Re: [ATM] Polishing stroke

[Mike Lockwood <melockwo@uiuc.edu>]

Charles,

Charles wrote:
> I have read at the stellafane web site that a COC 1/3 stroke should be used 
> for all polishing.  I have read on other sites that a "W" stroke should be 
> used for polishing.  I used a "W" stroke for my 6 inch mirror which polished 
> from the center out.  On the 12" mirror, using the suggested normal stroke 
> of 1/3 COC, The mirror is polishing from the outside to the center.  I am 
> grinding MOT, and a cold press for 2 hours prior with no mirror seperation 
> prior to starting each session.   Should I be concerned?  The lap is making 
> execellent contact and if I think it isnt, I stop and repress again.  I just 
> dont want to get into any trouble and end up with some nasty issue I have to 
> spend weeks correcting.  Any comments on this?

The COC 1/3D stroke is an average of strokes, some longer than 1/3D 
and some shorter.  The more random, the better, but stay mostly 
between 1/2D and 1/5D.  Adding some side motion (bit of a W) is a good 
thing, so long as it is randomized too.

The center should show some polish - it should appear shiny to the 
eye, but there will be more pits there than at the edge - after 2 
hours.  If it does not show any polish, something is wrong.  I suspect 
that it is polishing, but lagging the edge, if you have good contact.

	Mike Lockwood

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