Edge thickness question...

[J. Doyle]

I've read many posts on how thick to take the edge before heat treating. It seems the standard is about .040" (about a dime's thickness). And I agree and that's about the thickness I go to.

My question is: Do you guys then go thinner after heat treat but before the final cutting edge is put on?

I've been sharpening knives most of my life and I'm no stranger to sharpening. I feel I have a pretty good understanding of how edge geometry affects cutting performance. I make mostly hunting and utility type knives and the edge seems fine for those but I see a lot of guys say their knives are 'absolutely razor sharp' or 'scary sharp' but they have this same geometry (or basically). I don't see how this is possible. When I put a cutting edge on a knife that's down to .040", I can get it to shave hair but it's not like a razor and they won't just slice through paper cleanly. .040" seems like it's fairly thick for a truly razor edge to be applied to. It makes a great working edge for a hunter or utility/bushcraft but my hunters out of 3/16" or 5/32" stock with a .040" edge don't get 'scary sharp'. If I thin the edge out to make them that way, it seems like too thin of an edge for that type of knife prone to chipping or other damage.

WHat do you guys think? Am I doing something wrong? Looking forward to your responses.

 

[stephanfowler]

YES

on a small knife I take the edge down to .010 / .015

on a large bowie type I take the edge down to .020 /.025



then roll the convex edge in to sharpen

 

[RMcClellan]

Are we talking about a hollow grind or a flat grind? I was told it is difficult to get a true convex edge on a flat ground blade that has a thin edge, which makes a lot of sense to me. This is a question I posted here the other day. I still don't have a clear understanding of what everyone is refering to when they say "edge geometry". A convex grind I have a clear understanding of, but that term (edge geometry) eludes me. There has to be a specific angle to the edge that can be measured some how. Right?

 

[stephanfowler]

Are we talking about a hollow grind or a flat grind? I was told it is difficult to get a true convex edge on a flat ground blade that has a thin edge, which makes a lot of sense to me. This is a question I posted here the other day. I still don't have a clear understanding of what everyone is refering to when they say "edge geometry". A convex grind I have a clear understanding of, but that term (edge geometry) eludes me. There has to be a specific angle to the edge that can be measured some how. Right?

a "true" convex grind does not have any flat areas, it is a constant curve from spine to cutting edge.

 

[Mike Quesenberry]

YES

on a small knife I take the edge down to .010 / .015

on a large bowie type I take the edge down to .020 /.025



then roll the convex edge in to sharpen

I'm with Stephan, I like my edges thin. I usually do a flat grind down to .015 - .020 and sharpen. Sometimes I roll the edges in like on a convex grind till it's sharp.

 

[J. Doyle]

Thank you, gentlemen. :thumbup:

That could be my issue right there. I mic'ed these edges and I need to take them down some after heat treat.

 

[RMcClellan]

a "true" convex grind does not have any flat areas, it is a constant curve from spine to cutting edge.

So the edge geometry is actually and arc, not an angle, Very enlightening!!!! I have been doing something similar, but instead of using the slack belt with the platen off, I was using the top of the belt behind the platen attachment. I'll have to look at the knives I have here that I've done to look at how the edge is, but I think I've been doing a convex or at least a modified convex edge the whole time. All I know is that I have been getting my blades sharp as shi...err poop. Good to know I was on the right track, I think what everyone is saying is to use the slack belt area at an acute angle and roll it toward the edge. I think you said earlier was to take the edge down to the thickness of a dime. That seems to me to be pretty thin, but I will need to see it and try it out to actually understand how well that will work for me. How well will the thinner edge work for a larger "chopper" type of blade? This is great information, please keep your process and tips coming, Thanks so much, Rex