Sharpen then harden or the other way around?

G

gasrc

Joined
Feb 25, 2008
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I'm not knife maker. I have to design a blade at my job. There is a one-piece (welded) cutting tool that they've been using 316 to make...blade and all. Of course, 316 is not an ideal blade steel. The tool has to be highly corrosion resistant and available in round bar as well. The thought is to replace the 316 with 17-4 and harden it to condition 900 (40-47Rc). There is also another cutting tool that I'm designing with separate S30V blades.

So the questions:
1) Do you sharpen the blades completely before heat treat hardening or just cut the blade profile, harden, then sharpen?

2) Can S30V, after being hardened, be sharpened with a fine grit sanding belt? I know that sounds blastphemous to a true blade craftsman, but that is mostly likely how it will be done once the tool reaches the customer.

Thank you
 
I'm not a knifemaker... yet.

That being said, I'd get most of the grinding/sharpening work on the edge done before the heat treat, and then touch it up afterwards. The user of the item is going to have to sharpen it after heat treating anyway.
 
With S30V you better sharpen before HT ! Sharpening for the customer is best with a diamond sharpener.
If you told us more about environment and what you were cutting we could give better advice.
 
if you take the edge too thin before ht the edge can develop cracks. i leave at least a 1/32" flat to help lessen the chances of this happening.
 
Not only will grinding the edge too thin cause warpage and cracking problems, you dont want to be constantly worried about cutting yourself, handling a sharpened blade while trying to do your other knifemaking and sheath making operations.

Final edge sharpening should be the very last step.
 
Mete, Just curious? Why would it be better with S30V to sharpen before heat treat? I'm not familiar with that alloy. Also, why do you recommend a diamond hone for final sharpening?

Just curious?
 
The big problem with sharpening S30V is that it contains 4 % vanadium. The vanadium carbides are VERY wear resistant. That makes for a very wear resistant edge and a great blade .I carry a Sebenza with S30V so I'm very familar with it .Recently I've been playing with Fallkniven's 3G which is a similar supersteel. Normal sharpening is done with diamond and perhaps ceramic. Makers find that in the hardened condition polishing a blade is very difficult so you don't see many with a high polish.For the maker then grinding down very close to final dimensions before HT saves a lot of work and grinding belts ! As an air hardening steel and plate quenched you don't have to worry about cracking or warping.
Just another example of knowing and treating each type of steel as an individual !!
 
O.K. Mete thanks.

Air hardening steels sure are great for going thin... :)
 
mete said:
Makers find that in the hardened condition polishing a blade is very difficult so you don't see many with a high polish.
Click to expand...

Not difficult, just impossible.:D


I use ceramic belts on S30V after heat treat... it ignores everything else.
 
gasrc said:
I'm not knife maker. I have to design a blade at my job. There is a one-piece (welded) cutting tool that they've been using 316 to make...blade and all. Of course, 316 is not an ideal blade steel. The tool has to be highly corrosion resistant and available in round bar as well. The thought is to replace the 316 with 17-4 and harden it to condition 900 (40-47Rc). There is also another cutting tool that I'm designing with separate S30V blades.

So the questions:
1) Do you sharpen the blades completely before heat treat hardening or just cut the blade profile, harden, then sharpen?

2) Can S30V, after being hardened, be sharpened with a fine grit sanding belt? I know that sounds blastphemous to a true blade craftsman, but that is mostly likely how it will be done once the tool reaches the customer.

Thank you
Click to expand...

316 stainless for a cutting tool ? Being an austenitic stainless 316 isn't appropriate for a cutting tool of any type (imho). Are you sure you don't mean 416 stainless,(still, imho, not the best choice) ? 17-4, a precipitation hardening stainless, is better than 316 but still, (imho) not the best choice for making a cutting tool.
S30V makes a very fine knife and can certainly be sharpened after hardening & tempering.

What are you cutting ?

fwiw, I sharpen all of my knives using fine grit sanding belts (3M micron belts) on my KMG, set-up with my roller platen.
 
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