Recess Tool
I have just started to make some salt and pepper mills using the CrushGrind mechanism and realised that a precise recess needed cutting inside each mill to take the locating ridges. There are special tools for doing this but at a cost.
The other option is of course to make one if you have a bench grinder. After raking around in my tools drawer, I found an old Marples chisel that I had been using for rough jobs and so had a go at grinding it to shape. It was surprisingly easy on the white stone of my grinding wheel and in about 10 minutes I had a recess tool and a saving of £33. It worked perfectly.