Re: [ATM] Over size laps?

["Mel Bartels" <mbartels@bbastrodesigns.com>]

I stumbled onto oversized laps accidently when my large full sized laps for 
20 inch+ sized mirrors would squeeze out the pitch at the edge and add an 
inch or two to the lap size.  I noticed that the mirror edge became perfect. 
One of the guest speakers at the Bellingham Washington conference (Gregory?) 
talked about Brashear in the 1890's using oversized laps.  And in the 
industry, the 6:5 ratio is well known for maintaining radius of curvature.

I never cold press, so that's not an issue for me and my ovesized laps.  One 
simply makes the lap, face up, as normal.  Move the mirror around every few 
seconds, having it cover different arcs of the edge.  When the lap is in 
100% contact, 'freeze' it by dunking it in cold water.  Then polish/figure 
on!

Keep in mind that when polishing/figuring with normal laps, some part of the 
lap is exposed anyhow.  Oversized laps just expose a tad more.

Mel Bartels 

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