Best way to remove black oxide skin from hot roll

[nickel-city-fab]

Yeah weld prep, OK.

Yes, the scale dulls the angle flap disks in short order. Maybe cubitron ones would last, that stuff eats everything. Have not seen them, but they must exist.

The SAIT link had these new ceramic ones, would that be cubitron? I have heard they exist but have not used them.

[JRouche]

Ive got some pieces of hot roll A36 that I will be using on a project, what would be the best way to remove the black oxide skin prior to machining? Or is it even worth worrying about. I have never worked with hot roll before, but have heard that the outer skin is tough on HSS end mills, however I don't know this from personal experience.

I use these three abrasives for mill scale. The PFERD is great if you have a powerful grinder. I use them in my 9" mil, they should have them in 4-1/2".

The CGW 4-1/2" disc in 40 grit will eat everything, including skin and clothes.

The lil cutoff wheel is good for tight spaces (on edge only).

That Hilti flaring cup is what I used on my thick welding table. Again, needs the power but will knock down scale on a flat surface easily. JR

[nickel-city-fab]

When I have slag and scale, I just use the 1/4" thick type 27 grinding wheels on whatever size angle grinder is available. If I'm worried about the finish after that, I follow up with a flap wheel. 98% of the time it isn't necessary for what I'm doing nowadays, though

[J Tiers]

The SAIT link had these new ceramic ones, would that be cubitron? I have heard they exist but have not used them.

Probably similar, I looked up what the cubitron is, but do not recall the details. I know they eat steel, even with a wimpy grinder

[dian]

after several hours simering in 15% muriatic. then 4 hours simering in 5% vigegar/salt solution. no tig on that. now, afrer two days there is plenty of rust.

[Fasttrack]

I treat mill scale the same as the surface of a sand casting. Whenever possible make the first cut deep enough to get completely under the scale. I've found the greatest tool wear comes from a light pass with the tool coming into and out of contact with an irregular surface. As long as the tip of the tool is under that scale just plow away. Normally I'm using HSS too, as I'm just taking the top layer off, even if there is some tool wear it's just a quick touch up on the grinder and then back to cutting. Quick and easy to touch up HSS.

That's been my experience as well. I think the small amount of deformation as the chip is formed is enough to break and flake the scale off ahead of the cutting edge, anyway.

[Ironbearmarine]

Unless you are under industrial or commercial requirements to descale, it seems to come down to how much fun you want to have preprocessing your A36 stock. Personally, for machining projects i will just cut away the scale rather than abrade it, for fabricated small projects, abrading is easy. For larger projects that will get painted or powder coated i prefer having it sandblasted. If i have lots of small components i pickle them in a vinegar and salt bath aided with a 12 volt power supply. My 2 cents.

[MetalByter]

This was given to me by a friend, it is fantastic to remove the scale and very fast. Leaves a finnish like sand blasting.

[Illinoyance]

...and you should take extra care not to get it twisted; I hate it when I get my Swartz twisted!

That is Schwanz you don't want twicted.......or stepped on