Suggestions for Lathe motor setup?

Discussion in 'Horological Tools' started by berntd, Jan 31, 2011.

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  1. berntd

    berntd Registered User

    Jun 21, 2009
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    Hello all,

    I run a Lorch WW with what appears to be a 240V sewing machine motor and an electronic speed control, controllable with a potentiometer / knob.

    It is terrible in my opinion.

    On the slow speed, it will just sit there and buzz. If I turn it up just a little, it will suddenly zoot of way too fast etc. It is an unstable setup to say the least.

    These sewing motors appear way too fast for the lathe anyway?

    Someone suggested that I get a small 3 phase motor and a proper motorcontroller/inverter for the lathe.

    These can run from 0 to basically 3000rpm, reverse, accelerate/decelerate etc. Really cool. I have used them before for something else.

    It sounds great but is maybe overkill?
    The inverter is quite large, compared to the motor and lathe.

    What have other done?

    Kind regards
    Bernt
     
  2. StephanG

    StephanG Registered User

    Jun 24, 2007
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    I run the same setup as you describe and it works for me. Would not suite bigger work but Ok for watch work. You need to keep the drive pully on the motor as small as you can. Also those motors work bettor one way than the other. They are not designed to be reversable. Even though they will do it thay have a preferred way to run. Try running it the other way with the belt crossed over. If it works better you might consider mounting it differently to suit that direction of running.
    Otherwise there are a lot of DC motors now available. Check out what the electric bicycle people are playing with. You would have to find a suitable power supply but speed controlers are easy to get.
     
  3. gvasale

    gvasale Registered User
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    getting a three phase motor for that sounds kind of expensive. Guessing if you were in the US, new stuff would run over $300.00. A solution might be to run a jackshaft between the motor and the lathe. Not only would this give you more speed options, but might be a way to get past the all or nothing you seem to have now. On the other hand, you say this is a 240 volt motor? Is that standard where you are?
     
  4. berntd

    berntd Registered User

    Jun 21, 2009
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    Hello,

    Thanks Stephan!
    Maybe your speed controller is better? I have one from Jaycar. it is a black box module. It was on the lathe.

    My current motor (in fact all AC brushed motors) is not reversable unless you take it apart and swap the connections to the brushes. Is that what you mean?


    @all:
    240V is standard here for mains outlets here.

    A small 3 phase motor (125W) would cost around $75 but the inverter/controller would cost around $250!


    Kind regards
    Bernt
     
  5. movement2009

    movement2009 Registered User

    Apr 9, 2009
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    I also have problem for the motor when I get my first Lorch, the inverter/controller that I can find here is around US$400!!! Rather large, and expensive, and I actually don't know how it work!!! So I bought a Sherline motor, it works very well (220V here) except the noise (sorry for expect too much:D.)
    It seems someone can make the Sherline motor reversible but I just don't have the knowledge in electronic so I haven't try to modify it! The speed control of Sherline motor is good and for the reverse direction, I simply cross over the belt....or just reverse mount the lathe bed (with the headstock), I can work in both way....

    I found some photos for my Lorch set up, sorry for the motor is a bit out-of-focus....



    83009.jpg

    83010.jpg
     
  6. StephanG

    StephanG Registered User

    Jun 24, 2007
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    Hello Brent. I am just using a light dimmer I got from Lawrence and Hansen. According to the specs it will handle a load of 10 amp and that more than covers one of these motors.
    I got the idea from a friend who used the same moter and control to build a power feed for his Mill. Works fine but as I said does not give the same speed or power in both directions.
     
  7. berntd

    berntd Registered User

    Jun 21, 2009
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    Hello

    Movement2009, I have heard about the Sherline option and I believe it works well. My new mill is Sherline and I agree that the motor motor is rather noisy.

    Stephan, your setup will work about as well as mine but it all depends on the actual power, load and type of motor on how well it will work.
    My setup is identical to yours as this controller is basically a triac controlled light dimmer.

    With this type of triac controller, the motor torque is low at low rpm.
    If you have a light load, it will work fine but the green lathe belting on my lathe is rather rigid and provides quite a load on the motor.

