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Thread: Formula and Label Classification Questions

  1. #1
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    Question Formula and Label Classification Questions

    Regarding: https://www.engineersedge.com/calcul...tolerances.htm


    You have the a [Clearance] [Interference] values (min and max values) which is different from your hole tolerances.


    That I'm trying to apply this to a linear running fit thats RC5 or RC6 rather than a radial fit. [1] Do I need to halve the tolerances because its radial and [2] which tolerances/clearance values do I want to use?


    My application is similar to a plug and socket. Except that I want a looser running fit than what you normally want a socket to grab with.

    Lastly, is this calculator for steel at 20C?

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    Administrator Kelly_Bramble's Avatar
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    Those tolerance fits are per. ANSI B4.1 which I think are based on standard room temps 20C or 68F.

    Those tolerances are on a diameter fit so I support for a fit of a feature based on radius one would half the number to achieve the same fit - as which a profile of surface tolerance. Though for a fit to exist there must be an opposite surface of reference which circles you back to using the tolerance variations as a feature of size or diameter.
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    Quote Originally Posted by Kelly Bramble View Post
    Those tolerance fits are per. ANSI B4.1 which I think are based on standard room temps 20C or 68F.

    Those tolerances are on a diameter fit so I support for a fit of a feature based on radius one would half the number to achieve the same fit - as which a profile of surface tolerance. Though for a fit to exist there must be an opposite surface of reference which circles you back to using the tolerance variations as a feature of size or diameter.
    Thank you K Bramble!,

    Using the absolute tolerance, that lets me derive the other component’s nominal sizing. I have adjustability baked into the geometry which helps define the exact fit sliding that I'm seeking.


    General Question: Why is there a clearance value for a hole and cylinder arrangement. Isnt the tolerance your specified fit of your nominal hole size vs the nominal cylinder part?


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    Administrator Kelly_Bramble's Avatar
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    Quote Originally Posted by JL-Designs View Post
    General Question: Why is there a clearance value for a hole and cylinder arrangement. Isnt the tolerance your specified fit of your nominal hole size vs the nominal cylinder part?
    I think I know what you're asking... let's see what happens.

    Expressing size as a nominal with +/- tolerances is an option for expressing tolerances but not required. There are many acceptable methods to express size and tolerances with respect to ANSI or ASME dimensioning and tolerancing standards.

    ANSI B4.1 specifies a required end item fit based on functional requirements. An RC6 is a Running Clearance fit based on a range for a given nominal size. The fits provided are intended for plain (non threaded) cylindrical parts and B4.1 makes recommendations on preferred sizes, allowances, tolerances, and fits for use wherever they are applicable.

    I believe the fits are based on Experimental work long ago.

    For a given size, e.g. RC6, Dia. 1.25 nominal size the desired MMC and LMC are provided for the hole and mating shaft feature. Also note that for the size given for the shaft feature is a double negative tolerance.

    Tolerances may be expressed using a variety of methods, including double negatives however I don't recommend that.

    In the default example given by the calculator, the hole could expressed as Dia. 1.2500 + .0025 / - .0000 and the shaft feature could be expressed as Dia. 1.2500 -.0020 / -.0036 (two negative tolerances with respect to the nominal).

    In practice we ~ might actually use:

    Hole: Dia. 1.2500 + .0025 / - .0000 (H9 Tolerance)
    Shaft: Dia 1.2480 + .0000 / - .0016 (e8 Tolerance)

    Clearance between the shaft and hole range between .00610 and .0020 depending on as-builts.
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    Quote Originally Posted by Kelly Bramble View Post
    I think I know what you're asking... let's see what happens.

    Expressing size as a nominal with +/- tolerances is an option for expressing tolerances but not required. There are many acceptable methods to express size and tolerances with respect to ANSI or ASME dimensioning and tolerancing standards.

    ANSI B4.1 specifies a required end item fit based on functional requirements. An RC6 is a Running Clearance fit based on a range for a given nominal size. The fits provided are intended for plain (non threaded) cylindrical parts and B4.1 makes recommendations on preferred sizes, allowances, tolerances, and fits for use wherever they are applicable.

    I believe the fits are based on Experimental work long ago.

    For a given size, e.g. RC6, Dia. 1.25 nominal size the desired MMC and LMC are provided for the hole and mating shaft feature. Also note that for the size given for the shaft feature is a double negative tolerance.

    Tolerances may be expressed using a variety of methods, including double negatives however I don't recommend that.

    In the default example given by the calculator, the hole could expressed as Dia. 1.2500 + .0025 / - .0000 and the shaft feature could be expressed as Dia. 1.2500 -.0020 / -.0036 (two negative tolerances with respect to the nominal).

    In practice we ~ might actually use:

    Hole: Dia. 1.2500 + .0025 / - .0000 (H9 Tolerance)
    Shaft: Dia 1.2480 + .0000 / - .0016 (e8 Tolerance)

    Clearance between the shaft and hole range between .00610 and .0020 depending on as-builts.
    So assuming my material could be cut and grind stock exactly, that I had infinite resolution for tooling, the Clearance range alone defines the fit. That a RC6, for one side, is [0.0020/2", 0.00610/2"]?

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    Administrator Kelly_Bramble's Avatar
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    Quote Originally Posted by JL-Designs View Post
    So assuming my material could be cut and grind stock exactly, that I had infinite resolution for tooling, the Clearance range alone defines the fit. That a RC6, for one side, is [0.0020/2", 0.00610/2"]?
    Yes, I would agree with that statement... adding for that nominal size range.
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    Quote Originally Posted by Kelly Bramble View Post
    Yes, I would agree with that statement... adding for that nominal size range.
    Thank you! You have been most helpful!

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