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speed regulator

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  • speed regulator

    I have a regular bench top drill press, I realy like to use, but I find the belt spindle speed at it's lowest is still to fast for the drilling I do, (on my mill drill I can drill very acurately at speeds as low as guessing 20 rpm's, but with plenty of torque, and it drills superb through steel and aluminum stock, it is a DC motor)
    however my drill press has longer Z axis travel, and would like to utilize my drill press for drilling. Of course the motor is your normal 1 PH. 120V. ac.
    I tried the router controle from HF. works good for a router, but can't vary the speed so well with this drill press, also when it runs slow, it loses all torque, so router controlers are out of the question, what's the next best, speed controler that would give me very good regulation at slow speeds and plenty of torque, within a $100 range, were talking about a hobby drill press.
    with that kind of price range probably not anything worth while, but I'll still ask any how.

  • #2
    I'd suggest a double step sheave pulley arrangement. I had a craftsman lathe that was way too fast, I did the double reduction step sheave (invert one) and put a mandrel end on one end of the second one.. I used it for polishing.. (it was horizontal) That will get your motor more inside it's torque range and not break the bank.

    David Cofer, Of:
    Tunnel Hill, North Georgia


    • #3
      Thanks David,
      but my drill press already has the step pulleys arrangement for 5 speeds the lowest speed is 620 rpm's.
      That's why I thought about elctronic speed control or something.
      However as I'm thinking more about this, maybe I could buy a DC motor from "little machine shop" the one used on my mini lathe, and buy a speed controler to go along with it, and convert the whole thing to a DC setup.
      and it won't be to expensive, maybe less than $200 altogether, but I would really be able to utilize my drill press to the fullest potential of the drilling I do.

      Thanks again I appreciate your help.


      • #4
        I was thinking along the same lines as Ibew.
        Add a jackshaft with a bearing on it, mounted to the side of the drill press frame. Add a step pulley to it, and drive it with the motor, then back to the one the motor was driving originally. Probably cut the speeds drastically, and increase torque.
        David from jax

        Have gun, will travel.
        A serious accident is one that money can't fix.


        • #5
          My lathe already had step pulleys. I added two on a arbor shaft.. Effectivly doubling the reduction ratio.

          I sold "3" 3/4 hp dc motors on ebay. I think any motor only has resolution to run erratic at slow speed. Mechanical correction to get the motor back on it's power curve helps.

          I got, $178 for one, $150 for another, and $108 for the third.

          Look on ebay for more.. Not mine.. but they are on there from time to time.

          David Cofer, Of:
          Tunnel Hill, North Georgia


          • #6
            Ok, now I understand what you guys meant by adding another pulley or set of step pulleys to further reduce the speed, I'm seriously looking into this at every angle possible.

            Thanks again for all your helpful replies.


            • #7
              add another motor to your drill press table.
              what counts here is relative speed between your drill chuck and your workpiece (think about the times your tapered shank drills come loose in the lathe's tailstock.. everything is spinning real fast, but no cutting is taking place).

              if you can get your drill press's vise to spin at 1440rpm, while your chuck is spinning at 1445, you're effectively working at 5rpm.

              not only will this boost the fear factor, but you'll also lose all of your torque.

              thinking out of the box,


              • #8
                What you been smoking?
                Free software for calculating bolt circles and similar: Click Here


                • #9
                  yeh, I suppose that's another angle to look at, not a bad idea, but instead of using another motor maybe I could gear the chuck spindle to the rotating vice with a reduction of 30:1 that would be positive drive so one motor can perform both spinning operations, that should take care of this dilemna.


                  • #10
                    how do you get those strupid pictures thumbs up and smileys and stuff inside the paragraphs. mine endedd up outside the post or whatever ya call it..

                    [This message has been edited by dvk (edited 09-20-2004).]


                    • #11
                      The reason your DC motor doesn't lose torques is the drive controller which most likely varies the DC pulse width.(PWM)
                      The electronics to vary the FREQUENCY of an AC motor is quite expensive and complex.
                      The brushless DC motors are the best in my opinion but can be costly. The Sherlines use the brushless technology and anyone who has one will tell you they are quite good although at 20 rpms there is only one revolution in 3 seconds so even the brushless we exhibit 'cogging'.
                      The problem with 'V' belts is efficiency losses if you can run a cogged belt like on most car cam shafts you'll have better efficiency and it will run quite.


                      • #12
                        I used 20 rpms as a guess,in all reality definately not what I realy can use anyhow, no my micro mill has that speed regulator and at the lowest usable speed is probably 60 rpms, I can count each flute as it they go by on a 4 flute end mill, and yet surprisingly has enough torque that I can't stop it holding the spindle, that elimninates all the chatter when step drilling from one size bit to another, plus I can vary the speed as needed once the bit is well seated. Thyat's why I think a dc motor and controler from mini lathe would fill the bill reeal well for this aplication.
                        But this is a project in my list, got other projects ahead.
                        Thanks everyone for your input.


                        • #13
                          What I'd like to get across.

                          Every motor can not maintail horsepower at slow speed. What comes to mind is my inverter drive, at slow speeds the horsepower is severly crippled. The motor is designed to apply torque at at specific RPM w/rotating weight adding to the output and stabilizing speed. A ac squirrel cage motor has a "slip" percentage where the fields outrun the armature. At slower speeds this is MUCH higher. When you apply a load it slips real bad sometimes running erratic.

                          A Dc motor has a much better turndown ratio. It will apply torque while sitting still. But will still be erratic over a percentage of lower speed. The Square wave drives pulse a much higher current at a lower duty cycle. BUT, you are still limited to the Amperage the motor is rated for.

                          No matter what any salesman says the speed regulation is still a percentage. Ie 1850=100% and 925 = 50%. Usually it is 50 percent stable.
                          The "Open loop" or "blind drive" does not have a encoder feedback to correct speed and outputs/regulates a current according to speedpot input. It keeps a constant current instead of a constant speed.

                          I thought my 2hp Ac inverter converted cnc would not need the "low" head ratio because of the turn down speed.. I was wrong, I had to add in the controls.

                          I'll keep my eyes open for some more DC motors, Unknown when.. the 4 I had before came in a room of parts I bought for $40. THe things I bought the room for, well I could not even sell them. Such is Life..

                          David Cofer, Of:
                          Tunnel Hill, North Georgia


                          • #14
                            David I agree 100% what your saying,
                            in fact I just came on line, to try to right the wrong I was giving the impression of about low speed high torque motor, my micro mill gives extreme low speed with extreme high torque, I think only becaise it is gear driven, the motor itself is not going the low speed I was giving, it's the spindle that's moving slow with high torque.
                            If it wasn't for the gear head I would not be getting this kind of results.
                            I would have to gear drive my drill press to get the same reesults probably.
                            thanks again guys for your help.


                            • #15
                              David is right......first try to buy or build an intemediate pulley assembly between the motor pulley and the spindle pulley. Delta had them on their 15" Drill Presses as an option, as did others. You should be able to get 2-300 spindle RPM from an 1800 rpm motor.

                              If you want to go lower, then add a DC motor ( as they have said, the torque remains constant but the horsepower drops off as you lower the speed ). Using the intermediate pulley, you should be able to get down below 100 RPM at the spindle.