[ATM] Figuring with sub diameter lap

[jonathan_bishop at sbcglobal.net (Jonathan Bishop)]

How big is your subdiameter lap?

--- Richard Ozer <rozer@pacbell.net> wrote:
> I'm working on a 14" mirror with a subdiameter lap. 
> I would highly
> recommend making a full sized lap.  However, if you
> want to give it a try
> with the sub-diameter, then work with a W stroke. 
> Center over center with a
> subdiameter tool will add correction, a W stroke
> that concentrates more on
> the edge than on the center will tend to flatten it
> out.
> 
> If you have a ronchi grating, you'll find it quicker
> to use than a knife
> edge for monitoring your progress.
> 
> RO
> 
> ----- Original Message ----- 
> From: "Jonathan Bishop"
> <jonathan_bishop@sbcglobal.net>
> To: <atm@atmlist.net>
> Sent: Monday, March 08, 2004 5:14 PM
> Subject: [ATM] Figuring with sub diameter lap
> 
> 
> > Hi,
> >
> > I am currently figuring an 8" F5 mirror using my
> old
> > 4.25" lab left over from when I polished my first
> > mirror. The defect I am working on is a sever
> > overcorrection, so I am attempting to reduce the
> 70%
> > zone.
> >
> > So far it is going well, which is encouraging. I
> am
> > wondering whether many others use a sub diameter
> lap
> > to figure with. It seems reasonable as you can
> easily
> > direct you polishing to the zone you need to work
> on.
> >
> > Jon Bishop
> > _______________________________________________
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>