How to sharpen a head knife

[Art]

Hi Sharp,

The old Convex -- hollow ground -- straight bevel controversy again? Been there done that on the knife-list 10 or more years ago. Convex is great, I like meat behind my edge. However, that is not an easy edge for the average leatherworker to profile, and the newer head knives are getting thinner and thinner to the point that the Convex is getting darned near impossible, not quite, but darned near. While you and I probably have a Bader or a Burr-King where you can get a long run of belt to effectively produce the edge (although the Japanese used to do it with a rock) the average leatherworker doesn't and the hollow or straight is much easier with readily available tools, and very easy to maintain. I do agree that convex is better if you have a thick enough blade to pull it off, the J.Cook blades would be candidates for a convex edge, and even the CSO blades could be done to effect. The last .030-.060 of most convex edges are straight bevels anyway.

Art

Google is a wonderful tool, better than any calculator or trig textbook..... Type in "tangent of 20 degrees" ...

Ok, now since I jumped in being a wiseguy, I have a question....

Why not a convex edge on a head knife? I've been working with knives and knifemakers for a long time and have found that a convex edge is far and away better than a bevel in every case. I made my headknife and convexed it from the beginning so I have no basis for comparison.

As far as I can tell, the knife works perfectly, cuts around curves, skives well and stays sharp; is there something I'm missing?

[Sharpshooter]

Hi Sharp,

The old Convex -- hollow ground -- straight bevel controversy again? Been there done that on the knife-list 10 or more years ago. Convex is great, I like meat behind my edge. However, that is not an easy edge for the average leatherworker to profile, and the newer head knives are getting thinner and thinner to the point that the Convex is getting darned near impossible, not quite, but darned near. While you and I probably have a Bader or a Burr-King where you can get a long run of belt to effectively produce the edge (although the Japanese used to do it with a rock) the average leatherworker doesn't and the hollow or straight is much easier with readily available tools, and very easy to maintain. I do agree that convex is better if you have a thick enough blade to pull it off, the J.Cook blades would be candidates for a convex edge, and even the CSO blades could be done to effect. The last .030-.060 of most convex edges are straight bevels anyway.

Art

Thanks for the answer Art, A while back I did a tutorial on sharpening convex edges.

The same technique can be used to convex a bevel ground blade.

Here's the link. I do have the luxury of having a full fledged knife factory on the other side of the building so I can jump on a buffer to freshen up the edge but the technique in the tutorial works just as well.

I need to make another head knife since my crew has discovered mine they all want one. Old tool technology just never dies...

[TwinOaks]

I'll second the notion that a convex edge is harder for the layperson to maintain.

Now, for the engineers here.....what in hades does driving a train have to do with figurin' out how to sharpen a knife????????

[JAM]

I see by the dates on earlier posts that I am way late in discovering this thread, and the sharpening info is terrific and so useful. I wanted to add my two-cents' worth about honing to keep that razor edge on the blade.

To keep my knives cutting leather like it's butter, I use a hard felt wheel (leevalley.com) dressed with the green compound, on a buffer that's mounted backwards (so the wheel is spinning away from me over the top). It takes a little practice to get the knack of it - but I eyeball the angle (with practice you just know how to stand and hold the knife to get the angle you need so you don't need to eyeball it anymore) and keep the edge of the blade sighted down over the wheel's spindle (if that makes sense) so I have good pressure directly on the edge of the blade. Then I use one or two fingers of my free hand on the body of the blade to lightly press the edge of the blade onto the wheel while I move it from one corner to the other. I hone my swivel knife blades the same way.

[Rawhide]

I see by the dates on earlier posts that I am way late in discovering this thread, and the sharpening info is terrific and so useful. I wanted to add my two-cents' worth about honing to keep that razor edge on the blade.

