Best config for good convex edge?

[Jack O'Neill]

Ok. I thought with a coined name like that .. there must be something additional added...I googled and did not find anything unique.

thanks

Moran story .I read an article years ago by this man .he got so excited when he found this sharpening method that he sharpened everything in the house including the lawn mower blade . Then he mowed the lawn and cut his toe off .

 

[Gossman Knives]

Jack, the fine SB does a great job. I have a 2x72 leather belt but just can't work with it as well as the SB. I hand sharpen with a diamond rod and leather strop.
Scott

 

[koyote]

i do 100% slack belt on the convex edges. I have a coote 2x72 with an 8 inch wheel.

I most often do a deliberately *variable* convex grind, working for a bit more obtuse angle near the tip and shallowing out as I reach the middle of the blade, then sometimes a bit more obtuse right near the grip. This is give a bit stronger edge for the tip and right near the handle where you have the best leverage for power cuts. On boning or skinning knives i try to keep it shallow all the ways out.

I sometimes do a full convex grind, most often something that looks like a convex scandi grind. I can't explain very well how it works, but the angles change with your position on the belt, the belt stiffness and where your fingers are on the blade. I mostly go for a feeling of void and just let it happen, but that's not helpful for describing a technique.

I started doing convex edges on a 1x30, and I'd recommend if you are going to go completely slack belt, start with a 1x42 or 1x30 and then move up to the 2x72. the 1x will go slower, but that gives you time to get the feel of it.

I haven't tried scott's method of doing a flatgrind first. I might have to

edit-

oh yeah, i finish out to 600 on the belt and then strop with black rouge and then strop with red rouge. seems to work

 

[jdm61]

FYI, Bill Moran did not do his convex grinds on a slack belt. He pretty much did everything free hand and by calibrated eyeball using what we would consider archaic gear like a big emery wheel and a Wilton grinder. He also did a LOT of vertical grinding on 3 inch small wheels, including one with a soft foam cover. Charles Ochs is the only other guy that I know of that grinds blades similar to the way Mr. Moran used to. In his knifemaking video, Mr, Moran said that doing a convex grind with a slack belt left it TOO convex. The full height convex grind on his later knives are very subtle, more so than even some of the knives done by his students/friends. They are also scary sharp.

 

[nutria_man]

i do 100% slack belt on the convex edges. I have a coote 2x72 with an 8 inch wheel.

I most often do a deliberately *variable* convex grind, working for a bit more obtuse angle near the tip and shallowing out as I reach the middle of the blade, then sometimes a bit more obtuse right near the grip. This is give a bit stronger edge for the tip and right near the handle where you have the best leverage for power cuts. On boning or skinning knives i try to keep it shallow all the ways out.

Now that is a neat idea...thanks for the tip

 

[Jack O'Neill]

I recently made an attachment for my 2x72 belt sander that leaves about a 2-3" section of the belt unsupported on the back ( slack ) also went to an X weight belt down to a 600 grit . This is has close to a tight convex edge I could think of . I use a fine diamond rod to remove the burr . have not tried the buffer yet for the burr removal . I hear that a ceramic rod works well . anyway , the edge not only shaved the hair on my arm , it also removed some skin . Must have been a good edge . This post has been a great exchange of knowledge .

 

[Gossman Knives]

FYI, Bill Moran did not do his convex grinds on a slack belt. He pretty much did everything free hand and by calibrated eyeball using what we would consider archaic gear like a big emery wheel and a Wilton grinder. He also did a LOT of vertical grinding on 3 inch small wheels, including one with a soft foam cover. Charles Ochs is the only other guy that I know of that grinds blades similar to the way Mr. Moran used to. In his knifemaking video, Mr, Moran said that doing a convex grind with a slack belt left it TOO convex. The full height convex grind on his later knives are very subtle, more so than even some of the knives done by his students/friends. They are also scary sharp.

This is the reason why I flat grind first. Doing it on the slack belt only takes a longer time to grind and is "too convexed" like an axe grind. The slack belt only is fine for thinner stock but flat first, rotary second gives a subtle convex grind and better full grind geometry.
Scott

 

[siguy]

i often work similarly to scott gossman, i do a flat grind almost all the way, then take some passes to start to convex it, then i even everything up on a slack belt then start going down through the grits with a variety of final finishes...

-down to either 15 or 9 micron belt, followed by a cardboard wheel with semi-coarse compound, followed by a cardboard wheel loaded with tripoli (finer than the other) then a handstrop with tripoli compound.
-down to 120 grit belt, then to a medium scotchbrite wheel, followed by the coarse compound cardboard wheel, followed by the hand strop.
-(by hand) a medium grit stone to set angle, 400 grit sandpaper to smooth and convex edge, up to around 1200 grit to polish, followed by tripoli strop or .5 micon film

all create the same effect, a highly polished incredibly sharp convex edge. in my experience, there is nothing better. the consistent and even finish comes with practice, as with everything the more you practice the more consistent your results will be.

as far as why a convex edge is good for things besides chopping blades...convex edges give you an edge that can be finished to a huge number of grits, can be varied based on use easily, and can be sharpened effectively with about $15 worth of materials.

the convex edge also allows the edge to be thinned quite a bit, but when sharpening it has a slight microbevel caused by the convex shape that improves the stability and durability of the edge. also, a high polish parts materials better and does not have such large "micro teeth" as coarser finishes, meaning that it is less prone to chipping, making for an even more stable and durable edge.