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Thread: New powerfeed for lathe - DC variable speed

  1. #1
    Join Date
    Jan 2017
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    103

    Default New powerfeed for lathe - DC variable speed

    My import 12x36 is an older belt drive with the open gears on the far left end and open style quick change gearbox. When using the power feed at anything above threading speeds it makes a lot of noise and a lot of the moving pieces are just on bronze bushings. I'd seen one other person with a very similar lathe adapt a DC motor to the feed rod so I decided to do the same. The results are blissfully quiet power feed and a lot of wear and tear saved on the gear end. Also on the fly feed rate changes. The only downside now is I have no idea what my feed rates actually are, but in the little bit I used it today getting it up and running I'm not missing that.

    The motor is a power seat motor available on amazon for $17 and the speed control is a 15A model also from amazon. I installed a DPDT switch to give me fwd/rev/stop. The chain and sprockets are #25 from surplus center, tiny little things. Running it for now on a extra car battery I had kicking around as I heard these controllers don't necessarily like switching power supplies. The top speed is about perfect and I'm getting wonderful surface finishes when dialed down. I'm going to use the same motor/control for a power feed for my mill, but I'll be running off 18V LiIon cordless tool batteries for more speed.


    Last edited by JCByrd24; 04-24-2018 at 05:31 PM.

  2. #2
    Join Date
    Jul 2016
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    Brampton, Ontario
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    I run anything and everything off switching supplies, I've never had an issue and don't recall hearing anyone else having issues either.

    I really like the idea of tossing the change gears for a motor. If a stepper was used, its halfway to a pseudo-CNC

    Sent from my SM-G930W8 using Tapatalk

  3. #3
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    Nice job. I suppose you'd eventually want to enclose the chain pretty well.

    Once you get your power supply setup you could carefully measure how long it takes to feed a longer distance and then calibrate the knob. You might also find that a replacing the pot with one tuned specific to your application would allow you to use the full range on the knob and accurately choose a feed.

    Or maybe you'll just calibrate via voltage? Once you have the volts vs feed factor figured out, a scaled display would display feed directly. Does it slow down much under load?

  4. #4
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    As that is not a motor that can be CNC'd easily, and you DO have the QCB, I am not sure what the real advantage is. Noise, OK, but not being able to know the feed would be a non-starter for me.

    it seems you should be able to know, at least roughly. I assume the readout gives voltage. If so, you should be able to time a certain distance, and get speeds for various voltages. Then, a table of voltage vs spindle speed could be made that would give a decent indication of feed per turn. A bit of fun with MS Excel.

    The load applied would probably affect the speed a bit, but snce that is a gearmotor, and the feed loads are not usually heavy in finishing cuts, I would think you could do pretty well in terms of accuracy.

    I see that two of us had the same idea and were typing at about the same time.
    1601

    Keep eye on ball.
    Hashim Khan

  5. #5
    Join Date
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    Woodinville, WA
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    Nice work. Consider having the on/off switch on your carriage. If you are working close to the chuck it's a way to reach for the feed switch especially if you have a small landing zone.

  6. #6
    Join Date
    Oct 2006
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    Ivins, Ut
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    Nice, clean install. Don't worry about not knowing the feed rate. I never look at the numbers, I just know from experience where to position the QCB levers to get what I want, and after a few hours playing with your setup, you'll know where to set the knob. I personally don't think totally enclosing the chain is important, but I would do a half-cover that would deflect debris from the top and inside.

  7. #7
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    Yep... I also have no idea or really care about actual "number". I have levers for 32 (?) feed combinations. I use maybe 4 of them. Of course, mine are "in/rev" and this is now independent of spindle, but you will quickly figure what you need for your usual tooling/speeds. As for "cover", how much debris is going to get on it at the tail stock end anyhow?

    I use that same PWM controller for high power LED dimmers.
    Last edited by lakeside53; 04-15-2018 at 11:54 AM.

  8. #8
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    If you fitted a switch on the left hand end of the apron, with an adjustable collar on the feed rod, you could set it to stop at a predetermined point.

  9. #9
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    Quote Originally Posted by Robin R View Post
    If you fitted a switch on the left hand end of the apron, with an adjustable collar on the feed rod, you could set it to stop at a predetermined point.

    Dang, I like that!

  10. #10
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    Also .. on my lathe if you find that your not happy with the speed you have selected, you
    have to stop the lathe to change it. With your's, you can fine tune it on the fly, sounds
    like an advantage to me.
    John Titor, when are you.

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