Finishing question - Post heat treat

Brock Cutlery

Brock Cutlery

Joined
Jan 10, 2015
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I just wanted to ask how many take their blades back to the grinder after heat treat?
And if you do, what belt progressions do you use, and belt speed?

I've got my second knife on the sanding bench, and it's got a bit of a divit in the middle of the blade, about 1.5 inches. Very shallow. I'm not sure if it was my grinding, or something from heat treating. I took this blade pretty thin before HT. It's 440C

Thanks
 
Most everyone grinds post ht. On thin knives I only grind post ht. Keep dipping it in water to keep it cool. Take it up to whatever grit you want to finish with. The higher the grit, the easier it is to overheat it.
 
Most makers of thin blades with very fine edges like chef's knives almost always finish grind after heat treat.

In your case, since you want to remove a low spot that you've discovered after heat treatment, then there should be no issue in doing so unless you make the blade too thin in process. As mentioned keep the heat low, use new (sharp belts), and use the finest grit of a belt that will get the job done. You'll have to experiment yourself with this on this particular blade. The divot is probably as far from the bevel as your grinding belts are in width? This is a common occurrence.

Very diligent hand sanding before heat treat can eliminate the need to go back and regrind/finish hardened blades.

Since I make mostly hunters or blades with thicker sections, I completely hand finish my blades before heat treat and only touch them with abrasive paper after heat treating to remove discoloration from the heat treat process. I've found this to be a much more efficient method than trying to repair scratches or low spots in hard steel. I use air hardening stainless, which makes this possible.
 
I can appreciate both perspectives. I think I just took this too thin pre-HT. I think it warped. It's almost paper thin at the edge. It's a lesson learned.
On the fillet knife I made, I took it to a more reasonable thickness on the grinder and did all the sanding up to 400 pre-HT. After I just had to clean it up and smooth it out.
I think this one is just not going to be a good blade. Lesson learned on taking the grind too far.
Thanks for the comments.
 
Many good knives were too thin . . . if it is too thin at the edge, then reshape the blade to thicken it to the best of your ability. It may end up being a throw-away or you may end up with something that you really like.
 
I use a lot of 440c and I take the edge to .025" before ht. At that thick you will have to grind after ht if you want a good slicer. I take the final edge to .010" or so.
 
I might try and reshape it. It will lose it's shape, which I like as it is. But it might be worth saving. It will probably go in the hopeful pile for now though.
It seems knife making will let you know if you are a perfectionist. I never thought that about myself until now.
 
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