Convex Grind Tips, Tricks or Hints?

O

only1asterisk

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Feb 20, 2008
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I want to try making my next couple of knives using the convex grind. Anybody got advice for speeding up my learning curve? Is there a good how-to out there that I should read?

David
 
Convex grinds are generally done on a slack belt attachment. Problem I've found strickly using the slack belt is that the area just about the edge is too thick. Flat grinding first to a specified thickness then switching to the slack belt will give you a better grind unless the spine thickness is 1/8" or less, then slack belt only grinding will work fine. Or get the rotary platen for the KMG. I still flat grind first with thick stock even using the rotary.
Scott
 
the easiest way imo is to first establish the blade geometry that is wanted by making light hollow grinds on the contact wheel. leave a little extra steel. then move to the slack belt area to blend all the small hollow grinds together. relying on the belt tension in the slack belt area to control the blade geometry usually gives a cross section that is fat in the middle and thinner at the spine.
 
On the blades that I use a convex grind on, I flat grind first, fairly thin on most knives and not quite as thin on choppers, and then I use a real tight slack belt to make it convex.

Todd
 
I also flat grind first to establish the basic blade geometry and then finish the grind on the slack belt. Don't push too hard or you'll end up with a thinned edge and a thinning spine. I grind edge up and rock the blade from edge to spine gently while moving it across the belt. This helps keep me from getting uneven spots. Just be sure not to rock too far to the spine or you may round over your spine a bit. Also, be extremely careful around the tip. I usually will leave it to the last. Don't pull or rock the tip into the belt, or a little whisp of smoke and curled over blue steel will be what you've got left and you will have to reshape the end of the knife.

Also, if you are working to clean up plunges on the slack belt, keep the blade in the same plane as the belt. Don't bring the tip away from the belt to try and force the edge of the belt into the plunge. If you do this, you will end up with a groove just in front of the plunge and it is a bear to grind or sand out. Keep the blade in line with the belt.

--nathan
 
If you are going to the trouble to put a flat grind on a blade, why switch to a convex grind to finish it? Can you put a sharper edge on a convex grind, than on a flat ground blade? I don't think so!:confused:

Fillet knives profit from a convex grind because they are thin in both blade width and cross section.

Fred
 
Fred,

I'll use a convex finish on a partial flat grind because I find it more pleasing in appearance on some knives. Also, I will flat grind only partially, and then switch to a convex grind. This gets my geometry started while still leaving a lot of meat to be removed with the convex grind allowing for more steel behind the cutting edge. For me, this is beneficial for a chopper or heavy use blade where keeness in edge (ie, shaving my face) is less desireable than durability, toughness, and even a heavier weight.

Some knives I will flat grind almost fully and then still finish with a slight convex grind as I just like how it looks.

--nathan
 
I think the convex edge is more durable and just as sharp as a beveled edge. It is a good way to finish off whatever grind you are doing.

Jerry Hossum does deep hollow grinds with convex edges on his knives, with good results.
 
Actually, I can put an equally sharp edge on my flat ground and my convex ground blades. I flat grind first because it helps me to get a thinner convex grind with my set up. I don't use a full convex grind on many knives. Instead, I use a flat ground primary bevel and a convex edge on most. I put a convex edge on every knife that I edc, even my old Case Trapper. Properly done convex edges just cut better to me, though they do take me more time to sharpen than a conventional bevel.

Todd
 
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