[ATM] Re: ATM Digest, Vol 4, Issue 8

[artbianconii@blast.net]

On 7 Apr 2004 at 23:00, atm-request@atmlist.net wrote:

Supporting thin mirrors for testing (Mark Cowan)

"Is there good contact between the mirror and board over the entire
 back and how do you determine that?"

At the MidAtlantic Mirror Making event this year, Steve Swazie used Bill 
Hanagan's mirror bench for all the tests. All the mirrors rested on a fabric web 
sling. Nothing novel here; it's a popular support method.

What I found novel was that Bill had affixed three tapered strips of wood to 
the front face of the mirror support in a radial pattern. The support sling is 
adjusted so that the center axis of the three radials is coaxial to that the of  
mirror being tested. Each strip was about 10 inches in length, perhaps a half 
inch wide and tapered uniformly in thickness from perhaps a half inch to a 
quarter inch. 

The result of this was that no matter what diameter mirror you were figuring, 
it only touched lightly at three, equidistant points on it's outer edge.

Art Bianconi

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