Used Granite surface plate chipped.
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  1. #1
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    Default Used Granite surface plate chipped.

    Hey all, I might be getting a used surface plate for nearly free, 36x36 4” or 6” thick pink granite (not sure of manufacture).
    The top corner has roughly 1” by 1” chip that is in the work area (top).

    I’m personally not affected by the damage but would like to get it lapped one day.

    assuming no structural cracking/damage, is this chip a big problem on lapping? I would assume the chip would nullify any possibility of a certification after lapping?

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    Quote Originally Posted by Homebrewblob View Post
    Hey all, I might be getting a used surface plate for nearly free, 36x36 4” or 6” thick pink granite (not sure of manufacture).
    The top corner has roughly 1” by 1” chip that is in the work area (top).

    I’m personally not affected by the damage but would like to get it lapped one day.

    assuming no structural cracking/damage, is this chip a big problem on lapping? I would assume the chip would nullify any possibility of a certification after lapping?
    Wont present any problem for it being lapped, wont be a problem in use unless your sub inch part/setup falls into the hole .
    Getting a sticker on it might be a problem, wont cost anything to ring the guys and ask, perhaps they could advise on some special goo to fill chip with before its lapped. I'd have thought as long as the repeat reading over the repaired area comes in it should be certable , do you need the sticker or just wanna know how flat it is?

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    I just wanted to know how flat it would be
    But it made me curious as to how you would certify it with a chip missing.

    If all lines up I’m planning to eventually have it lapped and start using it to learn scraping machine ways/parts.

    Part of my plans of Grandeur!

    But we’ll see how all goes.

    I thought I’d ask the forum, Thanks brother

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    You might like this if youve not already been here, a quick video following a clearly very experienced tech doing his thing. Lots of between the lines tips here from using one mirror to using the repeat meter as a transfer gauge for flatness as well as local reading, probably more besides.

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    I am not sure, but once upon a time I worked in a shop that had a 4' x 8' plate with a sizable chunk broken off the corner. It was never certified or anything to my knowledge, but never got a part rejected we checked on it either (blanchard grinding larger plates)....

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    If the chip is in the corner and not in the middle, it will make no difference at all to lapping or certification. Indeed, the Federal spec GGG-P-463c, says that the working area for that size plate starts at 1.5" in from the edges.

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  11. #7
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    FWIW I have an 18 X 24" plate with a large corner broken off and glued back on. I bought it at an auction long ago, when I did it had a current calibration tag on it.


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