Motor for Watchmaker's Lathe

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Tortoise

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I have a watchmaker' 8mm lathe and wish to add a suitable motor drive. Many years ago I tried it using a 1/10 hp "sewing machine" motor with foot control and found it under-powered and hard to control the speed consistently. I want to mount the motor on a base with the lathe so the assembly remains portable. I've seen arrangements with 1/3 hp or even 1/4 hp motors that seem to be acceptable power. Although the lathe has stepped pulleys, I'd ideally like a more direct (electronic) method of speed control. Add to that I have very little knowledge of motors, and you'll understand why I'm asking for advice. Budget is ...."cheap as possible for something which will get quite intermittent use". Would one of the cheap 24v DC motors + speed control and power supply be a viable option, or not? Grateful for any advice.
 
Not a particularly difficult job to set up, but I would have thought a 1/3HP motor was a little over the top for the job myself...

And of course you will need a fairly hefty PSU- 0-24V at 15A- available but not particularly cheap (about $175-200 Au or about 100 pounds)

The motor itself would be fairly large- this is a typical 24v 1/3hp motor in size (be aware that many 'elcheapo' brands are quite 'enthusiastic' in their ratings- to put it mildly...)

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Specs
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A 7" x 9" motor to run a 8mm chuck seems a 'little' large I would have thought???

A 0-24v 15A variable PSU (commonly available in various brands)
Screenshot from 2023-10-03 08-41-57.png

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(this is from an Aussie supplier but I would think similar would be readily available in the UK)

A cheaper alternative might be 'thinking outside the box' and looking at electric bike motors- substantially cheaper, but you would need to step up in voltage though- most are 36 or 48v (again readily available), but you don't need a variable voltage one, as Ebike motors usually come with a speed controller (indeed while many have a 'twist' throttle', you can readily get 'foot throttles' as well but you might have to remove the chain drive cog that is usually fitted to put a belt pulley on (again, readily available)
Screenshot from 2023-10-03 09-05-08.png

This is one I have here that is going into a (old- VERY old lol) drillpress- its a 48v ebike motor that will run directly off my 48v battery bank (I'm offgrid running off solar) and cost considerably less than even the PSU alone above ($130 in total for the controller, pedal and motor, and an aluminium pulley to suit the belt drive on my drill) that motor is considerably cheaper, more powerful (almost excessively so in this case lol) than the one above... but again, it is a VERY powerful motor...
If you did use an ebike motor- then you would have the ultimate in portability- get a battery pack as well and run it 'anywhere' lol
;-)
(this is the drill press it is going to be in, currently in pieces, being rebuilt, that was when I first got it (it was literally being used as a garden ornament), but despite its appearance, is actually still in very good condition- years of sitting in a garden bed didn't do its appearance much good)
Screenshot from 2023-10-03 09-26-33.png
 

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Probably more power than you need but a drill with var speed has the whole package for not much money. Mount the pulley from the old motor in the drill chuck and you are just about there.
Regards
John
 
You can buy ready made kits to replace the rather gutless motors used on the Unimat SL lathes. These would probably be readily adaptable. Or you can buy the motor and speed controller separately and do it your self much more cheaply. Mine, very similar to the image, cost around £70 for the bits. Look on places like e bay. I bought the 200W motor and speed controller board as a package, then you just need a small project box to house the controller, a suitable pulley and some wiring. Should have enough power, the original Unimat motor is only 60W!
 

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I have an industrial sewing machine motor on my Pultra it is brilliant amazing torque even very slow although I have removed the pedal and changed to a potentiometer for speed control.
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Interesting - I think "industrial" must be the key as the domestic equivalent I had was poor in the extreme. Just searched, and yes, they are much more powerful than the domestic sewing motors.
 
I have a Cowells 90ME which is supplied with a 240v continuously rated 90w motor running at 1425 rpm. One of the most respected watchmakers lathes I believe and powerful enough for it's intended purpose though the gearing set up is a big part of that. You'll need to be able to reverse the rotation as well.
 

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I have a unimat and that was under-powered so I fixed up a 24v motor and little speed control I still kept the pulley format so I can get the lower speeds with high power more torque and a belt change to the higher spindle speeds it works really well.

24V motor.jpg

24V controller.jpg
 
I have a unimat and that was under-powered so I fixed up a 24v motor and little speed control I still kept the pulley format so I can get the lower speeds with high power more torque and a belt change to the higher spindle speeds it works really well.

View attachment 170174

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I made a new pulley for mine, the shaft on the new motor was quite a bit bigger than the original. I had to make the smallest step in the motor pulley 1.5mm bigger in diameter to allow sufficient room for the shaft without weakening the pulley. The other problem I hadn't thought of until I put it together is that the vented rear plate of the motor is aligned very nicely to collect any chips coming off the work ! You can see what I mean if you look at the image I posted earlier. I have simply fitted a thin aluminium shield to the motor body on the chuck side to prevent chips getting into the innards of the motor. The original motor is sealed, so you don't get this issue, but as a consequence they overheat quickly so you have to keep stopping to let it cool down. The new motor is much more powerful (200 vs the original 60W) and is ventilated so can be used continuously. Very pleased with it.
 
I made a new pulley for mine, the shaft on the new motor was quite a bit bigger than the original. I had to make the smallest step in the motor pulley 1.5mm bigger in diameter to allow sufficient room for the shaft without weakening the pulley. The other problem I hadn't thought of until I put it together is that the vented rear plate of the motor is aligned very nicely to collect any chips coming off the work ! You can see what I mean if you look at the image I posted earlier. I have simply fitted a thin aluminium shield to the motor body on the chuck side to prevent chips getting into the innards of the motor. The original motor is sealed, so you don't get this issue, but as a consequence they overheat quickly so you have to keep stopping to let it cool down. The new motor is much more powerful (200 vs the original 60W) and is ventilated so can be used continuously. Very pleased with it.
I did the same for the motor pulley the shaft was 8mm, I kept the old pulley with the old motor so could go back to original if needed.
 

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