Another thread wanted to know about beveling a corner chisel....rather than ruin that thread..I'll ask the "Sharpening" question here..

HOW do you sharpen one of these?
Big corner chisel 1.JPG
As I haven't really needed to use this one..yet. 1" on each face.
Big corner chisel 2.JPG
Who ever had this before me....didn't do a very good job..
Big corner chisel 3.JPG
And the bevels are convex, to boot. edges will trim a fingernail with ease...chisel just bounces off the wood....
And, there was a special way to sharpen one of these....anyone remember? something about the corner where the two bevels meet.
The edges on this one are full of knicks....would like a flat bevel, as well...