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How to sharpen a convex grind by hand?
- Thread starter Naphtali
- Start date
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Is the entire blade one smooth bevel like an Opinel, or does it just have a convex edge bevel as found on many flat gound ABS bowies? The basic method to sharpen both is the same only the implementation is slightly different.
If the entire bevel is convex then place the spine of the knife on the far side of the stone and as you pull it back towards you, roll the knife up so that at the end of the stroke the edge is making contact. This sounds a lot harder to do than it is in practice. Now just lift the blade up, turn it over and do the same thing pushing the knife away from you.
This assume that you want to keep the full convex bevel and want to sharpen the whole thing each time. In reality unless the steel is really easy to machine this is a massive waste of time and only really practical with power tools. D2 is one of the more difficult to machine steels and full honing the primary grind is a great way to waste a lot of time.
If just the bevel is convex, or you just want to sharpen the edge on a full convex grind (which is vastly more efficient) you do almost the exact same thing except you lift the spine of the knife so just the edge makes contact. This is harder feedback wise as you don't have as much a tactical responce. I prefer to use small stones and work the knife directly.
If you have a persistant burr problem then when you switch grits take just 1-2 passes on the finer grit at an elevated angle to clean off the burr then go back to the regular work on the stone. On tool steels with proper hardening this is usually not needed unless the edge was really over stressed.
Thom also posted a method of edge-into sharpening to produce convex edges recapping some notes Alvin made on rec.knives awhile ago which is basically the same as the above but in reverse direction and produces a more optimal edge but can be harder to do well.
Note after you sharpen just the edge a number of time you will note it will thicken and start to grow more distinct from the primary grind. It is now time to take your most x-coarse stone and work the primary grind as described in the above, until the edge bevel has been reduced to its optimal width. There is no need to finish polish the primary, but you can if you have the time. It will just burnish smooth in use.
-Cliff
If the entire bevel is convex then place the spine of the knife on the far side of the stone and as you pull it back towards you, roll the knife up so that at the end of the stroke the edge is making contact. This sounds a lot harder to do than it is in practice. Now just lift the blade up, turn it over and do the same thing pushing the knife away from you.
This assume that you want to keep the full convex bevel and want to sharpen the whole thing each time. In reality unless the steel is really easy to machine this is a massive waste of time and only really practical with power tools. D2 is one of the more difficult to machine steels and full honing the primary grind is a great way to waste a lot of time.
If just the bevel is convex, or you just want to sharpen the edge on a full convex grind (which is vastly more efficient) you do almost the exact same thing except you lift the spine of the knife so just the edge makes contact. This is harder feedback wise as you don't have as much a tactical responce. I prefer to use small stones and work the knife directly.
If you have a persistant burr problem then when you switch grits take just 1-2 passes on the finer grit at an elevated angle to clean off the burr then go back to the regular work on the stone. On tool steels with proper hardening this is usually not needed unless the edge was really over stressed.
Thom also posted a method of edge-into sharpening to produce convex edges recapping some notes Alvin made on rec.knives awhile ago which is basically the same as the above but in reverse direction and produces a more optimal edge but can be harder to do well.
Note after you sharpen just the edge a number of time you will note it will thicken and start to grow more distinct from the primary grind. It is now time to take your most x-coarse stone and work the primary grind as described in the above, until the edge bevel has been reduced to its optimal width. There is no need to finish polish the primary, but you can if you have the time. It will just burnish smooth in use.
-Cliff
Clifford:
Many thanks for a clear, concise reply.
Sharpening is nearly impossible to mess up permanently. If my sharpening job is a poor one, do it again. And, from your reply, it appears that as the sharpening process wears away blade, the edge configuration remains constant -- that is, the edge DOES NOT become thicker and less efficient with use.
Okay, now for a difficult question: Is there available two listings for makers of knives with convex grind -- one for production or limited production makers, one for custom makers?
***
Parenthetically, interesting side effects of the grind appear to be:
1. If you're paranoid about corrosion, as I kind've am, the act of sharpening automatically removes it.
2. Paying extra for a mirror finish is a pointless expense. First resharpen and -- BEHOLD -- finish is gone.
Many thanks for a clear, concise reply.
Sharpening is nearly impossible to mess up permanently. If my sharpening job is a poor one, do it again. And, from your reply, it appears that as the sharpening process wears away blade, the edge configuration remains constant -- that is, the edge DOES NOT become thicker and less efficient with use.
Okay, now for a difficult question: Is there available two listings for makers of knives with convex grind -- one for production or limited production makers, one for custom makers?
***
Parenthetically, interesting side effects of the grind appear to be:
1. If you're paranoid about corrosion, as I kind've am, the act of sharpening automatically removes it.
2. Paying extra for a mirror finish is a pointless expense. First resharpen and -- BEHOLD -- finish is gone.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Naphtali said:Sharpening is nearly impossible to mess up permanently.
Yes, the only significant concern here would be using power tools and overheating the blade seriously, by hand, the biggest issue is losing the curvature which can happen if you work the blade unevenly, just try to keep the edge always perpendicular to the stone.
...that as the sharpening process wears away blade, the edge configuration remains constant -- that is, the edge DOES NOT become thicker and less efficient with use.
Yes, full grind sharpening preserves the edge angle and thickness, the entire blade slims down very slowly, and thus the cutting ability tends to improve with sharpening, though the blade as a whole gets weaker due to decreased cross section, note both of these are *very* slow processes, think years to make any significant effect.
Is there available two listings for makers of knives with convex grind -- one for production or limited production makers, one for custom makers?
There are not a lot of production convex grinds, Bark River and other such traditional patterns, folders like Opinels and there have even been some stainless patterns. With customs, pretty much any custom maker could do that grind, some prefer it standard. This comes up in the main forum constantly so a search should turn up lists.
-Cliff