This one for James or Peter I think. I've got me a scorper so that I do something akin to Guilloche enamelling, which I love so much I used to collect it. I know that guilloche was engine turned, I just want to do something similar.

Anyway - grinding tools has never been a strong point for me; when I was woodturning I had a nifty Sorby jig that allowed me to set angles and stuff - even a duffer like me could use it. Now of course, sans jig, I need to grind my scorper. What angle and shape should the business end be? Any tips gratefully received.