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Lathe motor

Help would be appreciated.

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3-Phase Conversion and Other Alternative Methods of Powering a Mini-Lathe

3-Phase Conversion and Other Alternative Methods of Powering a Mini-Lathe

After much experimentation with different ways of powering my mini-lathe on a keep it going basis, I finally decided to go the whole hog and install an inverter and 3-phase motor to give me variable frequency drive. This is the whole story.

Eamonn Evans27/05/2020 18:16:08
1 forum posts

I am a complete newbie never having used a lathe before. I recently purchased a used Cowells lathe on eBay. It came with a motor fitted the wrong way round and runs too fast.

I have also just liberated a Kenwood Chef 375W motor complete with its speed controller which I would like to use to run the little lathe. Colin at Cowells tells me his motors are only 90W so 375W is plenty.

The currently fitted motor shaft is too large to fit the required 20mm pulley without a countershaft and of course I can't make this easily without a lathe! Also this motor has a centrifugal clutch so I am told that you shouldn't mess with the speed.

Can anyone tell me if it possible to reverse the Kenwood motor? I have bought Jim Cox's book but I am unsure.

John Baron27/05/2020 20:54:32
297 forum posts
122 photos

Hi Eamonn,

Yes you can, but you will have to feed it with DC !

I would look for a more suitable motor, maybe a defunct shower pump motor, though most of these are induction motors and are usually about 1/2 Hp. They also have an electronic soft start in them. Reversing them is simply a matter of moving the mains live wire from one side to the other side of the capacitor.

There are also some universal motor ones kicking about as well, but to reverse those you will have to swap over the brush connections. Or you could feed it with DC, which if you used a variable voltage DC supply would allow you to vary the speed as well as reverse it.

John Haine27/05/2020 21:25:10
3093 forum posts
162 photos

You can't reverse a universal (if you mean series-would commutator) motor by reversing the supply since it reverses the field in both armature and stator since the same current flows in each. Universal motors are anyway unsuitable for a lathe because they have very poor speed regulation - in theory with no load they run at infinite speed!

Tell us more about the motor that is fitted, why can't that be reversed and its speed reduced? Photos would be good.

The Kenwood Chefs that we have had seem to have a crude speed control that I suspect is based on some sort of centrifugal switch.

John Baron28/05/2020 06:22:19
297 forum posts
122 photos

Hi Guys,

The Kenwood food mixer motors change the speed by means of a stepped field winding. I don't know if the later ones use the same technique.

As far as reversing a universal motor, I did qualify that by pointing out that you would have to run it on DC ! Or modify the wiring to the brushes if you wanted to use AC.

Frances IoM28/05/2020 08:01:51
766 forum posts
26 photos
I picked up a broken classic Kenwood mixer from the local amenity site a couple of years ago - the speed control appears to be a purely mechanical control of when the centrifugal switch operates
not done it yet28/05/2020 08:02:42
4647 forum posts
16 photos

No possibility of turning the motor through 180 degrees to drive from the opposite direction?

Andy Carlson28/05/2020 08:06:16
234 forum posts
97 photos

Hi Eamonn, Hope you enjoy being a Cowells owner. Not sure I can help with the motor question but it would be nice to see a photo or two of your lathe. I'm always interested to see a Cowells and it might help others to understand your motor setup.

Andy Carlson28/05/2020 08:58:26
234 forum posts
97 photos

Just returned from my 'ideation facility' (aka shower).

A slightly different answer occurred to me... could you switch to round PU belting and run it in a figure of 8 arrangement to reverse the drive direction?

Never tried it so others may like to comment on whether it will work, but I'm pretty sure I've seen watchmakers' lathes running round belts in a figure of 8 and as far as I can see the included angle for a vee belt pulley would run a round belt of suitable size.

My Cowells vee pulley grooves are about 5.25mm at the top and my Unimat belts are 4.8mm diameter. A quick check looks plausible - they sit in the groove with a respectable gap to the bottom of the vee.

Regards, Andy

Les Jones 128/05/2020 09:02:07
2130 forum posts
146 photos

A series wound motor is a bad choice for driving a lathe as it's speed varies a lot with load. They can be reversed (Both when supplied with AC or DC.) but you need to change the internal wiring of the motor to reverse the relationship of the current through the armature and the field winding. If you supply some details of the motor that is fitted that may be a better option than the Kenwood motor.


Brian Morehen28/05/2020 18:12:42
81 forum posts
6 photos

Normal AC motors willnot work on DC Not really woth trying .

Regard BeeM

AdrianR28/05/2020 18:51:26
476 forum posts
23 photos

I have a Kenwood Chef 902, it has an electronic speed control with speed feedback via a magnet on the end of the motor shaft. The speed is varied by moving the whole PCB to/from the magnet. If yours is like that you would have to work out to extend the speed control knob to where you can reach it.

It should be possible to reverse the motor if it is the same as the 902 as the field and commutator are on separate wires.

This site has some pictures and the circuit diagram **LINK**

BTW the speed controller has a habit of failing. There are people supplying a small kit of components to fix the PCB. The kit I got from ebay also had new brushes too.


Edited By AdrianR on 28/05/2020 18:54:22

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