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Thread: Hole Tolerance for Press Fit dowel Pin

  1. #1
    Associate Engineer
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    Mar 2012
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    Hole Tolerance for Press Fit dowel Pin

    Good Morning!
    I'm designing some bolster plates for a project and I need to finish detailing the prints for the vendor to start building them. I have two 16mm diameter dowel pins that are to be press fit into the bolster plate to act as alignment pins into my work piece. the hole tolerance on the bore in the work poece is [16mm H7] so we are having a stainless 16mm dowel press fit into the bolster. My ? is this. What tolerance is correct for the interference fit of the pin and the bolster plate? I'm drafting these in Solidworks and I want to be sure they are dimensioned correctly. I dont fully understand the H7 vs h7? or the other alpha/numeric tolerances for that matter. I havent used GD&T since college and that was almost 15 years ago. I need a little refresher please!
    Thanks!
    Kelley

  2. #2
    Technical Fellow Kelly Bramble's Avatar
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    First, I assume that you have a Machinery's book handy or can borrow. The tolerance grades H7 and h7 will be specified under the standard ANSI B4.1 and ANSI B4.2.

    If the dowel pins are designed to be captured or trapped at final assembly you should be OK with a "Locational Interferance Fit". However, if the dowel pins are not captured and could escape under operation in your assembly you might consider a "Light" or "Force" fit to ensure that the dowel pins does not come out.

  3. #3
    Associate Engineer
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    the intended use of the dowel pins are for a permanent installation as an alignment pin for proper alignment of mold coppers to a bolster plate for machining. the holes in the coppers are a 16mm dia with a H7 fit. they will have to stay in the bolster plates and the wieght of the copper being lowered onto the plate should be enuogh force to set them in the copper. I only used the H7 vs h7 reference because that is the fit of the hole inthe copper. i cannot control that as the holes are already in the coppers, i have to build the plates to machine them. and i want the alignment (dowel) pins to remain in the bolster plate. I had planned on a blind hole set to a depth that would allow the correct amount of pin to stick out of the mold with out "bottoming out" in the holes in the copper
    Last edited by kelley_shreve; 03-29-2012 at 03:09 PM.

  4. #4
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    Bang Head how to decide tolerances for different fits

    Hi Kelly,

    Can you explain how to select tolerances for different fits, with examples.





    Nareen

  5. #5
    Technical Fellow Kelly Bramble's Avatar
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    Quote Originally Posted by nareen View Post
    Hi Kelly,
    Can you explain how to select tolerances for different fits, with examples.
    Nareen

    ? not in two hours or less... I do this in my DFM/DFMA and GD&T classes on request though...

    Here's some handy charts that will help:

    http://www.engineersedge.com/tolerance_chart.htm
    http://www.engineersedge.com/dowel_pin.htm
    http://www.engineersedge.com/general_tolerances.htm

    Videos:

    What is the Right Flatness Tolerance for a Gasket Application

    GD&T Application Single Datum Axis - Two Datum Features

    More..

    GD&T Dimensioning & Tolerancing Videos

    GD&T Training:






    DFM DFMA Training
    Last edited by Kelly Bramble; 04-12-2014 at 09:04 AM.

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