chisel with convex back

[Mark Ketelsen]

I am looking for a good way to flatten the back of a 1" chisel that is slightly convex. I know that with convex plane soles some people file the high part to make a concave surface before lapping. Is there a effective way to do something similar with a chisel?

Thanks.

[Terry Beadle]

It's important to know what kind of chisel. A japanease chisel takes a completely different technique to correct than a domestic or English chisel.

Assuming a domestic chisel, what I'd recommend is to determine how much of a convex curve there is. If it's a big one, say more than 10 thou, then I'd warm it up to about 150 to 200 degrees in a toaster oven and then put it on an anvil surface and give it a few licks with a 2 pound hammer. Probably even take it back to where it might be very very slightly concave. Then plunge it in cold salt water. Check it's flatness by rubbing it on 220 grit sand paper laid flat on a cast iron or granite surface.

If the convexity is slight, I'd use a flattening steel plate and 60 grit to quickly take it down and finish with diamond xtra course, then fine and then from 800 grit water stones thru 10000 grit.

If you don't have the above, then use the scary sharpe method with low to high grit papers.

This is free advice...maybe worth it! Hoot!

Good luck and let us see some pic's if you can while you work through it.

Take care and enjoy the process as it's the best part.

[Gary Herrmann]

Try a belt sander with 80 grit on it. A number of my greenlees were somewhat convex, some still are. They're for general use, so I didn't get too worked up about it.