Finish prior to heat treat?

Forrest Taylor

Forrest Taylor

Knifemaker / Craftsman / Service Provider
Joined
May 13, 2021
Messages
354
To what degree of finish is the general rule prior to heat treat.
Is there a certain grit most go to with finer grits done afterward?
Just looking for some basic guidelines.
 
The higher you go the less you'll have to sand on hardened steel... That being said going above 400 or so and you start getting less benefit.
 
I only go up to 120 grit pre-heat treat. I need to thin the edge down after heat treating, anything higher than 120 grit generates too much heat and takes too long to thin down the edge. So if I have to go to 120 grit post-heat treat, doesn't' make much sense to spend the time grinding above 120 grit pre-heat treat.
 
I leave some grinding for post HT, typically taking the edge to about 0.04" prior.
So I use 36 and 60 grit, then a couple quick passes at 120 to avoid the possibility of stress from deep scratches.
 
barlowchiro said:
I only go up to 120 grit pre-heat treat. I need to thin the edge down after heat treating, anything higher than 120 grit generates too much heat and takes too long to thin down the edge. So if I have to go to 120 grit post-heat treat, doesn't' make much sense to spend the time grinding above 120 grit pre-heat treat.
Click to expand...
 
Thanks for the replies. I guess it depends on how much post heat treat grinding I plan on doing.
 
I think you got the answer there depends on how much post heat treat grinding you'll do but I don't take anything thin enough pre heat treat that I wouldn't start with a 120 so that's what I grind to pre heat treat. Never had issues with 120 scratches causing a crack in quench but I have had a crack on a 60 grit finish so I no longer do that.
 
I was just looking at this issue. I was going to send in some knives with a 120 finish but now I am leaning towards 220. I see a lot of people stating 220.
 
Depends on the steel. If it is a very hard steel to grind post heat treat then I will go to 220 and have the blade about totally ground and hope there is no warp post heat treat.

CPM 154 and AEB-L I will grind totally post heat treatment.

Most high carbon steels I will grind 75% done to 120 grit and then finish post heat treat.

I do not hand sand until I get the blade ground up to 800 cork with green compound then cork polishing belt with green compound to almost mirror finish. I let the machine do the hard work, Then hand sanding is a breeze
 
AVigil said:
Depends on the steel. If it is a very hard steel to grind post heat treat then I will go to 220 and have the blade about totally ground and hope there is no warp post heat treat.

CPM 154 and AEB-L I will grind totally post heat treatment.

Most high carbon steels I will grind 75% done to 120 grit and then finish post heat treat.

I do not hand sand until I get the blade ground up to 800 cork with green compound then cork polishing belt with green compound to almost mirror finish. I let the machine do the hard work, Then hand sanding is a breeze
Click to expand...
I want to buy a cork belt, what speed are you operating at 800? I have been grinding to 220 or 400 on grinder and start hand sanding. Hopefully cork will speed up my hand sanding task.
To answer OP question, I usually grind to 220 before heat treat, AEB-L and 1084 (only steels I have used). I usually start with 120 on 1084 after heat treat regardless, the edge will be thicker and need to be ground down.
 
scherf68 said:
I want to buy a cork belt, what speed are you operating at 800? I have been grinding to 220 or 400 on grinder and start hand sanding. Hopefully cork will speed up my hand sanding task.
To answer OP question, I usually grind to 220 before heat treat, AEB-L and 1084 (only steels I have used). I usually start with 120 on 1084 after heat treat regardless, the edge will be thicker and need to be ground down.
Click to expand...
What speed? The speed between not super fast and not super low.
My progression is 50 grit, 120,220,400, 400 cork no compound, 400 cork green compound, 800 cork green compound, Cork polish belt green compound.

600 grit hand sand.
 
You must log in or register to reply here.
Back
Top