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Drill press project - single phase motor (re)wiring

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  • Drill press project - single phase motor (re)wiring

    I picked up an old drill press off Craigs. Drill only ran in reverse, so i got it cheap with hopes that I can set it straight.

    The original motor was been replaced and wiring completely botched in the process, hense reverse-only operation.

    Motor is a 1/4hp KC type General Electric, single phase, capacitor start motor - very old. Currently it's missing a relay and the drum switch. Switch has been replaced by a basic SPST/SPDT light switch.

    This would all be OK, except the drill only spins in reverse which is pretty much useless (unless you only use it as a drum sander.)

    Plan at the moment is to rewire it back to original forward/backward operation. This means replacing the missing relay and switch. I will be following the info posted on another board:

    http://www.practicalmachinist.com/vb...tml#post579470


    - Relay will be 120V rated for 1/3hp or 240V/10A (motor is spec'd at 4.8A 1/4hp)

    - Original drum switch is unavailable, instead I plan to use a heavy duty DPDT Carling switch to select direction and a second SPDT Carling to switch AC input.

    Will let you know how I get on. Meanwhile feel free to comment. My knowledge of single phase motors is 2 days in the making, so fill me in.

    Oh and here are some visuals: http://picasaweb.google.com/ybiteykin/DrillPress#

  • #2
    Nice looking drill press! Good luck with it! I could never understand how people can abuse the tables like that.

    I will be watching about the fwd/rev wiring. My 110v lathe has a drum switch which was wired by a blind kid when I got it. I'm not a complete idiot but I am no pro either when it comes to wiring. So I wired up the drum switch the way I figured it should work (reversing the neutral and hot wire for rev). I found out that doesn't work. lol The motor runs forward in both drum positions.
    Andy

    Comment


    • #3
      1. The DPDT switch for reversing, do not use a
      "center off" unit. This will shut off the starting winding,
      someone else may try to start it in the middle, and burn out
      the winding.

      2. Re-alize you will not have instant reverse, unlike a
      3-phase motor, you'll have to stop the motor, let
      it coast to a stop, and then re-start the other direction.

      3. Get a foot pedal switch, and wire in series with the
      main start/stop switch. That way, when changing bit's
      or such things, the main switch negates the function
      of the foot pedal switch.

      Comment


      • #4
        i'm encouraged by the feedback so far. will see if my abilities can keep up..later today.

        yeah i thought at first reversing the leads would do the trick, but after thinking about it (and as you found out) .. that doesnt work. it's AC so it's already changing polarity 60 times / second.

        the direction of spin is controlled by the starter coil and capacitor. that starter circuit gives it an initial boost and then disengages letting the primary coil do the work. the position of this capacitor within the starter circuit dictates a CW vs CCW starter boost.

        it gets more silly from here.. dynamic braking, instant reverse, things I cant understand yet, etc.

        - "no instand-reverse" yep i realize this, np, it'll be spinning in forward 99.9% of the time

        - "DPDT" ditto, i had a choice of center-off or on/on, picked the on/on as advised.

        - dig the footswitch idea. i just built one for my guitar amp, some leftover parts ... just need a momentary footswitch.
        Last edited by sgtpepper; 02-04-2010, 06:13 PM.

        Comment


        • #5
          Originally posted by vpt
          I will be watching about the fwd/rev wiring. My 110v lathe has a drum switch which was wired by a blind kid when I got it. I'm not a complete idiot but I am no pro either when it comes to wiring. So I wired up the drum switch the way I figured it should work (reversing the neutral and hot wire for rev). I found out that doesn't work. lol The motor runs forward in both drum positions.
          To reverse a typical capacitor start single phase induction motor, you have to reverse one winding (typically the start winding), not both. It is the phase of the two windings relative to one another that matters.* For a capacitor run motor, you switch which winding is fed through the capacitor.

          Comment


          • #6
            I am not sure why you want the relay, unless you have the same type start switch as in that motor shown by Paula in the other thread. Or unless you want drop-out on power loss.

            The relay otherwise is NOT needed for reversing. The particular system shown is for "instant reverse", essentially by "starting the motor in reverse" when it is already going "forward". It is VERY stressful, and may be productive of loud and unpleasant noises. It requires that specific type of start switch, AND the particular type relay. You do not need it, and it is not even that helpful.

            The common ordinary motor is reversible by removing power, reversing the start winding, and re-starting after letting it come to a stop. That should be good enough for most anyone.

            It can be done with two switches, which I did on my lathe years ago. it can be done with a regular single-phase OR three-phase drum switch, which I upgraded to later. (I now use the drum switch with 3 phase power).

            The picture is a diagram of a single phase reversing setup using a standard 3 phase drum switch. it is for a 230V motor, but the principle is exactly the same for a 120V, if you ignore the extra winding and pretend it is just a piece of wire.

            The switch does not break both sides of the line, but that is common , even in Europe. Since the plug is your safety disconnect, there is no safety issue whatsoever.



            BTW, I have a drill press of that type out in the garage......... without the table holes....... Its quality is.... well it makes holes, generally nearly where they are intended......
            Last edited by J Tiers; 02-05-2010, 12:06 AM.
            1601

            Keep eye on ball.
            Hashim Khan

            Comment


            • #7
              Originally posted by sgtpepper

              The original motor was been replaced and wiring completely botched in the process, hense reverse-only operation.

              Motor is a 1/4hp KC type General Electric, single phase, capacitor start motor - very old. Currently it's missing a relay and the drum switch. Switch has been replaced by a basic SPST/SPDT light switch.
              I have a Taiwanese ringer for that press, 12 speed. think the motor is at least 1/2 if not 3/4. is NOT reversible. no relay either . . .

