Holding 1/2 of a thousandth of an inch may sound impressive, buy with
some time, a good calipers and an optivisor it is not too hard to do.
Did a geometrically perfect hexagon out of lapis, just to see if I
could do it, a double sided cab wth a full curve on both sides and an
almost undetectable meeting line.
Overall, took about 2-1/2 hours in 3 sessions. By hand, no jigs.
Hey, if you can’t turn out a perfect stone every once in a while for
fun, after 25 years of cutting,
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Denver, Colorado 80207