Sanding "edges" pre HT.

M

mds

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Dec 17, 2014
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Hey everyone. Relative beginner here, still figuring out my process. I have a question that I probably should have asked a while ago about sanding edges pre-heat treatment. I wasn't able to find info anywhere and I've never actually seen anyone do any work to their edges/profiles pre-heat treatment. BTW, when I say edges, I mean all the way around the knife, not just the blade edge that we usually think of. Anyway...

I'm about to start sanding up a batch of 3/32" O1 knives that have been profiled and drilled. I'm going to do all my bevels after HT. I can hand sand til the cows come home but sanding those edges takes me forever as my Grizzly 2x72 won't take a small wheel. So I'm wondering, pre-heat treat, how deep is too deep when it comes to scratches? Can I just grind the profiles and then HT or do I need to keep going with the edge sanding? I don't mind the extra work but when I've got twenty or thirty knives to work on, that adds a lot of time/sandpaper and every bit of edge gets cleaned up after the handle is on anyway.

thanks everybody!
 
I'm no pro by any means but I want to chime in here, I do all the profile grinding pre heat treat. With carbons and 01 I go to 220 grit before heat treat and use the same belt to clean up my profiles after treat and work up from there to what finish I am looking for. I always go to 220 pre heat treat because the scratches from 220 are quicker to get out rather than the 60 or 80 grit I start with. Hopefully some with a lot more experience than me will guide you better here.
 
Craig, I do too. My confusion comes from having watched hundreds of hours of video and never seeing anyone clean up a single profile. Until this batch I've only made a few knives at a time and have been paranoid about breakage. I've hand sanded every single edge and curve of every knife I've made and I'm starting to think it isn't necessary. Thank you for the reply, by the way.
 
By sanding are you talking about grinding with your 2x72? Every single part of my knives get ground before and after heat treat. I either use the top or bottom wheel on my platen, the flat platen its self, or the slack belt. If you have a small contour and don't have a small wheel attachment just turn the blade 90 degrees and use the slack belt. Use a j flex belt and you can split it in half if needed. This is how I polish the tangs on my knives.
 
Matt R said:
By sanding are you talking about grinding with your 2x72?
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Sort of. I'm hoping to avoid the sanding and stick to the grinding. I know how to get into the small contours with a belt, I'm just not sure which grit is acceptable to stop at pre-HT. Ordinarily, I'll rough out my profiles with a 50 grit, and then go back and clean them up with something finer on the grinder, and then hand sand to make sure the scratches are out. But the chicken littles of the knife making community have lead me to believe that even the finest scratch, anywhere on the steel, will lead to stress risers causing the knife to explode while I'm handing it to a customer. So I hand sand everything, every blade, every time.
 
I prefer having the sanding marks going the direction of the lenght all over the blade. And since it is easier i like to bring the finish close before ht and protect it with antiscale compound.
Sharp edges are not nice, but shouldn't be actually rounded, think of it like definitely deburred. The real concerning stress risers in HT are more the abrupt changes in mass distribution at the intersection of different planes (like sharp, unradiused plunges and shoulders and the like).
Usually the deep sanding marks are the remains of hot hogging and that is why they are associated with cracks...all the mess generated during grinding needs to be addressed or will leave his curse to the steel. ;)
But if the steel has been normalized, and thus its microstructure is even, given the correct quenchant, the scratch pattern from grinding could help disrupting the vapour blanket phase ensuring actually a more even quench than the one we may get with highly polished surfaces.
 
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I grind my scales down to the tang when shaping them so there is no need for me to go any higher than 50 pre heat treat.
 
Matt R said:
I grind my scales down to the tang when shaping them so there is no need for me to go any higher than 50 pre heat treat.
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I do the same and that's why all that extra sanding seems like a wasted effort. People always say to not leave deep scratches before heat treat but no one ever actually defines "deep". Since I don't have variable speed on my grinder, I'm not super comfortable with "finishing" things on a belt but I'll roll the dice with this batch.
 
Stezann, I finish everything with the scratches running the length of the blade as well, but it's all done by hand. Since I'm paranoid about the grinder scratches I'm doing that both before and after HT. If that isn't necessary, I'd love to skip it since any sanding I do pre-ht is bound to end up ruined while I shape my handles. I guess what I'm getting at is what constitutes a "deep" scratch - or at least, what sort of deep scratch leads to breakage? 35 grit? 50? 80?
 
This is where a nice set of finish files comes in handy. Shaping and finishing the edge around the choil and along the spine goes much faster with files and there is not a tendency to round the edges over. My files start at 2nd cut and go to finish cut. Its nice if they are tapered and flat on one side and rounded on the other. Do the work with a magnifier lens; when the blade comes out of the heat treat just a few passes with the finish files will result in a beautiful edge.

Fred
 
Fred, thanks for the pointer. I have your jig by the way, it is a handy little thing.
 
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