Re: ATM foucault tester built

[Dale Eason <atmpob@yahoo.com>]

You don't need a mold but many people like them.

I use a 1/4 inch diameter wooden dowel soaking wet and
smeared with CEO to keep it from sticking to the
pitch.  I press it down onto the lap while it is still
soft to make each groove.  Then put the mirror on it
to form the top.  This usually closes up the grooves
somewhat.  Then I press the stick into the groves
again.  Then press the mirror again.  I keep doing
this until the lap is well grooved and has pretty good
contact with the mirror.


If the lap gets too cold while doing this I heat the
tool and lap in hot water to soften it again.

On my 16 inch mirror I use 1/8 thick by 1 inch
aluminum strip to do the pressing.  Pressing the thin
edge into the pitch.  It only took me about 15 minutes
to form the grid by heating the pitch in 140 deg F
water about 10 minutes.

Dale Eason
--- c f <quantemlp@hotmail.com> wrote:
> 
> Hello to all,
> 
> I sat down last saturday and built a foucault tester
> from the stellafane 
> site ( 
>
http://www.stellafane.com/atm/atm_foucault_tester/atm_tester_plans_1.htm#AltMeasure
> 
> )  It took me about 2 hours to just about complete
> it, with the exception of 
> the electronics.  I purchased 2 diodes, both red as
> a light source.  one a 
> 850mcd 1.7v and the other is a 5000mcd 2.4v.  I
> ended up using the 5000mcd, 
> with the top cut off with a drummel.  this seems to
> work good at this point 
> although I have not tested it with a mirror. gona
> make the lap this weekend 
> and start polishing.  Anyways,  I needed a razor for
> the knife edge slide I 
> made, saw the perfect one over the kitchen sink
> sitting in a my stove 
> scraper.  removed it, cleaned it and placed into a
> slide.  It wasn't doing 
> much.  (hmmm wonder what my wife will say when she
> goes to use it? ) once 
> the pitch is poured and the polishing begins I will
> test it.  I am still 
> tossing back and forth on weather to purchase a lap
> mold, or use a piece of 
> wood I have, cut the slits in it and fill them with
> silicon, leaving some at 
> the top, then overlay that with a piece of tightly
> pulled plastic bag or 4 
> ml plastic sheet, once dry pull it from its mold.
> this will give me the same 
> affect as the purchased mold. I can then put this on
> the mirror, and pour my 
> lap onto it and it should work just the same as a
> lap mold sold.  but I am 
> still tossing around the idea.
> 
> "insanity is a fluctuation in the state of mind
> during mirror making"
> 
> charles in wilmington
> 
>
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