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  • shaft extension

    How do you guys usually extend a shaft when you need to. I have to
    change out a motor on a mill I am working on, and the shaft on the bad
    motor is like 6" long to go through the very thick step pulley. The shaft on
    all the motors I am considering is much shorter.

    Im thinking I am going to have to conical shape the ends a bit, weld it up,
    then turn it down. Am worried about the hardness of the weld though.

    Suggestions ?
    John Titor, when are you.

  • #2
    I did the same thing with 2 ton electric hoist that had a 3 phase motor on it and I put a single phase on it without a problem. Check to see if you can press the shaft out of the armature on the new motor and make a new one. I did a 100% weld on the shaft.

    Comment


    • #3
      Hi,

      Depends on how much of a load is placed on the motor. I have welded a few up with extentions and done shrink fits. But I mostly prefer a simple key and set screw if possible.

      Dalee
      If you think you understand what is going on, you haven't been paying attention.

      Comment


      • #4
        Drill a hole in one end of shaft A, then turn shaft B to fit snuggly into the hole of shaft A.
        Next, mill a slot across Shaft A, to centerline.
        On Shaft B, mill it down to centerline as well.
        They will now slide together and 'Lock'.
        A little weld will make it permanent.
        It might not be feasible with a short motor shaft, but it might give you an idea.
        This is a trick I was shown by an old-timer to make drills longer.
        I apologize for my awful drawing.
        -
        Last edited by KiddZimaHater; 11-10-2013, 08:05 PM.

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        • #5
          Oh yea .. I have heard about pressing the shaft out of an armature, I have a good press
          so I might check that out. But I like Haters idea too .. it has that thinking outside the
          box feel.

          Also I forgot to mention that I have to go from a 5/8 shaft to a 3/4 shaft ..

          On a shaft that has a sleeve on the end to go from 5/8 to 3/4, is there enough meat
          to have structural integrity ?

          Thanks
          Mike
          Last edited by Mike Amick; 11-10-2013, 10:47 PM.
          John Titor, when are you.

          Comment


          • #6
            Any chance of boring at least part way through the step pulley to allow a larger shaft at that point- would give the option of pressing that end of the shaft over the existing shaft. Should be enough meat there.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #7
              If the shaft is plain old S355 and not some highly alloyed, the welding isn't going to harden it. Every weld I've machined has been soft as peanut butter in the lathe, the only issue being some interrupted cutting as the weld is not symmetrical or round.
              Amount of experience is in direct proportion to the value of broken equipment.

              Comment


              • #8
                John Stevenson has repaired many motor shafts by building uo with weld, I don't know if he extended any but I'm sure his expertise on this matter would be very helpful to you.
                MBB

                Comment


                • #9
                  Originally posted by mikeamick View Post
                  Also I forgot to mention that I have to go from a 5/8 shaft to a 3/4 shaft ..
                  Reduce the diameter of the 5/8 part, bore the 3/4 part, and heat shrink the two together.

                  Comment


                  • #10
                    Originally posted by malbenbut View Post
                    John Stevenson has repaired many motor shafts by building uo with weld, I don't know if he extended any but I'm sure his expertise on this matter would be very helpful to you.
                    MBB
                    Two for me so far. One for the BP clone, the other for a Denford Easymill.
                    Paul Compton
                    www.morini-mania.co.uk
                    http://www.youtube.com/user/EVguru

                    Comment


                    • #11
                      KiddZima,
                      The method you have illustrated is creative and pretty cool
                      but for all the effort and really not having much strength
                      I am not sure I would do it. You do not want to take away
                      any "meat" from the origional shaft if possible. I believe a
                      plain old way of turning a generous chamfer (weld prep)
                      on both the motor and the extension shafts, and welding
                      them makes the most sense. Use a extension shaft that
                      is 1/8 to 1/4 inch larger than the motor shaft for cleanup
                      room of course.
                      The method you have shown might be good if you are wanting
                      to use silver solder or braze. In that it might be the hot ticket.

                      --Dooer
                      DZER

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                      • #12
                        Another method worth considering if you can do it well:

                        Many years ago the 2 horse motor on my Sears compressor broke. The stress on the serpentine-style belt sheared the shaft off just to the inside of the bearing. It was an expensive motor, so I took it to a local old fellow who did stuff, and he machined a very tight sleeve to go over the stub, then pressed a new piece of shaft into it. It came loose the first time, so I took it back and he did it again, and the repair this time has lasted for about 20 years.

                        The old fellow celebrated his 90th birthday recently. He's still fixing stuff.

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                        • #13
                          Originally posted by bruto View Post
                          ..so I took it to a local old fellow who did stuff............
                          Ha ha! I hope someone says that about me one day!

                          Comment


                          • #14
                            If your new motor has the shaft extending out of both ends, perhaps you can just use the press to move it so more sticks out the end for your pulley.
                            Paul A.
                            SE Texas

                            Make it fit.
                            You can't win and there IS a penalty for trying!

                            Comment


                            • #15
                              Originally posted by Jaakko Fagerlund View Post
                              If the shaft is plain old S355 and not some highly alloyed, the welding isn't going to harden it. Every weld I've machined has been soft as peanut butter in the lathe, the only issue being some interrupted cutting as the weld is not symmetrical or round.
                              Ok .. interesting. I welded up an old vice and tried to mill the weld smooth. Broke a bunch
                              of EM's I always thought it was the weld it self that was hard (mig welding) I am way not
                              afraid to give it a try on the shaft though ..

                              Originally posted by jlevie View Post
                              Reduce the diameter of the 5/8 part, bore the 3/4 part, and heat shrink the two together.
                              Thats why I come here .. lol Can't believe that thought didn't come to me. Just steal a
                              little meat from the smaller shaft help the integrity.

                              Ok .. I think I am going to go what appears to be the traditional route. I'll weld prep the
                              shafts and weld. Also .. as per the great suggestion, I will use a shaft that is larger than
                              needed so I can straighten and smooth.

                              Thanks
                              Mike
                              John Titor, when are you.

                              Comment

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