[ATM] Spherometer

[bobmay at nethere.com (Bob May)]

There's a web article on making spherometers but I don't remember who has it
now.
Make the spherometer large enough that you can measure to the accuracy
needed for the curves.  A large diameter near the diameter of the lens may
be used without fear and will allow for the usage of less accurate dial
indicators which have a larger travel.  Also allow for the slipping of the
indicator mechanism in the middle if you can't get a lot of travel of the
measuring device.
1" diameter is way too small for a spherometer for lensmaking.  I use 4"
ones as a moderate accuracy spherometer for measuring mirrors and would
probably turn one out of about 5.5" for a 6" lens so as to obtain max.
accuracy for a really good lens curves.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
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