Re: [ATM] Mirror stuck on pitch lap

["Jerry" <wa4guu@verizon.net>]

I haven't tried the freezer for this sort of thing.  I think that might
separate the pitch from the tool also.

I have never had an 8 inch that I could not separate in 30 minutes or so. So
easy that I don't even consider this to be a problem.  What I am not sure of
is in the case of cast tools. I have always used glass or marble for lap
bases. But if you have hit it with a hammer with no damage then this should
not hurt it either.

I use a 12 inch carpenter clamp for an 8inch. Keep it wet (the mirror and
lap, not the clamp). If it has dried soak for a few hours. Put a block of
wood against the edge of the tool and one against the opposite edge of the
mirror and tighten the clamp as tight as you can get it. You can work it
back and forth. Several minutes pushing one way and then take the clamp off
and set the blocks and clamp to push the mirror the other way. Do that even
if you see no movement.  It may take a few iterations to get any movement at
all.  Once it has moved even slightly it will get easier. Listen. You will
hear something like tapping or thumping when it starts slipping and you
tighten the clamp to keep it moving. Spray some water around the edge to
keep it wet and you can reverse direction after it has move a little in one
direction. A little back and forth and it will loosen up to where you can
move it by hand. 

Even if there is bare pitch in contact with the mirror in a few places, if
it is mostly coated with polishing agent it will probably separate from the
mirror before separating from the tool. 

Of course any method that you can apply high force to push the disks
laterally relative to each other will work. The carpenter clamp is
relatively safe because you will be hard pressed (pun) to put so much force
as to break a disk.  A bottle jack might work but you might not be able to
limit the force within a safe range.

When separated you will still have a lap. Channel it, put some polishing
agent on it and press.

Jerry

Jerry



-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Francis J. O'Reilly
Sent: Sunday, February 04, 2007 8:16 PM
To: atm@atmlist.net
Cc: mirrorworkshop@mtbparker.com
Subject: [ATM] Mirror stuck on pitch lap


Guys and ladies,

I poured a pitch lap today (Gugolz 64) and while hot pressing with cerium
on the mirror, it became stuck to the pitch lap. I have tried putting the
entire project in the freezer for a couple of hours to unstick them, to no
avail. I tried the bigger hammer method by knocking on the dental stone
tool with a hammer shielded by a piece of wood, no luck.

Any suggestions?

Francis J. O'Reilly


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