Re: [ATM] Glass cutting speed

["Donald Good" <donald.good@comcast.net>]

After searching thru the archives, some ATM web sites, and some articles in
Advanced Telescope Making Techniques (edited by Allen Macintosh), I found
that glass cutting speeds for circles can vary widely and still be
successful.  Confining the search to perimeter or plug cutters (like hole
saws rather than twist drill bits) and calculating the perimeter speed (for
meaningful comparison) from rpm and diameter data, the perimeter speed
varied from 250 inches per minute (ipm) to nearly 4400 ipm.

The slow speeds seemed to group around 1400 ipm and used "wet" loose grit
and water in a slurry that was applied periodically as from a squirt bottle.

The fast speeds are a small group around 4200 ipm that appear to run the
cutting edge "submerged" in a circular channel fashioned from clay or putty
or something similar about an inch deep and filled to a depth that would not
overflow at speed, but sufficient to act as a damping fluid to catch what
would be spray or splatter from the "wet" squirt bottle method.  This speed
is also reported to have the advantage of keeping 80 grit suspended in the
slurry (2 oz grit to 2 cups water).

To calculate rpm, choose a perimeter speed S and divide by pi*D: rpm =
S/(pi*D).  Then allow some variation for the rpm choices on the available
equipment.

       inches             mm
       ipm    rpm         mmpm     rpm
Fast   4200   1340/D(in)  106800   34000/D(mm)
Slow   1400    450/D(in)   35500   11300/D(mm)

(above numbers rounded for convenience)

Clear skies

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