Flat to Convex

[JGarrison Knives]

Whens the point of no return when starting out doing a flat grind and then changing your mind to convex? Is there a formula to follow regarding knife thickness and width and how much youve flat ground so far? I have a 2" wide, 1/4" thick recurve piece that I started to flat grind and now Im thinking convex. I have flat ground about half way and I still have room to work with on the edge end.

 

[Joe Calton]

I do mostly convex grinds, with some flat grinds. but everything starts out flat ground to save time. but I leave the edge pretty thick going into ht, then after ht I turn the flat grind into convex, but I dont have a formula or anything and I prefer kinda shallow convex grinds.

you could try holding the blade up against your slack belt where you do your convexing and eyeball it to see if you have room. or maybe flex a piece of wire over another convex blade with the same grind as what you want to put on this one and then use it a guage to see what would happen to the current one.

about the worst that can happen is that you run out of meat at the edge and the blade becomes narower than you wanted when you get the grind finished.

 

[JGarrison Knives]

Thanks Joe, I didnt think of it in terms of running out of meat and becoming narrower.

 

[Daniel Fairly Knives]

I take mine to a nearly finished thickness (but still thicker than normal) then convex.

I usually consider a convex a slimmed down flat grind versus a fatter axe grind but it depends on the intended use.

An axe style convex is best done with lots of thickness and is great for splitting wood or hard use tasks. The slimmed down version is great for overall knife usage.

That is just a perspective on it and there are lots of ways to remove the metal.

 

[Stacy E. Apelt - Bladesmith]

I do it like Daniel.
I flat grind the blade, and then slack belt the edge. To the eye, it looks like a flat grind. Upon close examination, there is no secondary bevel.

 

[grizzled gizzard]

To me, what Stacy is describing is a flat ground blade with a zero grind convex edge. That's very feasible.

You determine the amount of convexity by how far you take the flat grind.

I think that's the main point.

Most guys zero grind their convex blades, like Bark Rivers. That doesn't mean you have to have a convex edge on a convex blade, but it's typical.

 

[JGarrison Knives]

The convexing went well but I might borrow my freinds rotary platen after heat treat, Im a little concerned about the plunge area if I just do it with a slack belt.