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  • Dowel Pins

    I'm making a built up crankshaft for a model engine, and wanted to pin the shaft to the throughs.

    I just finished custom making some 0.2535 hardened pins from drill rod for the .252 holes I reamed with my .2490 "under" reamer What gives?

    I drilled the holes 15/64 (crs throughs & drill rod shaft) and reamed .2490. The .2500 pins I bought just fell right in. They measured on the money.

    I reamed about 440 rpm with lots of cutting oil, and cleaned out the chips regularly. My reamers are from an import over/under set. but I've not had a problem with them until now. Am i doing something wrong. or do I just need better reamers(if so, what brand do you have success with)

    By the way, I tried the 1/8 & 3/16 sizes with the same results.

    neonman

  • #2
    Hi neonman,

    I use reamers from L&I (Lavallee & Ide) in Vermont. Online at http://www.lavallee-ide.com/index.html

    Or you can order some from McMaster-Carr at http://www.mcmaster.com They don't sell imports AFAIK.

    Your 440 rpm is ~28.8 sfm, which is about right for a .25 reamer in hardened steel. Feed rate should be .002 to .004 per revolution. Since you're taking a heavy cut, I would suggest a feed of .002.

    The speed and feeds recommendation from the L&I catalog (page 31) are available as a PDF on one of my websites at http://www.AntiqueTechService.com/Im...-2005_pg31.pdf

    And as rkepler noted below, your .0015 interference fit is quite severe.

    ------------------
    Leigh

    [This message has been edited by Leigh (edited 11-14-2005).]
    Leigh
    The entire content of this post is copyright by, and is the sole property of, the author. No assignment
    of title nor right of publication shall ensue from presentation of this material on any computer site.

    Comment


    • #3
      There are a lot of tricks to make a reamer cut a little bit oversize, but none I'm aware of to make it cut .003" over. About the only thing that would be causing that would be either a severely off-center presentation of the reamer to the drilled hole (resulting in a badly tapered hole) or the reamer is cutting large. I'd bet on the latter.

      Have you miked the reamers?

      I do have to comment - .2535 into a .252 hole is quite the press fit, more like a broaching operation for the amount of material being moved. A press fit in that size would less than .0005" over.

      Comment


      • #4
        The link didn't work Leigh. Edit your post to include ".com".

        [This message has been edited by CCWKen (edited 11-14-2005).]

        Comment


        • #5
          <font face="Verdana, Arial" size="2">Originally posted by CCWKen:
          The link didn't work Leigh. Edit your post to include ".com".</font>
          OOOOps Fingers out-ran the brain I usually click on my own links to confirm that they work, but I was in a hurry.

          Thanks for the heads up.

          ------------------
          Leigh
          Leigh
          The entire content of this post is copyright by, and is the sole property of, the author. No assignment
          of title nor right of publication shall ensue from presentation of this material on any computer site.

          Comment


          • #6
            About 1/3 of the chucking reamers I have used American or import ream oversize.I compensate by stoning the sides with a wetstone and reaming test holes until I get the fit I want.
            For critical tolerences I use sprial expanding reamers the only sure way I know other than lapping and gage pins.
            Don't feel bad thou,small holes are much more difficult than larger ones.
            I just need one more tool,just one!

            Comment


            • #7
              Thanks guys, I know the 1 1/2 thou press was a bit stout, but I didn't want the pin comming out.

              I miked the .2490 reamar across each flute, on the ends and in the middle. The end was consistantly .2495, the middle .2490, and the back end, .2485. A bit of a taper, and the wrong way I'd say. Guess I'll shaks loose a few coins and get a few good reamers.


              neonman

              Comment


              • #8
                Thanks guys, I know the 1 1/2 thou press was a bit stout, but I didn't want the pin comming out.

                I miked the .2490 reamar across each flute, on the ends and in the middle. The end was consistantly .2495, the middle .2490, and the back end, .2485. A bit of a taper, and the wrong way I'd say. Guess I'll shaks loose a few coins and get a few good reamers.


                neonman

                Comment


                • #9
                  I also use L&I reamers. As for being over sized, I was going by the instructions of Kozo building my Pennsy A3 switcher live steam locomotive. He recomends to bore the hole first to within .002 then letting the reamer do the rest. I found by doing that my reamers cut oversize, was not leaving enough material for the reamer in my oppinion. Come to think about it, I probably bored the holes too large by accident. Atleast expirience was gained.

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