Hand Tools

Subject:
Re: rubbing stones together
Response To:
rubbing stones together ()

AlanWS
"...two will inevitably lead to convex and concave surfaces."

True, but it is very predictable. As a 7th grader I learned how to do it to within 1/4 wavelength of light, or a precision of about 10 millionths of an inch. Lots of people have done this by hand while making telescopes.

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