How can I remove gray discoloration after HT?

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psycho78

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Jun 17, 2006
Messages
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I sent my first two blades off to Texas Knifemakers Supply for HT and cryo awhile back. Both ATS-34.

When I got them back, they were grey and discolored. A scotchbrite belt wouldn't get that stuff off, it just kind of polished it.

I was told to finish my blades to whatever degree I wanted ( I like a nice very fine scotchbrite), and it would just "buff" right off. Looks like the gray scale stuff is tougher than I thought.

I am so paranoid about ruining HT on the grinder. I'm a new maker, and sticking that nice blade back onto a belt and possibly screwing up grind lines etc, isn't my idea of fun.

Is there a gentler way I can get this grey stuff off? and possibly just run it back over the scotchbrite belt for the finish I had before sending it in?
 
Hand-sand it off with fine grit paper and the lube of your choice. (Mobil1, water, wyndex etc) Then you can touch it up with your scothbrite belt or whatever you like.
 
try what james said which will work but i have a question. is your scotchbrite belt in good shape and cutting good on another piece of steel or is it loaded up?
 
I want to avoid hand sanding if all possible. I hate it, and I'm not good at it whatsoever...lol

The scotchbrite is brand new. it's an extra fine, so it's probably not rough enough to cut it.
 
A bit of scale will be on any heat treated knife and should be fully removed to get to hard steel.

I don't know of any other options rather than hand sand and machine sand. If you do have to machine sand, then go quick. Don't let the steel sit in one place or it will heat up. Move quick especially around the edge and tip. Also make sure you use ungloved hands and dunk in water any time it gets too hot to hold. I dunk a HT'd blade every/every other pass.
 
Hydrochloric acid. Soak it in 5 minute increments, until the scale is gone.
 
Don't store HCl in your shop. Don't store HCl in your shop. Don't store HCl in your shop.

Pretty much standard practice to go one grit backwards after heat treating, or at least back to the grit that you stopped at. With an air hardening steel, I think you'll find that a fresh belt of the grit you stopped at, or a quick hand sand will take it off. It's not going to be thick.

Oh yeah, -don't- -store- -HCl- -in- -your- -shop-.
 
I'm with Dan; I would add three days in a vinegar soak and any scale will fall of the blade surface. I put every thing I forge through this soak cycle. After it comes out of the vinegar use soap and water, then 0000 steel wool with W-40.

Fred
 
I agree-don't store HCL in your shop. It will rust everything, unless the container is tightly sealed and very clean.
But- it does wonders on steel.
 
Thanks guys! I will try the vinegar trick. I'm gonna see about a coarser scotchbrite. i am a sucker for the belt finish.
 
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