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Thread: Question about tolerances

  1. #1
    Associate Engineer
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    Question about tolerances

    I have a cylinder and i have a dimension of 15mm that it purpose is to lead me to a zone that is need to have a ∅220.3, is adequate to have a tolerance dimension on the 15 mm.
    Tolerances cyl.png
    Thank you.

  2. #2
    Administrator Kelly Bramble's Avatar
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    The 15 mm tolerance will be the default defined on the engineering drawing. If there is not a default tolerance you will need one.
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  3. #3
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    I found something on internet:
    A reference dimension is a dimension on an engineering drawing provided for information only. Reference dimensions are provided for a variety of reasons and are often an accumulation of other dimensions that are defined elsewhere (e.g. on the drawing or other related documentation). These dimensions may also be used for convenience to identify a single dimension that is specified elsewhere (e.g. on a different drawing sheet).Reference dimensions are not intended to be used directly to define the geometry of an object. Reference dimensions do not normally govern manufacturing operations (such as machining) in any way and, therefore, do not typically include a dimensional tolerance (though a tolerance may be provided if such information is deemed helpful). Consequently, reference dimensions are also not subject to dimensional inspection under normal circumstances.

  4. #4
    Administrator Kelly Bramble's Avatar
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    Note that according to ASME Y14.5-2009 and previous dimensioning and tolerancing standards reference dimensions are not binding to quality.

    Moreover, reference dimensions are dimensions contained within parentheses.

    See GD&T Definitions
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  5. #5
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    If there is a block on the drawing title with default tolerances (generally based upon number of decimal points in main dimension), if you do not specify a tolerance on your 15mm dimension, the drawing default tolerance will be used for the manufacturing of the item.
    If you need a tolerance smaller than the drawing default tolerance for your 15mm dimension , you must place it with your 15mm dimension.

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