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Converting Head on BRIDGEPORT TYPE mill.

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  • Converting Head on BRIDGEPORT TYPE mill.

    I know of a mill with drive problems with the vari drive.
    Machine is probably Asian in origin .
    They tried replacing a belt and is short order it destroyed the belt.

    So my question is can the vari head be converted back to step pulleys?
    Or is it not worth doing.
    Also I know where there may be a working Bridgeport vari drive head, It may come with the ram.
    Do they sometimes bolt up to offshore machines or, is there too many differences.

    I am TRYING to remember the name, of the mill in question, might be Alliance or Alliant, not sure?
    Last edited by 754; 11-21-2017, 12:16 PM.

  • #2
    It very well positively might, maybe


    • #3
      Could change to a toothed timing belt style with VFD
      Helder Ferreira
      Setubal, Portugal


      • #4
        Why is it eating up belts? Did the machine do that from day one or only after the drive components became worn? Repair, don't replace.


        • #5
          I went to straight veebelt drive and a vfd on my interact, but because its cnc it makes much more sense, plus the space I have available means the reduction in height was very very welcome. I left the backgear in still, so for slower speeds I use that and the vfd so I dont loose torque low down, and then change to normal drive. The vfd knows what gear its in and reverses the spindle accordingly so "normal rotation" still goes the same direction no matter which gear you are in.

          Have to grin, if you look at the cupboard just behind, you can see the handwheel and other parts from the vari head still "just in case". Hoarders unite
          Last edited by MrFluffy; 11-21-2017, 06:48 AM.


          • #6
            They have replacement kits for the variable speed head. If it has gone unrepaired long enough, the motor shaft is likely to be eaten up. The wear part is a thin plastic bushing on the motor shaft that wears out quickly. The vari drives are kind of noisy even when new. The best permanent fix is to change over to solid timing belt and pulleys and use a VFD. Much easier to work on, quieter and will go for years maintenence free.
            Kansas City area


            • #7
              Bear in mind that the mechanical variable speed drive is giving you more torque at lower rpms.

              A VFD will give you same torque (vector drive or low end boost), or less torque.
              Paul Compton


              • #8
                What kind of shape are the sheave surfaces in??? Rough or grooved surfaces will fray a belt pretty fast. Misalignment could also be a factor although I'm not sure how they could become misaligned unless the bushings are badly worn but then you would hear it.



                • #9
                  If it's a Alliant Mill you can put a BP head on it by changing the gear on the end of the ram I have done this. for parts for a Alliant mill you can get them from Sharp but they cost a bunch some BP parts interchange H&W is a good place to get parts . the motor on a Alliant mill has a hard chromed shaft and the pulley has no bushing in it on the later Alliant and Sharp heads there is a grease fitting on the end of the motor shaft to grease the pulley. Ken


                  • #10
                    Thank Me and others for the info.
                    I did not look the mill over good, he said it was worn and well used.
                    Their extent was to replace belt which it started to shred, so they disconnected it and retired it.
                    I was told it may be bearings
                    At this immediate time , I have a need for a mill, wil, either grab mine with R 8 and put it to use m or get this other one and repair i. It's 40 taper and more HP.