Search:

I found on his website that the crown is 'just over .4 mm over a 200 mm stone', so my math was pretty much right on.

How much crown can you measure this way? I've been using .5 mm crown over an 8" length for my math musings.

Actually it would be more like a 66 foot diameter sphere. The math assumes an 8" long hone with a`.5 mm crown.

Jarrod has a video of how he did his first ones, but if you study techniques for lapping telescope mirrors you will get a much better understanding of the process. Basically, two stones lapped...