To keep my knives cutting leather like it's butter, I use a hard felt wheel (leevalley.com) dressed with the green compound, on a buffer that's mounted backwards (so the wheel is spinning away from me over the top). It takes a little practice to get the knack of it - but I eyeball the angle (with practice you just know how to stand and hold the knife to get the angle you need so you don't need to eyeball it anymore) and keep the edge of the blade sighted down over the wheel's spindle (if that makes sense) so I have good pressure directly on the edge of the blade. Then I use one or two fingers of my free hand on the body of the blade to lightly press the edge of the blade onto the wheel while I move it from one corner to the other. I hone my swivel knife blades the same way.

Good info Jam.

I actually use the cardboard paper wheels to keep the edge honed when I'm at home, and I use the four sided strop to fix it up when I'm away from home. However, I wrote the tutorial for those folks that don't have the grinder/buffer to use. This is the old manual way to do it.

Thanks for the additional info.

[Pelallito]

Hello,

I just came across this and enjoyed reading it. Yesterday I came across the paper wheels and will probably order soon. How thick should the blade be for a convex edge? I measured a current head knife and it was 1/16Th thick. So I bought some 1/16 X 4" O1 and I am in the process of sharpening the knife I made with it. I am wondering if I should have gotten something thicker.

I hope that this is a good place to post this and that I am not hijacking the thread. I am going to copy that 4 sided strop soon.

Thanks for the great information.

Regards,

Fred

[Rawhide]

Hi Fred,

I have never measured my head knives, but I'll tell you that I prefer the thinner blades. I don't have a technical reason for such, but I just prefer it, I think it cuts easier. The 4 sided strop is an eye catcher among leatherworkers, and I stole that idea from Peter Main. It is highly functional and I don't know how I got along without it.

[Pelallito]

Hi Marlon,

Sorry to take so long to reply. I just noticed that there was another entry to this thread and read it.

I made the knife, but my heat treating was off. One point cut leather like butter, the other was no good. I took it apart and will reheat treat it.

Thanks for the answer and the help.

Fred

Hi Fred,

I have never measured my head knives, but I'll tell you that I prefer the thinner blades. I don't have a technical reason for such, but I just prefer it, I think it cuts easier. The 4 sided strop is an eye catcher among leatherworkers, and I stole that idea from Peter Main. It is highly functional and I don't know how I got along without it.

[Pablo27]

Great tutorial thanks Rawhide, and I love all the other comments too. So much to learn here. I have had trouble figuring out the correct angle also, what worked for me was to take a protractor and cut an 18 degree angle piece of poster board the hold it between the stone and my knife to check the angle and get used to holding the right angle. It just takes a lot of practice to get it right and get comfortable with the process. I spent hours and hours just sharpening head knifes. Love these forums.

Paul

[Claykan]

This works for me, so thought I'd pass it on. Not to say that it's better than what has already been posted, just another angle to look at.

First off, I run a black Magic Marker along both sides of the edge. This allows you to easily see if the angle you are trying for stays constant.

Then I use a Lansky sharpening system for sharpening my cutting edges. This goes for regular knives and round knives, but we're talking round knives here. You can set the Lansky system for 17, 20, 25 or 30 degrees. I prefer 17 degrees for my round knives since they are only used to cut soft material, and I like them sharp.

The system I purchased comes with 5 stones ranging from 70 to 1,000 grit. I think there is also a 3 stone set you can purchase.

Basically you attached the guide, which has slots for the 4 different cutting angles, to the blade. Then you select the stone you want to use, depending on the condition of your edge. Each stone has a steel rod attached to it. The rod is inserted through one of the slots on the guide, which will keep the angle of the stone constant, and then start working the stone across the blade.

A word of caution! You will be moving the stone against a very sharp and wide blade. Be aware of where your fingers are. I have sharpened my round knives with this system for about 15 years now and can still count to 10. Just pay attention, as you can get the blade to be Scary Sharp!

I haven't looked, but I'm sure that by now there are "You Tube" videos out there where you can watch the system in action, although I doubt it will show round knives being sharpened. If you have any questions let me know.

Fred

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