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Re: Pitch Lap Stuck To Mirror

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Posted by Ric/">Ric on November 8, 1999 22:07:22 UTC

: I'm afraid that the only time that I would use the wrap stuff is when making the lap so that the basic form of the mirror is put on the lap. The thickness of the wrap (of any kind) isn't accurate enough to be able to use as an isolator from the lap. Remember that you need a full accurate fit be placed between the lap and the mirror in order to properly figure the mirror. Lumps in one area will cause real problems. An error of 1/4 wave which is 55 millionths of an inch (0.000055") will cause problems and none of the wraps can be trusted to be that accurate for even small pieces. You do need to keep enough water and Cerium Oxide on the lap to keep the two from sticking together. The adding of a drop or two of dishwashing detergent will help in both the sticking problem that happens on occasion and in circulating the Cerium Oxide to the mirror/lap interface.

Of course the wrap can only be used in inital pressing t conform the shape and when cold pressing for a hard lap.Cerium Oxide should be applied when pressing for a figuring session.The cling wrap takes the risk out of the inital pressing,an area that a lot of newbies have a problem with - as in not applying enough fluid onto the surface especially with a soft lap that wonts to stick.

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