    Are you able to switch on abnd start your lathe while the dimmer is set at a really low rpm?


    Kind regards
    Bernt
     
  8. cazboy

    cazboy Registered User

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    I have been emailing back & forth with a machinist in Oregon and he tells me that for small watchmaker's lathes, he uses motors from electric typewriters. He has one of his lathes currently set up for wheelcutting and has it powered with a motor from an old IBM Selectric.
     
  9. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    Another option is sewing machine motors. These
    usually have a foot peddle speed control that
    might be nice to have.
    Tinker Dwight
     
  10. StephanG

    StephanG Registered User

    Jun 24, 2007
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    Bernt,
    I have no problem running it at low speed. I use the biggest pully on the lathe and have the smallest I could make for the motor. Not much bigger than the shaft. For a drive belt I use a black O ring which has a very low drag. Just under 4mm section. I don't usually need much power as I use the machine for finer work ( I have a bigger lathe for larger items ) but have cleaned up a couple of bezel rings on it. I only tension the O ring enough to stop it slipping.
     
  11. berntd

    berntd Registered User

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    Hello

    @Tinker, my current setup is a sewing motor but without the footpedal. It sucks either way.

    @Stephan
    I also have a 6mm Lanco. It also runs from a sewing motor but with a foot pedal and the belt is an O-Ring.
    I agree with you 100% that the O-rings have much less resistance to the green lathe belting.
    In fact, they seem superior to the green stuff all round, also because one can stretch them over the differnt size pulleys.
    I don't need much power either as I try abd do watch work on the 8mm lathe.


    The foot pedal setup is weird because one overcomes the low toque non-starting problem by pressing it harder until the motor starts and zoots of into high rpm. Then one tends to let off until it slows down but for really slow speeds, one tends to press the pedal periodicly to try and keep the motor running and the result is sort of an average speed but no always predictable.

    Typewriter motor hey? Sounds great but wher on earth am I going to get a vintage typewriter motor these days? :D

    Kind regards
    Bernt
     
  12. rodstan

    rodstan Registered User

    Aug 16, 2007
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    Adelaide South Australia
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    hi Berndt,
    just my 2 cents worth,
    I use sewing machine motors on all 3 of my lathes and all have foot pedal speed control. I use rear transmission pulleys on all of them for speed reduction and green lathe belting. I never had any luck with a direct drive off the motor from way back in the day as it went too fast with no torque=glazed the metal and blunted hss gravers.Went back to using the original pulley system and have never had a problem. I use it for overhead transmission for milling and damascening and wheelcutting /topping.If the wheel blanks are thick they tend to stall the cutter. The pulley reduction provided enough controllable power for staff turning and pivot drilling.
    My mill is a sigma/bca 10 mm jig borer running a 1 hp motor with green lathe belting--never failed--it also uses idler pulleys and stepped drive.
    Might I suggest getting a rear pulley drive system.
    I have used dc motors and control boxes on other machines here but they tend to "hunt" at low speeds and if there is no resistance for the cutter they stall--rather tedious:)
    The only machine I have fitted with a dc motor is a 6 mm micro drill press about 4 inches high and drilling sub millimetre---high speed with virtually no torque. It is a purpose built machine for very thin material.
    For us Aussies the best compromise is the sewing machine motor, there are probably better motors about, depending on what you need, but at $25 for most sewing machine motors you cant go wrong for basic machining.Mine have lasted for 20+ years and still going strong:)
    catch u later
    Regards
    Rod
     
  13. berntd

    berntd Registered User

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    Hi Rod,

    Sounds like you have a really good tool setup. I envy it :D

    May I ask what rear tranmission pulleys are ?

    If there is hope for the sewing motor system, then I will stick with it and see if I can fix/improve it.

    I currently have the motor mounted behind the lathe and then the belt goes from the motor pulley to the lathe pulley.

    Kind regards
    Bernt
     
  14. StephanG

    StephanG Registered User

    Jun 24, 2007
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    This ebay add is for something else but the picture will explain a rear transmission perfectly.

