Mill Scale removal

[Sundown]

I have finished putting the new weld table togeather and just need to get the top surface done. The 30" X 40" X 1/2" plate I have is HRS and has some very heavy mill scale on it. I cleaned the bottom with a grinding wheel, then flap disk, and finally some Sait sanding disks. I tried my belt sander with not very good results. My question is, is there a better way to get the mill scale off the top surface than the way I did the other side? and if I have to do it the same way, what can be done to dull the finish so I have fewer reflective problems?

[Laiky]

I can't tell you how much i hate Mill scale! The last load of tubing i bought for my welding rack was hrs. I waste more time grinding and cleaning up than i do fabricating. If you can sand blast it, i would think thats the best way but most people aren't set up to blast much less a big table. I would suggest a very aggressive flap wheel (i recently bought some 24 grit to speed clean up of the remaining steel) but haven't tried that yet. If not a flap wheel then a depressed center grinding wheel, the ones that angle back so they are flat when the tail end of the grinder is sticking up. Any other ideas, i'de like to know.

[Sundown]

I did get a 24 grit angled flap disk made by Norton and it works fairly well, I havn't seen any angled grinding wheels so I will have a look and see if I can find one. I think I am stuck with the way I did the bottom, then do an extra step and block it with 240 wet/dry to get rid of the shiny surface.

[Pile Buck]

Hi George, depending on the thickness of the mill scale, but have you thought about one of the bigger cup brushes on a 7-inch angle grinder. Those braided / knotted cup brushes you can almost stand on the back of the grinder they’re so tough.


Went and found a picture fur ya

[hankj]

Hey, George, Carl's right on it, as usual. I just got a 3" knotted wire cup brush with 5/8 - 11 threads and screwed it on the Milwaukee 4.5" angle grinder. It's all I'm using from now on! Little hard to control on edges sometime, but it blows away scale really nice, and leaves the steel pretty much alone.

Hank

[Bob Sigmon]

I totally agree on the wire cup. Those babies really eat up scale and on large items like plate for a welding table they are perfect. I like my wire wheel stand for smaller pieces but the wire cup should make short work of the scale and leave a pretty nice finish for your top.

[precisionworks]

George -

If you lived closer, you could use my 3HP horizontal shaft grinder with a 6" flap wheel.

If you have any large factories nearby, they might do the top for you at little cost with a similar air grinder. Otherwise, the cup brush that Carl suggested, powered by a 15A angle grinder, will get it off.

[fatfrank]

7" flap disc on a 15amp grinder will take that stuff off in a heart beat, wear some good fitting eye protection, it will throw grit everywhere.

[Pile Buck]

When I worked in the shop back in the late 70’s early 80’s we got a contract to laminate 4-inch thick plates. These plates must have had a good 1/16 to 5/64-inch thick mill scale on them . We were only allowed to remove the mill scale in the weld zone, nowhere else ! Well thank God. It was slower than **** to try and grind that crap off. What we found that worked best, was the large air powered needle guns. I never seen mill scale like that before or since.

[Scott V]

Try Acid!!!

[precisionworks]

What we found that worked best, was the large air powered needle guns.

Good call! An Ingersoll 182, CP9356, Patco P1-B or Cleco B1 would make quick work of that scale. For an inline, hand held tool that weighs five pounds, the power is incredible.

[fun4now]

i use a noted wire cup on my 4.5" grinder all the time with real nice results, gives you a satin type finish that wont cause too much glare. sertinaly far less than a flap disk finish, although you could flap disk it first then wire cup it to take the glare off.

never tryed a needle gun but have been considering getting one for quite a wile now, mostly for the slag after plasma cutting, and or flux core wire. if ya get 1 lets us know how it workd. i know you can get the needle atachment for a standerd air hammer, that might be a cheeper way of trying it than going for a prefab needle gun but the results may very between the atached version and the dedicated needle gun.

[Sundown]

Thanks for the ideas guys, I do have a SS twisted wire cup and will put it on the DW831 to give it a try. Right now I have the top setting outside with Phosphoric Prep & Etch to get rid of some minor rust before attacking the mill scale. I do have a compressor and could get a HF needle scaler (no since getting a expensive one no more than I would use it) to try if the cup brush doesn't work.

Scott,

What kind of acid were you thinking of?

[Coalsmoke]

myself, never have bothered removing the mill scale for welding table tops. It adds a bit of protection against rust and I haven't had problems with conductivity. So, I gotta ask, why make more work for oneself

[joebass]

I also say, why bother? You be grinding tacks and spatter off any way. Why would you ruin an expensive stainless brush on mild steel?