Andrew Colglazier

2 minutes ago, jmccustomknives said:

Have you done this test then?  Some are made from 4140 then case hardened.  This steel will harden but will not snap clean or easily like high carbon steels.  As a rule I don't mess with rasps too often.  I've been burnt (figuratively) by name brands that were case hardened 4140.

I haven't,  but I will now.  I appreciate the tip.  It will no doubt save me time in the future.  Thank you! 

19 minutes ago, jmccustomknives said:

Heat the tang of the rasp like you would the whole thing and quench it in water (just the tang).  From there, do not temper but put it in a vice with the hardened tang sticking out.  Give it a tap with a hammer.  If it doesn't break but bends you've got a case hardened steel.  If it bends but is very tough then it's likely 4140 or something similar.  Either of those outcomes put those rasp in the art department and not for knives.

Oh, wear your safety gear.  Don't want to loose an eye to flying metal.

 

While I shy away from rasp I did have a good experience with a Heller.

Yes sir.  Hardening isn't the problem.   They harden in brine, but warping is a problem.  If I quench in oil, they don't warp, but don't seem to harden either.

5 hours ago, ThomasPowers said:

Well you have covered most of the items I check when things start warping on me---any difference in brand of rasps?

Yes, could be the problem.   These are Safecut and no name.  I usually use Heller.  

I will move this to the knife section, since you didnt notice it

1 minute ago, ThomasPowers said:

How hot are they getting during grinding?

I grind bare handed.  If they get too hot to touch, I dip in water.

On 11/5/2013 at 9:05 AM, BCROB said:

 

When I quench in oil mine won't harden, but they will in brine.

26 minutes ago, BIGGUNDOCTOR said:

What is you actual process? How do you anneal, normalize, etc...?

Anneal - heat to non-magnetic, bury in hot go get ashes and allow to cool overnight.

Grind with belt grinder. 

Normalize - heat to non-magnetic and let air cool 3x. 

Quench - heat to non-magnetic, quench in brine (or oil).  If oil, the oil is warmed to +- 130.

Temper - place in convection oven for 1 hour at 450. Allow to cool to the touch, repeat 3x.

The blade will warp but harden in brine, won't warp or harden (file test) in oil.

30 minutes ago, ThomasPowers said:

Are you going thinner on the blades doing them stock removal before heat treat than you were forging them?

Actually the forged blades are somewhat thinner than stock removal. 

Good questions  -

I don't know if I'm overheating.   I'm going by color and demagnetization. 

I've been using brine with forged blades, with a small amount of warping, but these blades seem to be more prone to warping (stock removal)

Annealing - grinding - normalizing x 3 - quench.

I'm making knives.  They have been large single edge blades.

The rasps I have harden in brine, but warp, even when normalized.

They do not seem to harden (or warp) in oil.

What to do?

Does stock removal vs forging make a difference in how rasps behave when quenching? 

Any help welcome!