    120679958653
     
  15. berntd

    berntd Registered User

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    Oh,

    That would be the whole sort of coutershaft thing then?

    I really thought that was way outdated and nopbody used it any more but now I see what you mean. It woudd allow for a much beter speed reduction between the motor and the lathe.

    I did notice that some of the countershaft setups sell for heaps of money on
    ebay.

    Funny about that...

    I need to see itf that would be cheaper than a small 3 phase motor with a proper VS drive.

    Regards
    Bernt
     
  16. rodstan

    rodstan Registered User

    Aug 16, 2007
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    Watchmaker, clockmaker of 35 years,hand engraver
    Adelaide South Australia
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    Berndt,
    Stephans picture shows one of the varieties, there are others.If you get one you dont need to change motors, you could probably improvise with a 3 step pulley or 2.
    It made the world of difference for me.
    Attached a picture of my lathe bench (under the mess) that was b4 xmas,My camera is flat so it needs a charge--anyway you might pick up the 2 back pulleys 83217.jpg on the lathes each side of the micro drill press.
    Regards
    Rod
     
  17. praezis

    praezis Registered User

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    Berndt,
    the described problem is typical if you use the wrong electronic speed control. You need one with torque compensation.
    My motor (sewing type) cannot be stopped by hand at low and very low speed. A controller can be made yourself for <10$, it has very few parts. I can post a schematic if there is any interest.

    Regards,
    Frank
     
  18. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    Newer sewing machines use better controllers than
    the older ones.
    The best setup is a full servo system but that gets
    really expensive.
    Most simple system now days use a clever method
    of regulating the speed. When a DC motor is running,
    there are two components to the voltage drop across
    the motor. One is the IR drop of the windings and brushes.
    The other is back EMF.
    The back EMF is directly proportional to the motors speed,
    with a constant field type motor.
    By measuring the current and voltage across the armature,
    one can determine the speed of the motor under various
    loads and correct to maintain a constant speed.
    This works well for motors with permanent magnets or
    a fixed voltage field winding ( shunt wound ) but doesn't
    work well with series field coils.
    I would guess that most new sewing machines use this
    type.
    One does have to tune the circuit to the motor as the
    feedback system needs to have a matching resistance
    as a reference of the motor.
    Tinker Dwight
     
  19. rodstan

    rodstan Registered User

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    Watchmaker, clockmaker of 35 years,hand engraver
    Adelaide South Australia
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    attached better pictures of my pulley systems.I prefer low tech solutions, its hard to find anyone about down here that wants to supply dc motors or speed controllers.
    I keep the old treadle tucked away just in case:)
    Anyway best of luck whichever way you go
    Regards
    Rod
    (the bench really is clean, photo enhancement made things look rusty,didnt help) 83295.jpg 83296.jpg 83297.jpg
     
  20. Jerry Kieffer

    Jerry Kieffer Registered User
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    #20 Jerry Kieffer, Feb 4, 2011
    Last edited: Feb 4, 2011
    Hey Berntd

    Is this the same Lathe you were trying to machine a staff on, but had Runout, Cross slide, lathe tool and now motor Issues :???: If so, you are a very patient person. If I needed to get something done under these conditions, anger management would be required probably after the five pound hammer exercise.

    Maybe I can make a suggestion for a break while you are resolving these problems.
    If you would like to experience machining a staff without Drama, it can be done on the Sherline Mill you said you just purchased.
    You would first set up the Mill as a Lathe per the first attached poor quality photo. I do not have time to set up lighting and shoot a clear photo today. But I think you can get the general idea. In this arrangement, all axis are fully adjustable for easy alignment setup. Remove any headstock spacer blocks to make the setup more rigid. The "Z" axis should be lightly locked when making fine adjustments and the X and Y axis locking screws should be set for light resistance during operation. A vise mounted tool post is easily machined with the mill. The one shown is the Sherline lathe spacer block version that is really not long enough for this setup when mounted in a vise.
    The second Photo shows a couple of quick cuts with a chipped brazed carbide tool that happen to be handy.