              I know my motor probably isn't the best, but wonder if 1/4 will be big enough for you

              There is a light socket in bottom. There used to be a real cheap double switch (one of the old ones where you hooked different devices together on one yoke) one for the motor, and one for the light. I replaced with a hp rated toggle and a push on / push off switch for the light (avoids confusion) on a blank utility plate, I had to fudge the hole spacing as it wasn't the same as a box
              Last edited by fredf; 02-05-2010, 12:34 AM.

              Comment


              • #8
                yeah, teh last post reminded me that you mentioned 'original fwd/rev action", which mine certainly never had....... FWD only.

                yes, light switch plus motor switch. The light is pretty handy, so I'd suggest it if the socket is still there.

                otherwise, don't mess with FWD/REV.... just get it going forward. I misread you to say that you wanted reversing for some specific reason.
                1601

                Keep eye on ball.
                Hashim Khan

                Comment


                • #9
                  sgtpepper, why do you want to run a drill press in reverse?
                  It's only ink and paper

                  Comment


                  • #10
                    Originally posted by Carld
                    sgtpepper, why do you want to run a drill press in reverse?

                    It's great for tapping. Label the reversing switch "in-out".

                    "Since the plug is your safety disconnect, there is no safety issue whatsoever. "

                    Reaching over to remove the plug every time your hands come near the chuck
                    (like using the key to tighten up or change a drill bit) is a pain.
                    Flipping the on/off switch (the original one before modification) is easier,
                    and will be used more often.
                    Last edited by digger_doug; 02-05-2010, 08:19 AM.

                    Comment


                    • #11
                      Originally posted by Carld
                      sgtpepper, why do you want to run a drill press in reverse?
                      I always used to run the drill press at school in reverse.

                      The left hand drill bit set at the back of the cupboard was actually sharp, whilst the ordinary set was usually in a very poor state.


                      Of course, that might have had something to do with the fact that some people wouldn't notice if I left the press in reverse and just try and plough their way through.
                      Paul Compton
                      www.morini-mania.co.uk
                      http://www.youtube.com/user/EVguru

                      Comment


                      • #12
                        Originally posted by J Tiers
                        I am not sure why you want the relay, unless you have the same type start switch as in that motor shown by Paula in the other thread. Or unless you want drop-out on power loss.
                        I dont see the point of the relay in my situation either. In fact I can't even verify if it had a relay from the factory.
                        Paula's motor looks ALMOST identical, but no way for me to know if mine in fact had the same relay. Although something is definitely missing from the place where the relay would have been. Some home-brew cap came in it's place.

                        OK ditching the relay, for now.. although .. i do like the dropout on power loss feature. hm..


                        Originally posted by J Tiers
                        BTW, I have a drill press of that type out in the garage......... without the table holes....... Its quality is.... well it makes holes, generally nearly where they are intended......
                        I kind of like the holes... looks like the surface of the moon.
                        as far as precision, not too worried. no high expectations since i paid 50 bux for it.


                        Originally posted by fredf
                        There is a light socket in bottom.
                        Yeah, I just realized that this morning when i went down to take some pictures.
                        Will definitely be retro-ing a light in there..somehow.



                        Originally posted by Carld
                        sgtpepper, why do you want to run a drill press in reverse?
                        ..in case I decide to move to Australia.. ?

                        Comment


                        • #13
                          Originally posted by digger_doug

                          Reaching over to remove the plug every time your hands come near the chuck
                          (like using the key to tighten up or change a drill bit) is a pain.
                          Flipping the on/off switch (the original one before modification) is easier,
                          and will be used more often.
                          SAY WHAT?

                          What on earth would suggest you should do THAT? "whenever your hands come near the chuck"...????? Eh?

                          Are you under the impression that I suggest no power switch? Because if so I might suggest you re-read the post.

                          The original switch on most of those DPS that I have seen, in common with virtually all such switches, breaks ONE side of the line..... This is what the 3 phase drum switch does when wired single phase.

                          When the electrical circuit is open, EITHER WAY, the motor isn't turning, there is no power. I can certainly appreciate safety, but that is "out there".

                          My comment on the safety disconnect was from the standpoint of ensuring the electricity is disconnected when working on the wiring....... In place of a disconnect switch on the wall which would be used for machines wired a permanent connection and no plug.

                          And since the original switch does the same thing as the drum switch, I guess you will have to pull the plug anyway..... if you want to be extra super-duper safe. Now I have so far never found the switch to become mysteriously turned on when I was in a different part of the shop, but maybe you do.

                          Are you sure you shouldn't shut off the main breaker when you replace a bulb or plug in a lamp..........................?

                          Don't go to a regular machine shop, many of the machines keep the motor on at all times, and disconnect the spindle with a mere mechanical clutch......... "incredibly unsafe", I suppose you would say.
                          Last edited by J Tiers; 02-05-2010, 09:54 AM.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Originally posted by J Tiers
                            otherwise, don't mess with FWD/REV.... just get it going forward. I misread you to say that you wanted reversing for some specific reason.
                            yeah, no immediate need for reverse. so maybe i'll keep it simple for now and wire it FWD only plus a light. Light would be key.
                            maybe add a DPDT for REV operation later if a situation calls for it.

                            thanks all for the input. hopefully will have some progress to report later tonight. didnt get my hands on it yesterday.

                            Comment


                            • #15
                              Originally posted by J Tiers
                              SAY WHAT?

                              What on earth would suggest you should do THAT?
                              Because you wrote this:

                              "The switch does not break both sides of the line, but that is common , even in Europe. Since the plug is your safety disconnect, there is no safety issue whatsoever. "

                              I took this as you saying that the on/off switch was an unecessary expense
                              if using a foot switch.

                              Comment

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