Re: [ATM] Tilted lap

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

That is a pretty fast slide - half of an inch per
second!

Laps don't have to be perfectly uniform to work fairly
well, in my experience and reading and seeing what
others have done. I would go ahead and use the lap you
have made, for basic polishing. I would also do warm
pressing every so often and use the plastic netting
that citrus fruits, onions, or potatoes come in (with
the label removed, naturally) pressed in between the
mirror and the lap, so as to make tiny little
indentations on the facets. This will tend to make
everything work much, much better. The easiest and
safest way to warm up the lap for this is to immerse
the lap in a bath of rather warm water until you can
easily put a dent into the lap with your thumbnail.
Then you take the lap out of the hot water, put the
netting between the mirro and the lap, and press down
really hard for a few seconds, until you see little
indentations. Then you remove the netting, squirt on
your CeO slurry, and then either cold-press for a
while, or just start polishing.

Whether you do this micro-faceting or not, it is very
important to keep rotating both the lap and the
mirror. There are lots of ways to do this rotation.
Personally, I like to rotate them both the same
direction but by different amounts each time - thus
the one on the bottom goes about 20-30 degrees, and
the one on the top goes maybe 10 - 20 degrees more;
but each one is smoewhat random. But that's just me -
as I said, there are lots and lots of ways of doing
this, and 90% of them turn out fine.

BUT: If you don't rotate, you will definitely cause
astigmatism.

In any case, you will probably end up polishing for 6
to 10 hours, and will probably need to re-pour the lap
before figuring. When you do this, make sure that the
table you pour the new lap on is level.

Good luck.

Guy Brandenburg
> ONE ISSUE:
> The lap is slightly thicker on one side than the
> other, maybe by 2mm.  Easy to tell, because if I
> apply a good amount of CeO solution and set the
> mirror on the lap it begins to slide toward one
> side at maybe 0.5 in/sec. peak velocity.
> 
> Am I headed for a date with astigmatism or some
> other uspeakable horror?  Should I make a new lap?
>  Or should I rest easy, set my work on the spongy,
> non-skid shelf liner pad and go for it? 


=====
Guy  BrandenburgWashington, DChttp://home.earthlink.net/~gfbranden/GFB_Home_Page.html


	
		
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