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Thread: Tiny set screws on new pinions

  1. #11
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    21

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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
    Posts
    673

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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)
    Columbo 5HP spindle
    Aspire 9.0, Rhino 5

  3. #13
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    21

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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
    809

    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
    673

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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
    Attached Images Attached Images
    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
    Posts
    691

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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.
    ShopBot Details:
    PRS Alpha 96x60x12
    4hp Spindle
    12" indexer
    Aspire
    Rhino

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