123 block-lapping

i was looking at buying a set of 123 blocks and came across a spec. which i don't understand "up to .0003 over allowance for nominal lapping"
could someone explain? thanks!
rtv
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They give you up to 3 tenths extra meat for when you lap them on a belt sander.

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On Tue, 27 Apr 2004 18:59:53 GMT, "Tom Gardner"

Yeah, break out the old 80 grit belts and...
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For toolmakes who want their 123 blocks to 4 decimals they can finish lap the blocks themselves. Of course most shops don't even have a lapping plate available, but a granite table and some lapping film taped to it might work (not sandpaper, it's not flat enough). A cast iron plate and some diamond paste does a really nice job, shiney enought to shave in :-)
rtv wrote:

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James P Crombie
Slemon Park, PEI
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