I have an old TH Witherby corner chisel. It definitely needs sharpeing and doesn't look like it's had it in a long time. I don't think it was maintained properly. the cutting edges are not square. In the corner it flares out below the cutting edge of the sides. I saw a new Barr corner chisel and it looks similar. So how the heck are you supposed to sharpen this chisel? What to use? What technique? Can it be done by hand without a machine? I'm assuming that you first start by flattening the back sides like on a regular framing chisel.
Thank you,
Brad