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Broken dowel pins ( help!!)

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  • Broken dowel pins ( help!!)

    I've been working on the QC gearbox on my lathe and have discovered a small (yeh right) problem.
    The end of the box has a cover attached with 3 cap screws, and aligned with 1/4"x 1 1/2" hardended dowel pins. These pins are driven into the main gearbox casting into blind holes.
    The last person to have this box apart broke off both of the pins, just above the surface of the box.
    The pins are HARD, a file won't cut them.

    Any ideas on how to get them out?

    I thought about trying to drill with carbide bits, but haven't tried anything yet.


    [This message has been edited by shapeaholic (edited 03-25-2005).]

    [This message has been edited by shapeaholic (edited 03-25-2005).]

  • #2
    Well, the last person to have this box apart was you, just now, so you shouldn't have done that.

    Isn't there enough pin left to align the box?
    I'd be tempted just to tap on the other half of the pin (the recessed half not shown in your pictures) so there's clearance and let the remaining stub that's showing do the aligning. Of course that's the lazy man (me) way.

    Other (better) suggestions can be found below.

    [This message has been edited by vinito (edited 03-25-2005).]


    • #3
      tig a washer on the end and pull them out like a nail after they cool.

      I use to hate working for someone else, now I work for everyone else!


      • #4
        Find a nut that will barely let the pin stub enter the id of the nut, weld the end of the pin to inside of the nut, then try vise grips with a slide hammer attatched. Or if there is still thread left inside the nut, use a bolt to jack it out by putting a short piece of tubbing over the nut, and then inserting the bolt with a washer thru thetubing into the welded on nut.If the tubing is the right length, just tighten the bolt and it will pull the pin out. Adjustments may/will need to be made in the bolt length, and or tubing length.

        There may be enough length left in those pins to just tighten a visegrip on them, and then attatch a slide hammer to the vise grip and hammmer away.


        • #5
          We have had good luck drilling dowels at work out with carbide drills. We drill the dowel until the bit gets through. Then pack the hole with grease. Using a rod that is a sliding fit to the hole you just drilled, insert the rod and tap on the end of the rod with a hammer. This pressurizes the grease and it will flow into the drill point of the hole that the dowel is in. Keep tapping the rod with a hammer and the grease will drive out the rod.

          p.s. Dont type slow around here!

          [This message has been edited by rockrat (edited 03-25-2005).]
          Civil engineers build targets, Mechanical engineers build weapons.


          • #6
            They are only location and the amount sticking out will locate so what's the problem?

            John S.

            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


            • #7
              Are you sure they are broken? I wouldn't be surprised if that is how they are supposed to be. Like John said, they just locate and should be enough there.


              • #8
                Rockrat has the right idea, but don't use grease. Use plumber's putty instead. It's easier to put in the drilled hole and doesn't squirt out like grease will. I have used this idea many times to remove broken 1/4" dowel pins in airplane propeller blades.

                Richard Montgomery
                Robert, LA
                Richard Montgomery
                Robert, LA


                • #9
                  I remove lots of dowel pins for the automotive machine shop so the can surface flywheels and also the dowel pins in the end of crankshafts. I use a piece of flat iron usually 1/4 inch thick and place just below the dowel pin with the iron sticking over the side in the clear and weld it to the dowel pin. after it cools I place a wedge shaped piece of metal with the thin end between the metal and the housing on the inside next to the pin. I then push gently on the wedge while tapping on the part of the iron that is protruding over the side. Each time you tap it the dowel will move out a small bit and the wedge will slide in farther for the next tap. Works very well and is easy, also I break the iron from the dowel pin and it can be ground a little and reused. in your case this may not be an option.

                  Necessity is the mother of Invention


                  • #10
                    Thanks for all the replys!
                    For the moment I figure that I will take the path of least resistance and leave them as is.
                    I'm going to have to replace some of the gears in the box in the near future (ex school machine), and I will try some of these great suggestions then.


                    [This message has been edited by shapeaholic (edited 03-26-2005).]