convex grind?

[tony moyer]

Been having trouble getting a good grind with clean plunge lines any suggestions would be greatly appreciated.

Thank you
Tony

 

[Trace Rinaldi]

I was talking to Michael Vagnino he just got a roto-platen I think they call it from K&G..
It was designed by Ken Onion, and michael said it works REAL well for doing convex blades..
Sort of like a platen with a bit of give..
Might be something you want to look at.. I know I am going to get one soon..

 

[Burt Foster]

True convex grinding where the whole bevel is convex is not easy to do and end up with a really clean knife. Just look at guys who do it that way and have for years - they still have problems with a really clean knife.

One option is flat grinding with a convex edge. In my opinion, it's the best for performance and it's easier to end up with a clean package.

One suggestion, no matter how you do it is remember the most basic rule of making something handmade like a knife with curves. The best way to have a perfectly curved surface is to make several flat ones and eventually connect them. When you make your convex edge (or whole grind), make two grinds (flat) at different angles. Get both sides of the blade even, then put a third grind right at the "ridge" of the previous two. (Kinda hard to put into words). Keep doing that, putting more and more individual flats as you go to finer belts and eventually you will have a very clean convex grind. Resist the temptation to go to a slack belt or whatever until the very end.

I have found that the last step with a variable speed disc grinder running very slow, 320 grit paper and a rubber backer on the disk is the best way to finally even out that last step.

Hopefully that helps. My two cents worth.

 

[Burt Foster]

True convex grinding where the whole bevel is convex is not easy to do and end up with a really clean knife. Just look at guys who do it that way and have for years - they still have problems with a really clean knife.

One option is flat grinding with a convex edge. In my opinion, it's the best for performance and it's easier to end up with a clean package.

One suggestion, no matter how you do it is remember the most basic rule of making something handmade like a knife with curves. The best way to have a perfectly curved surface is to make several flat ones and eventually connect them. When you make your convex edge (or whole grind), make two grinds (flat) at different angles. Get both sides of the blade even, then put a third grind right at the "ridge" of the previous two. (Kinda hard to put into words). Keep doing that, putting more and more individual flats as you go to finer belts and eventually you will have a very clean convex grind. Resist the temptation to go to a slack belt or whatever until the very end.

I have found that the last step with a variable speed disc grinder running very slow, 320 grit paper and a rubber backer on the disk is the best way to finally even out that last step.

Hopefully that helps. My two cents worth.

 

[tmickley]

maybe it's this thing by Rob Frink called a Rotary Platen ?


I just finished grinding a 9" bowie in S30v with it and the darn thing is amazing. I've done a few small blades with it but the big one really impressed me. You can get a nice convex grind that you can shape to what you want -- flatter or fatter, if that makes sense.
I haven't tried to get a clean (top edge) grind line with it but I suppose now I should try to by doing a flat grind top half and convex bottom half grind. Generally, the top edge of the convex grind done with the rotary platen simply blends in. You can take the convex to the top spine or blend it in where you want.

 

[tony moyer]

Thanks,tmickley and Burt

The grinder that I made was made to take all the attachments that Rob makes for his KMG.

Burt that is great advice, and makes sense will try it tonight.

Thanks
Tony