How fine to sand before h.t.

[redsquid2]

I have been sanding up to 400 for the past several years. Then h.t. Then go down to 320, then back up again, with no grinding after h.t.; only hand sanding after h.t.

Now I want to try grinding after h.t. Probably I will start with a 120 grit belt after h.t., to make the bevels a bit thinner, then just hand sand from there. Does this sound reasonable—with a 2X42 grinder and 80CrV2 at 60HRC?

 

[Josh Rider]

That’s what I usually do for oil quenched simple steels. For stainless or air hardened I take them closer to finish before heat treat.

 

[navman]

for me it depends on the alloy. For S110V I take it to 3000 grit, with the intention of backing it off to 6-800 grit post HT. For AEBL I rough grind to 60 grit only, then finish grinding and hand sanding post HT.

with 80CRV2, I have rough ground to 60, leaving a good percent of steel, the finished post HT.

 

[Stacy E. Apelt - Bladesmith]

I agree with Navman, on the hard high alloy steels, take it as high as you will go in the final finish. On simple carbon steels, that you will grind after HT, 120 grit is fine, but I usually go to 220 or 400 anyway … to be sure there isn't a deep scratch or something that will cause trouble later.

There is a reason you don't want to HT a blade with coarse grind lines on it - stress risers. Stress can propagate along a deep coarse line and break a blade in hardening, or in straightening. Above 100 grit this diminishes to being not a real issue.