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Thread: Tiny set screws on new pinions

  1. #11
    Join Date
    Dec 2014
    Location
    Durham NC
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    23

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    Those look to be M5 set screws -- 0.96" is a little under 2.5mm -- and a 2.5mm allen key should fit an M5 -- snapping a measurement from the photo you posted seems to agree. I'm not sure why the set screws would have changed from 1/4-20 to M5 -- Although -- I looked up your order from 2017 to get the part number. There is a note on that part that suggests that back in 2012 we had 1/2 pinions bored out to 14mm by our supplier to fit the motors we were using. Since then, it looks like we are purchasing a pinion that comes standard with 14mm bore -- which would likely mean metric set screws. M5 is a fine-thread screw and should be able to take about 5 ftlb of torque vs about 9ftlb for a 1/4-20.

  2. #12
    Join Date
    Oct 2009
    Location
    Elgin Illinois
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    706

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    Thank you Brian for looking into this. Maybe this sound dumb,,,,,,, while I am no machinist, I do have a couple of complete sets of English and metric Allen wrenches, plus a box full of misc. I didn't find any that fit right........ I found loose fits, and just a bit too big fits..... Where as I have a bunch of 1/8" Allen wrenches. Doesn't an M5 set screw boarder on a specialty size?

    I came very close to trying to just tighten these set screws with what I had, as it was late at night and I wasn't thinking well. But then I realized I'd be the one stuck trying to deal with loose set screws. I will drill mine out and end up with a bigger/common sized hole in my pinions.

    Thanks, Chuck
    Chuck Keysor (circa 1956)
    PRT Alpha 60" x 144" (circa 2004)
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  3. #13
    Join Date
    Dec 2014
    Location
    Durham NC
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    23

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    Chuck,

    The M5 x 0.8 is pretty typical in metric stuff -- it is also just about a perfect match to a 10-32 (good thing to remember when you're in a pinch and don't have any metric screws!) -- the socket cap M5 uses a 3mm (almost 1/8") allen -- but the set screw variety uses the 2.5mm (same as the socket cap M4) Most metric allen sets should have a 2.5 so it could be worth another try (maybe some crud on the screw blocking the socket?). Though as others have said--you should have no problem drilling out and re-tapping and M5 hole to 1/4-20 and getting full threads.

    Brian

  4. #14
    Join Date
    Jun 2004
    Location
    Springfield Mo
    Posts
    851

    Default Fine thread

    A "Fine thread tap" is much easier to use for tapping such a shallow hole...

    I think I have thrown my 1/4 20 away....
    The decimal point seems to be the most important on the z axis... x & y not so much....
    ShopBot... Where even the scraps and things you mess up and throw away are cool....

  5. #15
    Join Date
    Oct 2009
    Location
    Elgin Illinois
    Posts
    706

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    Well, as was suggested, it turned out the drilling and tapping of the 4 pinions was not hard. I think I spent a total of 2 hours to do these. But it took 7 days before I started............... I mounted the tap into my drill press chuck, and turned it by hand as Brady suggested. Thanks everyone for your input! Chuck
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    Chuck Keysor (circa 1956)
    PRT Alpha 60" x 144" (circa 2004)
    Columbo 5HP spindle
    Aspire 9.0, Rhino 5

  6. #16
    Join Date
    Mar 2013
    Location
    Memphis TN
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    1,014

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    >> I mounted the tap into my drill press chuck, and turned it by hand as Brady suggested.

    I never thought of doing that. Missed where Brady recommended that. Great idea. I will keep that in the back of my brain for reference.
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