Re: [ATM] Grinding questions

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

John Stephen wrote:
> What sort of things will places like this need to know, or more 
> specifically, what do I need to ask for?  I feel a little intimidated 
> about approaching a serious manufacturer like this (or any others 
> suggested by the group) since I'm just a beginner ATMer.  I'm sure I'll 
> have to know what type of glass, the diameter, and the thickness, but 
> how do I ask for an initial curve?  ATMer's call it hogging out, but 
> what do the professional optical shops call it?  Will they want to know 
> the desired F ratio or SAG or what?  Also, are there any services I'd be 
> wise to ask specifically for such as edging?

There is a tolerance associated with the pregenerated curve.  As it
was described to me, tolerances are usually expressed such that a
"matching" convex and concave surface meet at the edge, i.e.: the convex
surface is the basic curve minus zero and plus a percent tolerance (3%),
while the concave surface is plus zero and minus the percent tolerance.
This is a form of pregeneration is a slight overshoot.  The user slowly
brings them back to contact during the finer stages of grinding.


-- 

Rick S.

http://users.rcn.com/rflrs

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