    This setup is of course not as rigid or efficient as the lathe, but suprising useful and highly accurate in a pinch. Especially for small parts like a staff. If I have time, I sometimes demo cutting a staff with this setup in the NAWCC school workshop WS-120 to show versitility and capability of the Mill. It is primarily done to get the student to think about setups that will resolve machining problems.

    Again for anyone reading this, I am not suggesting this setup to replace a Lathe, but as a setup for Berntd to experience machining a staff without Drama (With what he has) and as a setup exercise.

    Jerry Kieffer 83331.jpg 83332.jpg
     
  21. bbwatch

    bbwatch Registered User
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    Frank - I could use a schematic. I've had to live with the runaway problem with footpedals and have tried the router speed controllers. Please send me the schematic at bbwatch@verizon.net.

    Thanks,

    BarryB
     
  22. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    Kind of reminds me of pictures of old machine shops.
    A shaft running overhead with leather belts dangling to
    the various machines.
    Tinker Dwight
     
  23. Dave B

    Dave B Banned

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    My countershaft is the same as rodstan's, except it has a few more pulleys on it. I think it might even be the same brand,, as all the turnings and the lever look the same as his. I got it a couple of years ago for $50.00 on eBay. I just kept bidding on them with a max bid of $50.00, until I won one.

    The motor is a Singer sewing machine motor, and I am powering it through a router speed controller which I picked up from Harbor Freight for the grand sum of $22.00 plus tax. I have been using this setup for several years now, and am happy with it. I have found that even at low speeds, the belts slip before the motor stalls. But The largest diameter I have ever tried to cut on the lathe was only 3/4 inch, and was "free machining" brass. I suspect cutting that diameter steel, or something really stringy, like bakelite or pvc would be a whole different story. 75824.jpg
     
  24. praezis

    praezis Registered User

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    Here comes the schematic. Components are calculated for 230V mains voltage (or lower). The pot is rated 1W but 0.25W should also be fine (plastic arbor and knob!).
    I use this with a 100W motor. This electronics is only intended for brushed universal motors like sewing machine type or power drills.

    For those who do not like soldering I can supply a ready assembled board (PM then).

    Regards
    Frank 83346.gif
     
  25. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    This is a typical PWM control as found on a hand drill or such.
    It works well at higher RPMs and under light loads but not
    so good at slow high loads.
    It would surely work better than the old carbon pile type
    sewing machine control.
    Tinker Dwight
     
  26. praezis

    praezis Registered User

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    Hi,
    you can adjust from zero, and as I mentioned, you cannot stop the motor with your hand at 100-200rpm! High enough load for me :)
    Regards,
    Frank
     
  27. movement2009

    movement2009 Registered User

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    #27 movement2009, Feb 4, 2011
    Last edited: Feb 4, 2011
    So happy to see a lot of set up......:)

    Dear Rod,
    Good Morning. The two pulley of your set up is in my want list for a few years, they are not cheap on ebay, most of them over US$200!!! Still hunting......
    May I ask what is the lathe set up of the 2nd photo for? You make the middle part (the brass disk:???: between the headstock and the milling attachment) by yourself? For damaskeening (don't know how and want to know if a lathe set up can make such task) or something else?
    I would also like to know what is the machine in photo 3, is this your milling machine or a drill press? Much appreciated if you can tell us more.....I apologize if it is a bit off topic!

    Regards,
    KK Au
     
  28. rodstan

    rodstan Registered User

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    hi,
    the second picture is a Boley Leinen 8mm, the brass disc is a factory dividing head mounted on a vertical slide which in turn is mounted on the compound slide. I use it for wheel cutting and other uses for divisions when milling with the head stock,. It is part of a very large Boley lathe set up. The Lorch --first picture also has a 7 inch headstock mounted dividing head and multiple compound slide with vertical milling head
    The last picture is a BCA Sigma rotary jig borer, which finds uses in machining parts. It has about 20 10 mm collets with it so it can be used with dental burrs up to full size milling and fly cutters. It also holds very small drills for accurate plate drilling. It weighs about 100 kilos :)
    The damasceening head(not shown) mounts on the compound and looks similar to a pivot polisher but has a mutitude of cup wheels in steel, ivory and brass and varying diameters and thicknesses, all driven by an overhead drive, operating against a counter rotating headstock.Its good for refinishing winding wheels etc.
    Regards
    Rod
     
  29. berntd

    berntd Registered User

    Jun 21, 2009
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    Hi Tinker,
    This is not a PWM (pulse width modulator) control at all. It is not a phase shift dimmer either.
    It is a rather clever half wave feedback circuit. I have never seen it used anywhere before but now remember it from my student days.

