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Thread: modifier on dimensions

  1. #1
    Associate Engineer
    Join Date
    Jul 2015
    Posts
    3

    modifier on dimensions

    Hi all pros... I have a hole A.xxx +/- .005". If I want to control the hole to be on minimum side (A.xxx-.005) if possible, can I modifier MMC ? Vice versa, maximum side, LMC?
    thank you

  2. #2
    Administrator Kelly Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
    Posts
    2,386
    The MMC & LMC modifier define a variable tolerance boundary based on the size of the as-manufactured FOS. These modifiers will will not control the effective as-manufactured size to the minimum size.

    I would first be sure that this is an actual meaningful end item design requirement. By default, a mechanical tolerances of +/- .005 is a range that is assumed to be acceptable for function and fit.

    If this is a absolute requirement one could tighten up the tolerance range where the nominal is the desired size or using +/- 3 sigma as the 6 sigma range define a -3 to 0 sigma as a desired range for the size specification.

    I don't recommend this, BTW.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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