How clean does a blade need to be before heat treating?

eric brinkerhoff

eric brinkerhoff

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Mar 10, 2013
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I have some blades in 52100 that I played around with etching and cold blue to give myself a"preview" of how they might look. I plan on sending them out for heat treating. Is it absolutely necessary to clean all of the black and blue from these blades?
 
I’ll let the heat treaters give an official answer but Id remove all surface treatments and grind to about 120 grit.
 
The cleaner it is prior to HT, the better. Clean off all oil residue & blueing with acetone, de-burr all holes & edges. I typically take blades up to 220 or 320 for stainless grit and leave very little for removal & cleanup after they come back. I've run them pretty thin and still have good luck when they're heat treated, a dime is too thick at the edge for my stuff, but YMMV.
 
so far i have not found it matters, other than deep sharp scratches that could act as stress raisers.
if you're sending it to someone else it's probably a good idea to clean them, just so you're not putting gunk into other people's kilns. seems polite more than anything else.
 
As long as sharp edges and deep scratches are removed, the bluing won't matter.

Just a comment, but etching/bluing the steel unhardened will not give the same look as etching/bluing hardened steel. Also, hardened steel must be fully sanded down to remove all traces of decarb or there will be splotched on the etched/blued blade.
 
Thanks everyone! I normally get my knives to about 1000 grit or so ,go very thin at the edge,and I design my knives without stress risers( except for cold stamping and jimping, those probably cause a little stress) I was mainly wondering if I had to go out there and buff all those blades again or if I can just stuff them in a flat rate box and send them off.
 
When I asked Jarod Todd, he said leave them in mill scale, no sharp edges or deep scratches. I cleaned up the profiles to 220 grit (broke the edges with 220 as well), left the mill scale (some had already been ground a bit, so cleaned those up to 220), drilled and chamfered the drill holes and sent them. I did use denatured alcohol to wipe off/clean all of the blades as I packed them. 32 blades went out :)
 
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