I recently purchased a set of expensive Japanese chisels. I previously had several less expensive Japanese bench chisels from Japan Woodworker, and no problem flattening the backs. For this expensive set, I took them to a workshop with Garrett Hack. I only needed 1 for the course. He suggested I flatten the back with a not so course water stone to start, but then I showed him how it was not evenly reaching the edge across, and so the plan was course to fine. It was a fairly narrow chisel and I got is nice and sharp, but it took awhile. No time to work on the other chisels during the workshop as I was kept busy.
When I came home this weekend, I went to sharpen the rest with my NanoHone waterstones. Goal was mirror finishes and sharp. As I started to flatten the backs, especially the wider chisels, I noted that I was not getting the scratch pattern to reach across. This is shown in the pictures. I got nowhere with grits less than 200 (70u) and with that course grit it seemed to take forever. More problematic was that although with time the surface area not getting touched got smaller and smaller, I was removing quite a bit of material on the other side. However, I know that I must get the back flat all the way across and if that does not happen with a courser grit, the finer grits will not make that happen. I never had problems like that with other chisels or plane blades.
To be sure, I was very frequently flattening my stones, and I was very aware not to put uneven pressure, especially since I noted the low spot tended to be to the left when viewing the back. I even tried to vary how I was moving the chisel across the stone, and as I suspected, it did not matter. It did not matter if I tried to flatten the entire back or limit to the area more towards the edge. It was flat on the flat stone, and with the wider chisels in particular, not so hard to keep the bottom in contact.
I really think these chisels came not so flat unless someone can suggest something I could have done to cause this. To be sure, I was using flat stones and not applying uneven pressure.
Thoughts?
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