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GD&T Question

How do I use the basic [4.39] with total run-out or do I somehow add it with the concentricity? I am lost with how to measure the 4.39". I can do it with a true position but that is not an option here.


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  • Your 4.39 BASIC is tied back to the right hand side, where there is no datum. As already stated here, unless there is something stated in a note or on the print elsewhere, that basic dim should be connected to a datum feature with a corresponding geometric control somewhere on the print. The statement that you were given "Basic dimensions can be used..." is an attempt to circumvent the issue that this print is incomplete as we have been presented it here.

    As kingsld says, there is also nothing wrong with enhancing your GD&T knowledge on company time.
  • Zero,
    BASIC dimensions almost always correlate back to a feature control frame....so things like "profile", "position",and "runout" are directly related to BASICS if the engineer knows what he/she is doing....rough example FEATURE CONTROL FRAME: POS|Ø.015|A ....this roughly correlates to ±.0053 So if you have a basic relating to a specific feature connecting any 2 axis' the tolerance on both would roughly be ±.0053..this works for hole locations....profile if it is bilateral...example profile( bilateral) of .020 ....means ±.010 ....runout is found using dial indicator usually ......when checking runout the most accurate way is with a dial indicator with proper graduations...i.e.; .001 or .0005, or .0001...etc....