Convex Edges

[brute]

I have a question, has any one come up with a jig or a devise to grind convex edges, with a Tormek?

[Ken S]

I would use the slack belt part of the belt on a belt grinder for convex edges.

That stated, the "hollow grinding" issue with a large Tormek wheel is overblown. The hollow ground, concave edge mindset goes back to when most grinders had six inch diameter wheels.

Ken

[John_B]

Another issue I see is that illustrations are often not to scale so that the edge geometry can be easily seen in the viewer's mind.

[jeffs55]

When you use anything to grind with you are going to produce a negative image of the device you are using. So if you are using a round wheel, the negative would be a concave image. You have to do what Ken said but in reality the slight concavity of the edge you are producing is unlikely to ever cause a problem. I get your drift though.

[Ken S]

I sharpened one of my "sharpening chisels" with my T7/8 and another with my T4. Comparing the two visually (naked eye), any attempt to determine which was which would be at best a guess. Looking very carefully using a rule as a straightedge, I could see a faint hollow grind (I think.) I realize that in theory, these edges are both concave; however, if I cannot see it, I don't worry about it.

Ken

[jeffs55]

You are right Ken. That is sort of what I say when I am putting up one of our yard greetings. Regarding straight lines as in a line of letters spelling out Happy Birthday. I make it straight to my naked eye and say to myself that if I can't see it, no one else can so it is straight!

[Ken S]

Great comment, Jeff!

Ken

[kwakster]

One would need an ovalized stone to do convex edges on a Tormek.
The mock-up in the pics shows how this would work.





(Pics stolen from forum member Jan)

[RichColvin]

Carl,


I have seen two cases where convex edges are desirable.

   
• Some wood carvers, especially chip carvers, like their knives to have a convex edge.  They say it helps to keep it from getting stuck in the wood.
• Some axe men (people?) like the sharpened edge to be convex (probably the same reason).

To do this on a Tormek would require an approach like achieved using a platform, and rotating the handle as you go.  That is no different that sharpening on a flat stone though. 


So it is possible, but for most tools I question the value.  Having a repeatable edge has far more value.


Kind regards,
Rich

[brute]

Hi Rich
I have 5 Bark River Knives, two of witch I have ground regular 15 degree edge. Bark River calls for convex edges on there knives. I know that there are hand sharpening systems that can grind convex edges. I was just wondering if Tormek guys had a devise or a process.