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  1. #1
    angus murray is offline Plastic
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    Default Sizing Roll Pin Holes

    Is there any standard in machinists handbooks for determining the correct drill size in relation to roll pin diameter when drilling the holes? Thanks in advance for any help given.

  2. #2
    register's Avatar
    register is offline Cast Iron
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    I'm not sure of any rule, but making the hole .020" under per inch diameter has always worked for me. Usually I work with roll pins up to .250" dia.

    Just checked MH, and it gives no info on roll pins (at least my 1940s ed.)

  3. #3
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    Roll pins are sized by the diameter of the required hole, i.e. a 1/8" roll pin will fit tightly in a 1/8" hole.

    No calculation required.

    - Leigh

  4. #4
    Troup is offline Titanium
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    Hmmm - my understanding was that the pins were made to fit holes at the standard nominal size, ie the pins are oversize in the relaxed state.

    I checked my Unbrako Sel-Loc literature, and it confirms this.
    The recommended hole size for a 1/4" pin is 0.250 - 0.256"
    for 1/8" pin it's 0.125 - 0.129"

    (PS: while I was writing and checking this, Leigh typed the same thing more succinctly)

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    Quote Originally Posted by Troup View Post
    (PS: while I was writing and checking this, Leigh typed the same thing more succinctly)
    Brevity is the essence of something.

    See, we do agree occasionally.

    - Leigh

  6. #6
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    bosleyjr is offline Diamond
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    "Brevity is the soul of wit"

    Lord Polonius, Hamlet, Wm. Shakespeare

    Glad everyone agrees this time.

    Jim

    This business is well ended.
    My liege, and madam, to expostulate
    What majesty should be, what duty is,
    Why day is day, night night, and time is time,
    Were nothing but to waste night, day and time.
    Therefore, since brevity is the soul of wit,
    And tediousness the limbs and outward flourishes,
    I will be brief: your noble son is mad:
    Mad call I it; for, to define true madness,
    What is't but to be nothing else but mad?
    But let that go.

  7. #7
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    Unhappy for shame

    Quote Originally Posted by bosleyjr View Post
    Lord Polonius, Hamlet, Wm. Shakespeare
    Hmmm...

    That I should elicit a quote from Shakespeare is a shame I shall carry to my grave.

    - Leigh

  8. #8
    PaulM is offline Stainless
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    Leigh has it right, I remember this one clearly from early in my career.

    Pardon the digression;
    I was a ME at a well known co designing a supercomputer. My boss had an outside consultant design the door extrusions. The doors were designed to pivot on roll pins. I had no part in the design and my boss took a vaction when the parts were supposed to come in and had me check on them. Well the consultant undersized the holes - never bothered to look up the design data for roll pins. I figured out the problem and obviously all the prototypes had to be reworked to fit. Somehow the design error became my fault
    Left there within 6 months - they never succeeded in the supercomputer business.

    Paul

  9. #9
    register's Avatar
    register is offline Cast Iron
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    Quote Originally Posted by register View Post
    I'm not sure of any rule, but making the hole .020" under per inch diameter has always worked for me. Usually I work with roll pins up to .250" dia.

    Just checked MH, and it gives no info on roll pins (at least my 1940s ed.)
    You know, I was wondering why it was always so difficult to put roll pins in the undersize holes. I mean, it worked... but it always took some real elbow grease.

    Thanks for the lesson.

  10. #10
    angus murray is offline Plastic
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    Thanks for your reply. I just spent $40.00 on a 5/8 shaft for my DoAll and needed this info before drilling.

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