Re: [ATM] Spherometer (Francis J. O'Reilly)

[Michael Lindner <mikell@optonline.net>]

David Janello wrote:
> For folks looking at doing this there are some good
> buys on mitutoyo digital dial indicators on ebay, just
> got a 0.00005 resolution dial gauge for 57- that I
> plan on using with the 1800destiny sphereometer.

FWIW I did the following:

I bought an 8" (1/2" bore, IIRC) cast pulley from McMaster-Carr, mounted 
it on a shaft clamped to my drill press and drilled 3 holes through 3 of 
the spokes. I then had 3 holes fairly equidistant from the center. I put 
a screw through one side of each hole into a spacer, and epoxied a 1/4" 
ball bearing in the bottom of the spacer to make 3 accurately placed 
feet. I put a bronze sleeve bearing into the hole to fit my dial 
indicator (3/8" i.d. IIRC). The set screw on the pulley holds the 
indicator snugly. I use a flat piece of glass for a reference and Using 
a known focal length mirror I was able to calibrate it.

http://astro.umsystem.edu/atm/ARCHIVES/AUG02/msg00219.html

I have access to a more accurate commercial spherometer now, but for 
several years this one served me well.

Clear skies.
-- 
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net
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