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7/8" motor shaft, 16mm pulley bore. What do to?

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  • #16
    The problem with modifying the motor is not the process (that's easy), but that you are dooming yourself to having to do that again when you replace the motor. Motor sizes go with certain shaft sizes.

    Making a "special" once means that there is likely no other motor which you can find that will fit without modifying it. Now, next time you need to replace the motor (they do fail), you will not have a lathe (dead motor) and will need to modify the shaft or pulley again.

    Using standard stuff whenever you can means less trouble in the long run.
    CNC machines only go through the motions.

    Ideas expressed may be mine, or from anyone else in the universe.
    Not responsible for clerical errors. Or those made by lay people either.
    Number formats and units may be chosen at random depending on what day it is.
    I reserve the right to use a number system with any integer base without prior notice.
    Generalizations are understood to be "often" true, but not true in every case.

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    • #17
      Another perspective is design and maintenance.
      On one of my lathes, it has an 8hp motor.
      I had to take it apart because a mouse had gotten
      inside and I wanted to check the windings for
      mouse damage. Dreadful creatures.
      Anyhow, I had to take the pulley off the motor shaft.
      It was a 5 belt pulley and the shaft was 1-3/8" with
      a key. Pulley was a standard affair, secured with
      a set screw.
      Well let me tell you, I had a 15 ton 3 jaw puller and
      I worked my azz off to remove that pulley from the
      motor shaft. The puller alone would not take it.
      I had the oxygen acetylene torch applying heat to
      the pulley, bring it to a dullest red. I would heat and
      then turn the wrench on the puller, then hit on the
      puller screw with my 3 pound copper hammer to get
      the pulley to move. I made head way about 30 thou
      at a time. It took 2 hours and a bunch of acetylene
      to get that pulley off. I might have been better using
      an impact wrench on the puller screw, but I think that
      might border on tool abuse. It was an Enerpac puller
      but I don't think the screw was all that hard. So I kept
      with the hand wrenching and applying molly lube to
      the puller screw threads.
      Anyhow, I was successful getting the pulley off the
      motor shaft. Plenty of that red fretting corrosion.
      Set screws and keys are a miserable way to attach
      hubs to shafting. Not wanting to fight that battle
      ever again, I bought a QD (quick disconnect) taper
      lock bushing type pulley. QD bushings bolt in and
      bolts also drive them apart for easy withdrawal.
      While I was at it, I got a little larger pulley to increase
      the speed of my lathe. I think I want from 850 to 1200
      RPM top gear speed.
      No I am not worried about the belts slipping,
      No I am not worried about the headstock exploding
      No I am not worried about the bearings melting
      No I am not worried about the chuck falling off.
      So yes the mouse had chewed some of the fishing line
      that ties the coil wraps. I also took the opportunity to
      clean the inside of the motor (filthy) and I bought some
      Glyptal to paint the windings up pretty. I put some
      shrink tube on the leads to make sure I would have
      no shorts. I washed out and re-packed the bearings
      with synthetic grease and painted the motor since it
      was now clean.
      But yes, the QD taper lock pulleys are the way to go.
      Easy on and easy off. I think I paid a little over $200
      for the pulley and bushing, only so expensive because
      it was a 5 belt pulley. But in my mind, money well spent
      to avoid ever having the fretting happen again, or the
      other extreme, having it not stay tight on the shaft.
      Best of luck.

      -Doozer

      DZER

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      • #18
        Doozer, yes it was Browning Taper Lock we used... never had an issue even without a keyway.
        Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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        • #19
          The November/December 2011 issue of HSM has an article about pulley hub repair/replacement.

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          • #20
            The 3/4" compromise looks interesting. Also, you may be able to get a pulley pair which has a slightly bigger diameter with the larger hole, as long as there is room in the casing. There is no substitute for having gears/belts for speed control, don't get lazy like many VFD users who would prefer to spend money rather than bother to change speed manually. Having the bigger motor and being prepared to actually change speeds manually is a bonus adding versatility.
            When I changed the Tom Senior Light Vertical mill from MT2 to R8, I changed the motor from a 1/2hp to a 1hp with a VFD, running from 25-75Hz, the 4 speeds by belt are still essential for a good spread of speed and torque.
            Last edited by old mart; 09-01-2022, 03:44 PM.

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            • #21
              So there are several votes for Option Δ, make a new pulley. I like it. I'm pretty sure I can simply copy the principal dimensions from the original, but not cut the V-groove so deep. On the original pulley, the inside of the belt clears the bottom of the groove by .15", so I can leave quite a bit at the bottom of the groove in the new one, have plenty of wall thickness between the groove and the bore, and still be sure the belt doesn't bottom out. Taper-lock hubs are cool, I've encountered them before, but for my purposes I'm sure a conventional key and setscrew will plenty adequate. I guess I'll be calling my local Metal Supermarket for a hunk o' stock. (Unless one of you has a 2" length of 3.5" Ø steel you want to send me.) The original is cast iron, so I'd be inclined to use steel for a new one, but aluminum would be suitable as well, don't you think? It may depend on what I find in the remnant racks. Thanks, guys. That's what I came here for.

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              • #22
                Big mistake not making the V belt grooves as wide and deep as the OEM, but heck you've discarded a lot of excellent ideas already so go for it.
                Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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                • #23
                  Originally posted by Bob Engelhardt View Post
                  About the power: the OP is not expecting to use the 1-1/2hp, rather to get better power at reduced frequency. Where his current 3/4hp might fall to an unusable 3/8 at some frequency, a 1-1/2 falling to 3/4 & all be well.
                  Exactly. As another Jet 1024 owner I figured you'd understand my aim. As for overpowering the machine, I don't think so. Most references to this class of lathe that I've seen show a 1 or 1.5 HP motor. And while I'll probably never call on it to provide that much, I don't think it's inappropriate. The 1024 is a pretty stout little machine.

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                  • #24
                    Originally posted by wmgeorge View Post
                    Big mistake not making the V belt grooves as wide and deep as the OEM, but heck you've discarded a lot of excellent ideas already so go for it.
                    Seem to me, as long as there' s clearance under the belt, such that only its flanks contact the pulley, that's all you need.

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                    • #25
                      Belts 'wear in' to some degree. I'm sure you could reduce the clearance, but deciding how much might be difficult.
                      Southwest Utah

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                      • #26
                        Originally posted by Randy View Post

                        Seem to me, as long as there' s clearance under the belt, such that only its flanks contact the pulley, that's all you need.

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                        Belt pulleys are made the way they are for a reason....and to account for wear and transfer power.
                        Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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                        • #27
                          Yes, wear will gradually reduce the gap, but providing there is a gap, the drive will work just fine. OK, it might mean changing the belt more often say every 2 years instead of every 5 years, but thats not a big price to pay is it?
                          'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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