RE: ATM Unchanneled Lap Polishing

["Bertapelle, Ken" <Bertapelle.Ken@tci.com>]

Hello Bob,

When I made my lap I followed the procedure in Tesereaux's book,
which is to pour the pitch into a set of molds.  This produces
a set of sticks of pitch, which are 15" x .75" x .25".  Then cut
the sticks into tiles .75 x .75 x .25, and melt these individually
to stick them on the tool.  

This procedure seemed to work pretty well, however, this was the
only lap I've ever made, and I'm not sure how it compares to the
other techniques I've read and heard about.  Anyone out there
have any comments on the comparison?

- KenB

> -----Original Message-----
> From: Dwight Elvey [mailto:elvey@hal.com]
> Sent: Tuesday, June 15, 1999 12:35 PM
> To: atm@shore.net
> Subject: RE: ATM Unchanneled Lap Polishing
> 
> 
> 
> Bob Prabowo <BOB@bahana.co.id> wrote:
> > 
> > Hmm, this is interesting. I have to remake my lap, for it's 
> too hard.
> > And the first thing that came into mind is the channeling process. 
> > 
> > I'm polishing a 13" mirror, the question is: will 
> unchanneled lap work
> 
> 
> Hi Bob
>  In order to keep from forming bubbles at the center of the mirror,
> you'll most likely need to channel it initially. If you do it
> like John Dobson does, it isn't too hard. If you haven't seen
> it done, see if you can get a his video.
>  The method is to use a piece of wood dowel and press it into
> the pitch while it is still soft. Make repeated cycles of
> pressing on the mirror and opening the channels again
> with the dowel until you are happy with full contact. Then,
> before the pitch hardens, press the to close the channels.
> Use some CeO and water to keep the lap from sticking to the
> mirror while doing this and wet the dowel as well.
>  I tried making the lap face once without channels and ended
> up with a big air bubble at the center of the mirror.
> Dwight
>