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Thread: How do I ID a gear to determine its pitch?

  1. #1
    Join Date
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    How do I ID a gear to determine its pitch?

    What is a simple foolproof way of ID'ing the pitch of a pinion?

    Likewise, a spur gear.
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  2. #2
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    Good question... A couple nights ago I spent too long trying to get a nice smooth gear mesh only to figure out I had a 72p spur and 64p pinion.

  3. #3
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    Roll a loose pinion around the circumference of a spur with your finger with a known 64p and 72p pinion/spur set.

    Then run the pinion in question over the same spurs. Your finger will feel a difference if it is not the correct pitch. It will feel a lot less smoother.
    Last edited by Overdrive; 09-05-2016 at 02:32 PM. Reason: added info

  4. #4
    Join Date
    Aug 2016
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    7
    Or ......

    Roll the gear pressing firmly on thin stack of paper or balsa wood and count the # of impressions in 1 inch.

    Caveat - it's not 'fool prof' as fools are so ingenious.

  5. #5
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    Quote Originally Posted by Frankie View Post
    Good question... A couple nights ago I spent too long trying to get a nice smooth gear mesh only to figure out I had a 72p spur and 64p pinion.
    And that is exactly what happened to me

    Surely there is a caliper measurement test or an available chart that resolves this issue?
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  6. #6
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    Quote Originally Posted by Overdrive View Post
    Roll a loose pinion around the circumference of a spur with your finger with a known 64p and 72p pinion/spur set.

    Then run the pinion in question over the same spurs. Your finger will feel a difference if it is not the correct pitch. It will feel a lot less smoother.
    Thank you sir, that does work. I also wore my jewelers glasses thingy and you can see when it's wrong when rolling them with your fingers also. Now I know.. Thanks again.

  7. #7
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    Or you could buy one of these, I did. If a gear fits one of the holes, but has more teeth then the hole is marked for its 72p

    http://www.ebay.com/itm/331958378718...%3AMEBIDX%3AIT

  8. #8
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    What a great concept. I wonder if they make one for 72 pitch gears
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  9. #9
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    I checked yesterday, just 48p and 64p for now.

  10. #10
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    Will not work with those gears that used the same OD with altered tooth forms for different tooth counts.
    l.d. kelley, M.A. Ramcatlarry@aol.com

    60 year pin 1959-2019
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  11. #11
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    Haven't posted in a year I think,
    ASME (American Society Mechanical Engineers) Gear Standards:
    Pitch Dia. = # teeth/Pitch, 12/48, 12/64, 12/72 etc.
    For this discussion, Diameter is APPROXIMATED at 1/2 tooth height, so use Diameter = Gear O.D - 1 Tooth height
    Diameter @ 1/2 tooth height = (# of teeth)/Pitch.
    Diameter = (# of teeth)/Pitch. = Gear O.D - 1 Tooth height
    12t > 48P 12/48= 0.25" Dia + 1 tooth height = Gear O.D.
    12t > 64P 12/64= 0.188" Dia + 1 tooth height = Gear O.D.
    12t > 72P 12/72= 0.167" Dia. + 1 tooth height = Gear O.D.
    1) This assumes manuf. adheres to ASME standards
    2) Ditto Ramcat above

    Hope that helps MIT DER GearsSprokenn
    Last edited by MentalKase; 10-18-2016 at 09:59 PM.
    Guy Middleton
    Everything I was taught in Engineering school I had already learned from slot cars....

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