripping the rest of the way. If I ever see scale like that again, I'm just leaving it at the scrap yard, but I'm curious you find these useful for things like thinner plate and tubing , or if these things are the level of aggressive suited for use on scaled up steel plate and such.

Have you tried the 7" discs or only 4.5?


Oh, on a related note, do you have a suggestion what grit of cubitron 982Cs to get if I order a 25 pack? the welding store I got mine at only had 60 grit which were still remarkably fast, especially since thankfully I've not really had any grinding necessitating heavy material removal like I have in the past, so maybe 60s are a good balance, but if 36 grits are significantly faster still and don't tear themselves apart too fast to appreciate the faster cut speed then when I do run into a task where I need to bear down and take off a whole lot of material I know I'm going to want the most aggressive fastest cutting discs I can get my hands on thats when I'm going to be burning through discs enough to actually be glad to have 25 anyway. so I'm not sure, aggressive sounds better for when I really need them but if they don't cut all that much faster but just leave an absolute awful mess of a surface behind, I could see maybe 60s. I'm sure you can tell me how the 36s do in comparison.

The 36 grit 3M fiber discs are very aggressive, but I've noticed that the edge loses the ceramic faster than I'd like. Not the sharpness of the ceramic, the ceramic bits themselves. I think it's because the edge flexes more and the resin that holds the ceramic tends to crack and then it lets loose the ceramic media. And those [ceramic media on the edge] are the ones that do the most damage since it's easier to hit the part with the edge. The 60 grit seems like it would be a good compromise.

generally a shop won't let you do this for millscale, just no time for it... but for my own side jobs at home, if I can't get my hands on cold rolled sheet and I'm forced to buy hot roll (re: mill scale sheets), I soak them in vinegar for 24 hours first. Any supermarket sells cheap vinegar by the gallon, it takes about 2 gallons to completely submerge the sheets. I use a big oil drip tray that you can pick up from the auto parts store real cheap, they can hold a pretty large sheet. Don't try it indoors unless it's in say a detached garage, that much vinegar fumes can be overwhelming. I do it outside under my front stairs of my house (it's my garbage area, and don't have to worry about wildlife getting in it and get poisoned as they won't get close to it, it smells really strong). Just let it soak overnight, a good 24 hours but sometimes in half the time depending on how thick the mill scale is. Then just wipe it off with a rag and voila', no more mill scale, no ruining expensive flap disks, no cursing, no elbow grease.... easy peasy, and it's cheap as hell. You could use hydrochloric acid too (re: muriatic acid), but that stuff is nasty, toxic, poisonous, and then what do you do with it after you're done with it... not exactly environmentally safe. Yeah, it works in half the time of vinegar, but vinegar is safer and cheaper. Try it out, you'll never waste another flap disk again.

On the note of acids, we've used muriatic acid to strip mill/weld scale on welded tank assemblies.

Works great at stripping scale etc, but the biggest conundrum we've run into is getting it neutralized before the rust starts.

We only do it that way when the tank will be ton dipped for corrosion/ease of soldering to the new core and there is sealed baffle sections etc. Otherwise just sandblasting is done since the collateral effects of blasting are easier to deal with than Acids.


And a sidenote about vinegar, I found a company online that does bulk cleaning/industrial vinegar up to 30% concentration. Would assume it would get your soaking time down drastically.

Pretty sure it was discount vinegar or bulk vinegar.com etc. Think all I did was google bulk vinegar for sale and it popped up.

Yup, I've played with acid extensively on home projects in an attempt to both be lazy and to avoid leaving gouge marks in everything, vinegar will work in a pinch when let sit for a good while especially on reasonably light scale, and mixing up a batch of fresh citric acid works quite well too in my experience however for some reason it seems like it needs to be mixed up relatively fresh or it looses effectiveness in subsequent days. Both work WAY faster when warm or somewhat hot solutions than at room temperature however that's not always an option and if you have additional suggestions as to more ways to keep a large container heated or warm for cheap I'd love to hear them.


I'm very curious to try 30%+ vinegar to see if it's noticably faster than household grade or not and would justify the price. I have use Oxalic acid a few times but I can't remember how well it worked on millscale, just that it took rust off faster than anything I'd ever seen, also it's poisonous as well.

HCL and sulfuric acid can both strip it off within moments depending on the concentration, and are used industrially sometimes for that very purpose, but they both, and especially HCL will contaminates and destroy everything nearby, the fumes flash rust any nearby steel, the stripped part itself will often rust over within seconds of pulling it from the acid bath if you don't dunk it in a neutralizing solution the moment you pull it out. And they'll destroy any clothes a drop happens to ever splash on to make things even more fun. So I just avoid it these days.

I'm curious about the 30% vinegar too, if you ever wind up trying it post about it here if you don't mind.

And yup HCL destroys things around it rather quickly, can bring a brand new set of pliers into the solder area where a bit of HCL is used and it just wrecks everything in at least a 6ft radius. Brand new pliers can look like they sat outside for 50 years rather quickly.

Works great but the collateral effects of using it are pretty high unfortunately.