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Motor for a RF 31 mill drill?

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  • Motor for a RF 31 mill drill?

    I bought a used RF-31 mill drill! My first mill..Have yet to pick it up..

    Anyways the machine has a 3 phase motor.(came from a garage that had some other 3 phase machines as well).The guy had a phase converter hooked up that Im getting as well..A rotary phase converter I guess,a big old motor, when he ran the mill the converter was super noisy, and had all kinds of electrical boxes etc that Id rather not deal with..

    So would it be hard to find or expensive to aqcuire a normal single phase motor for this machine?

    Is the 3 phase motor setup better in anyway,should I just keep that?

  • #2
    Get a VFD. It will run your 3 phase motor from single phase power and turn it into a variable speed motor.

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    • #3
      +1 on the VFD. A 240V 1ph to 3ph converter is around $150 on ebay.

      The end result will be a smoother running motor that can run from a few hundred RPM to full speed. Add the normal pulleys to that and you have a much more versatile machine.

      I just did this change to my mill and I'm quite happy with the result.

      Dan
      At the end of the project, there is a profound difference between spare parts and extra parts.

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      • #4
        I agree on the VFD - they are fantastic additions to a machine...

        But, to answer the question about replacing the motor with single phase - the mill-drill has a pretty forgiving means of mounting a motor, allowing adaption to several of the different mounts/types of motors. If youve got a couple old motors off past equip laying around the shop (like most of us do) possibly one of them will adapt/fit up to it.
        If everything seems to be going well, you have obviously overlooked something........

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        • #5
          How about single phase and DC

          Consider using DC.

          Recently I replaced the 3 phase motors on my mill with DC motors. Yes, motors. My old Index uses two, one for the spindle and one for the table feed. The cost of DC conversion (per motor) was about the same as purchasing a new single phase AC motor. I was able to locate new industrial (Leeson) DC motors and purchase used KB Electronics controllers on Ebay. I chose the KB controllers on the advice of Forum members here. I can't be happier with the outcome! The motors are quiet and have plenty of power in all speed ranges. One motor is 180 volt and requires 240 volts for the controller, the other 90 volt, requiring 120 volts for the controller. Wiring was simple, they are reversible and speed is changed with a twist of a knob.

          Three phase may have some advantages but since I haven't used it I can't speak about that. After following this forum for a number of years I will say that it seems that those with 3 phase converters seem to have trouble with them from time to time. I guess that could certainly happen with DC systems as well but I haven't read much about DC trouble after it was up and running.

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          • #6
            I have an ancient RF-31. It has a 2hp three-phase 2 speed motor with the 4 pulley setup. It had a static converter which I replaced with a cheap TECO VFD, and wired direct to the motor in the high speed setting. I added a remote control box with speed pot, start/stop/direction switches. I routinely run it from 30hz to 90hz.

            I am currently converting my lathes to 3phase with VFD. IOW- I love it.

            allan

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            • #7
              Another vote for the VFD.
              You are fortunate to already have the 3 PH motor, count it as a bonus. If you are going to be spending money anyway to get the mill running may as well spend it on a VFD. Soo much nicer, it's the way a lathe or mill should be equipped from the factory.
              Home, down in the valley behind the Red Angus
              Bad Decisions Make Good Stories​

              Location: British Columbia

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              • #8
                I had a 3-phase RF-31, and like the others suggest, put a VFD on it. It was very nice to not have to change pulleys.

                The 3-phase motor is going to be smoother running too.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  Originally posted by lazlo
                  I had a 3-phase RF-31, and like the others suggest, put a VFD on it. It was very nice to not have to change pulleys.

                  The 3-phase motor is going to be smoother running too.
                  Yep, I agree about using a 3 phase motor - I even took the single phase motor that came with mine off, so I could use a VFD on it....

                  However, if you are dead set on going to single phase, drop me a PM and I will be happy to sell the original single phase 2HP motor...... from Taiwan, BTW, instead of China.
                  TexasTurnado

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                  • #10
                    This VFD/adjustable speed actually sounds pretty nice..Will probably keep the 3 phase motor since this is the case..Only thing I didn't like initially is the rotary phase converter motor, it was super loud when he ran the thing (Id like to run it in the middle of the night when everyone is asleep)...

                    On a side note any idea as to how much the individual pieces of these rf 31s weigh?Pretty dead set on breaking the thing down into a few pieces so I can just carry them down my basement steps,probably with the help of a buddy, if needed..

                    Also Its a "birmingham" brand RF 31 anyone know if these are these chinese or taiwanese made?Looked all around the web but not much info

                    Thanks

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                    • #11
                      Originally posted by ak95xj
                      On a side note any idea as to how much the individual pieces of these rf 31s weigh?Pretty dead set on breaking the thing down into a few pieces so I can just carry them down my basement steps,probably with the help of a buddy, if needed..
                      About 600 lbs. Has an awkward center of gravity, if you lift the whole unit with a sling. The head slides right off the column, and you can unbolt the column from the base, if you need.

                      Also Its a "birmingham" brand RF 31 anyone know if these are these chinese or taiwanese made?Looked all around the web but not much info
                      Mine was Taiwanese, and had turned aluminum pulleys. The Harbor Freight models have rough-cast pulleys. YMM.
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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