Why grind before heat treating?

[Leon Husock]

Aside from things like applying clay to a blade where it's important the steel be clean first, is there any particular reason to grind before you quench (assuming you've forged as close to finished shape and thickness as you can)?

Generally I'll profile a blade and file the shoulders in, but I won't take off any thickness pre-quench. I figure the thinner it is the more likely to warp, and I'll take reduced likelihood of warpage over the little bit of extra speed and reduced wear on my belts I get from grinding steel when it's not hardened. But I feel like I must be missing something here.

 

[Stacy E. Apelt - Bladesmith]

I would grind it clean of all hammer marks and leave it at 120 grit. It is a lot harder to get those deep dings out once hardened.

 

[Leon Husock]

I would grind it clean of all hammer marks and leave it at 120 grit. It is a lot harder to get those deep dings out once hardened.

Usually I give the spine a quick tap on the press with the big flat dies and then I grind enough material away in the bevel that any hammer marks that are left eventually get ground out (though occasionally I do forge the point too thin and I can't take enough material away to completely remove the marks, but grinding before heat treat wouldn't fix that anyway).

 

[Daniel Fairly Knives]

water hardening - grind most of the way
oil hardening - only grind thicker knives
air hardening - almost never grind besides some metal removal/low grind on 3V and the likes because it is so hard on belts post ht

I currently make thinner knives in mainly Nitro-V so no pre grinding.

 

[Stacy E. Apelt - Bladesmith]

I think his question is about grinding a forged blade before HT.