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  • Machine Tapping on a Jet JMD-18

    I'm trying again, since I got no answer before.

    Can I use a reversing switch on this machine?

    If so, how?

  • #2
    We need more information. Is your machine single or three phase? If single phase, is the motor two speed?

    My guess is that it is a two speed motor, and is not reversable since most milling machines are reversable from the factory if possible. If it is single phase, even if reversing were possible, it would not be instantaneous.

    If you anticipate the need for power tapping, your best investment would be a tapping head.
    Jim H.

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    • #3
      It is a single phase 230 volt only motor.

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      • #4
        Originally posted by JCHannum
        If you anticipate the need for power tapping, your best investment would be a tapping head.
        Is that pretty much the primary reason for reverse on a mil? I've wondered since all the cutter go the same way! I have reverse on my rung foo.
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        • #5
          Originally posted by ligito
          It is a single phase 230 volt only motor.
          Is the motor two speed, or single speed?

          If it is single speed, a drum switch can be installed. However, even with that, you will not get instantaneous reversing, but will have to wait for the motor to stop before it will change direction.

          Milling machines are usually supplied reversable, but not for the express purpose of tapping.

          There are right and left hand ground end mills available. Also, when using plain milling cutters, boring heads and slitting and slotting saws, it is often advantageous to be able to run the machine in reverse.

          The boring head is very handy for OD turning of shapes that cannot be easily handled in the lathe. When used for this purpose, it is run in reverse using a standard boring bar.
          Jim H.

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          • #6
            Originally posted by Your Old Dog
            I've wondered since all the cutter go the same way! .
            WOOPS! A big negative on that. I have used cutters that cut the "other"
            way.

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            • #7
              As far as I know, single phase motors are incapable of "plug reversing" or instant reversing the way 3-phase motors are. Single phase motors must be allowed to coast to a complete stop before restarting in the opposite direction. Because of this, I would not want to try and tap directly with a single phase machine. That is why it was reccommended to use a "tapping head". The tapping heads made by Tapmatic uses a gear reduction head (to slow spindle speed and provide for reverse rotation) with a floating tap spindle out the bottom. There is a collet arrangement that typically use a rubber & steel collet made by Jacobs. These collets can handle several different tap shank diameters, depending on the exact size of the collet. Probably 3 (or maybe even 2) collets could handle every tap that the head is capable of driving. You can drive a tapping head with a mill or even a drill press. When you apply downward pressure with the "Z" handle, the tapping head will rotate in the same direction as the spindle is turning. When you raise the "Z" handle, the tapping head will rotate in the opposite direction even though the driving spindle continues to turn in the same direction. The floating action of the tapping spindle allows for slight mismatch of downward spindle feed with the "Z" axis handle and allows the tap to exit the hole properly when raising the "Z" handle. I have one of these units myself and use it when doing a large quantity of holes on the Bridgeport.

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              • #8
                Several Jarvic tapping heads on ebay for $50 or so.

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                • #9
                  This one is a single speed.

                  A friend has a reversing drum that he installed on his single phase, single speed mill, that's where I got the idea.

                  He always stops it before reversing.

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                  • #10
                    I have never seen tapping been done under power and the lathe mill is just used as a directional tool for guidance not power correct me if I am wrong Alistair
                    Please excuse my typing as I have a form of parkinsons disease

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                    • #11
                      I do almost all my tapping under power. Most of the time, I just chuck the tap in a drill chuck. I do a lot of "plug reversing" while going in and will run the tap back out under power until it is a 1/4" or so from coming out; at that point, I stop the spindle, release the chuck, raise the quill and unscrew the tap the rest of the way by hand.

                      For more than a fwe holes, I take the time to setup the tapping head: then its all done under power; all the way in and all the way out. I also have "tension/compression" drivers that use the Bilz tapping adapters: also "all power" tapping.

                      Once in a while, on very small threads, I use the spindle in neutral and turn the chuck by hand - not very often.

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                      • #12
                        Jim,
                        When backing the tap out under power, why do you stop short of bringing it out all the way? I do nearly all my tapping under power in the B'Port (VFD) except blind holes or very small taps. Even do small taps, if the first one, done by hand, seems easy. I always back the tap out all the way under power.

                        What am I missing?

                        <<Jim>>

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                        • #13
                          First off . Is it a lathe or a mill, single speed or 2 speed MOTOR. Does it have a brake to stop spindle. Answer these questions an I will tell you what you can or cant do. So can J.C. H.
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                          • #14
                            Jdunmyer,
                            when the tap is being backed out, it is giving my hand some feedback as I help raise the quill. When the tap approaches the last couple of threads and the tapered part is about to reach those last 2 rings, I'm concerned I may damage those by not having the quill retract at the proper rate.

                            Another way of saying it is that I'm not sure one or two threads, pushing against the tapered part of the tap will provide sufficient lift to continue pushing the quill or...

                            That as I'm helping to raise the quill, I may get slightly ahead, and "pull" the last thread or two.

                            On bigger threads, I don't worry that much about it, but down around #10 or maybe 1/4", it's a concern to me.

                            For the original poster, I am assuming that you have a "backgear" as I usually tap at less than 100 rpm when doing it this way.
                            Last edited by Jim Caudill; 11-14-2006, 03:11 PM.

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                            • #15
                              My Jet JMD-18 is a used milling/drilling machine.
                              A poor mans mill but I got it so I could have a better drill press with a milling table and the power tablefeed was a real bonus.

                              I found it too time consuming to drill so many holes at equal distances, on my old drill press.
                              Wit this, as you know, I can drill, crank, drill etc.

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