    Kind regards
    Bernt
     
  30. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    I see now, the back EMF would hold of firing
    the SCR. It is like a modified PWM. One should
    be able to put a full wave bridge in front of
    it to get the full speed of a AC motor.
    It just needs to be non-filtered.
    Tinker Dwight
     
  31. berntd

    berntd Registered User

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    Hmm.. At a glance, you could be right. It may work but it will doublein effect double the frequenct. Someone should try it. :D

    I want to build one up but haven't got a suitable pot. I am looking into it.
    I am pretty sure it will be a vast imnprovement on the one I have now.

    Thank you Frank!

    Kind regards
    Bernt
     
  32. praezis

    praezis Registered User

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    very true!
    I did, it does not work with bridge rectifier, I assume by the inductive phase shift between voltage and current.

    Regards,
    Frank
     
  33. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi Frank
    You're most likely right. You might need the entire
    half cycle to turn off the SCR. I'd be interesting to
    put a scope on things and find out what is actually
    happening.
    Another thought occurred to me and that would
    be to duplicate the SCR circuit for the other half
    bridge. The would still cause the SCR with no
    current to turn off since the other SCR would
    supply the needed current and back bias the
    SCR that had just fired. You'd need a double
    ganged pot as that part would need to be replicated.
    Tinker Dwight
     
  34. berntd

    berntd Registered User

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    Hi Frank, I sent you another PM.

    Regards
    Bernt
     
  35. auto249243

    auto249243 New Member

    Sep 19, 2010
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    Suggestion 1: Sherline lathes motor/speed controller setup, I think that they will sell you one as a separate part.(more expensive solution). You will likely need to turn a custom pulley for yourself. They seem to have very good reviews and you will have plenty of power and control.

    Suggestion 2: Look at what people that have Taig lathes are doing for motor and speed control.

    Notes: router speed controls work just fine on universal motors, but they will also work on DC PM motors if you place a bridge rectifier between the controller and the motor. They work best( most torque & power) at 50-100% speed. If you need lower speed select a lower speed motor, step pulleys, and/or a jack shaft setup.

    If you really want to mess around with the electronics, read some of the Triac application notes that Teccor has on line.

    Of course, appropriate electrical safety knowledge and precautions apply.
     
  36. wefalck

    wefalck Registered User

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    I have been using the Sherline power-pack (motor and controller) for almost ten years now on my lathes as well as the Wolf, Jahn & Co. milling machine. All are controlled by a on-off foot switch.

    The motor is housed in a wooden box at the back of the bench that also provides a stable mount. The controller is screwed-down on top of it:

    View attachment 4684

    This is an earlier version for the Wolf, Jahn & Co. 6 mm lathe:

    View attachment 4685

    In the meantime I have two removable boards on which respectively the D-bed and WW bed are screwed down on. These boards in turn screw down onto the lathe workbench and thus can be interchanged (I don't have enough space to keep both set-up)

    And finally the set-up for the miller:

    View attachment 4686

    The controller is screwed onto the box housing the motor on the right.

    I found that the Sherline DC motors give a lot more torque than AC sewing machine motors. Perhaps no wonder, as the input rating is 300 W as opposed to 90 W. However, the so-called repulsion motors (e.g. Multifix brand in Germany) seem to run quieter and are also reversible. The Sherline motor could be made reversing (for screw-cutting) with a simple switch and a bit of re-wiring, but Sherline advice against this, as the brushed are better run-in, when using it in only one direction (pers. comm. and also on their Web-site, I believe).

    wefalck
    www.maritima-et-mechanika.org
     

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