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

Joined
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?
 

3fifty7

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Dec 24, 2016
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I’ll let the heat treaters give an official answer but Id remove all surface treatments and grind to about 120 grit.
 
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Apr 24, 2013
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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.
 
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May 1, 2019
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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.
 

Stacy E. Apelt - Bladesmith

ilmarinen - MODERATOR
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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.
 
Joined
Mar 10, 2013
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346
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.
 

Taz

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Apr 28, 1999
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1,201
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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