Shaun,

*Please* don't take this the wrong way, or think I'm being unhelpful here – but if you find wiring a motor to a fwd/off/reverse switch to be so confusing, don't you think it would be safer to ask someone more knowledgeable to do it for you? We'd hate to lose you as soon as you joined us!

David

Shaun I will agree with David. Get yourself a real professional to do the job, not an ordinary domestic wireman.

But to help you understand what is going on, your motor is an AC induction motor (AKA a ‘Squirrel Cage’ motor). These basically have two sets of winding (Coils). These are ‘Running windings’ (often called A1 and A2) and the ‘Starting windings’ (often called Z1 and Z2).

From your ‘lettering’ I think you have a motor with a centrifugal switch and a (perhaps a capacitator). The extra wire takes power to this switch which opens cutting off power to the starting windings which are no longer needed.

The Dewhurst (Drum) switch is joined to the motor by four wires (PLUS THE EARTH). In the switch there are 8 numbered screws in the switch the basic plan is as follows

Line in (brown) =1

Neutral in (blue) =3

Start winding (z1) = 2

Start winding (z2) =6

Run winding (a1) =7

Run winding (a2) =5

4 & 8 not used

AND DO NOT FORGET THE EARTH

To reverse the motor, the Dewhurst switch reverses the feed to the starting windings. So if to run the motor clockwise the switch would connect say Z1 to ‘Line in’ and Z2 to ‘Neutral in’. To run it anti clockwise the switch will connect Z2 to ‘Line in’ and Z1 to ‘Neutral in.

If when the switch is wired in and it runs the wrong way (it runs reverse when the thing points to forward there are two things you can do. The correct thing is to swap the wire into Z1 to Z2 and Z2 to Z1 i.e. swap wires to screw 2 and 6 over, but there is another trick which is to unscrew the handle and put it back in from the other side

With the Dewhurst you should have a simple stop start switch as the Dewhurst is only a reverser not a start stop unit.

rdgs

Dick

Edited By Richard Parsons on 22/04/2012 17:31:54

Hi Shaun,

Motor wiring like this is often beyond the scope of domestic electricians. I reckon that the safest thing to do would be to speak to the manufacturer of the lathe (Myford) or the manufacturer of the motor by phone or email them (perhaps with a photo of the terminal block) and ask their advice. They should be able to send you a data sheet clarifying things.

Bear in mind that it's possible that someone could have replaced the original motor in your lathe with a new motor and that this could be the cause of the confusion.

If you're really confident with motors then some investigating with a multimeter may help clarify things but this is only helpful if you're really sure of what sort of motor you've got and the characteristics of the different coils so in this case it's probably not helpful.

Will

Shaun,

If you should decide to go it alone, then you really need to bring your knowledge up to the necessary level. You should buy and study these two modestly priced books by Jim Cox:

http://www.amazon.co.uk/Electric-Motors-Workshop-Practice-S/dp/1854862464/ref=sr_1_11?ie=UTF8&qid=1335205610&sr=8-11

http://www.amazon.co.uk/Electric-Motors-Home-Workshop-Practice/dp/1854861336/ref=sr_1_12?ie=UTF8&qid=1335205610&sr=8-12

David

Shaun,

Give me as much info as possible, e.g., is it a Dewhirst drumswitch? and any names on motor, to enable me to compare with my setup. I can then tell you how mine is wired and its been going OK for years.

Regards,

John

Hi Shaun,

I think you need to find someone that UNDERSTANDS motor wiring that lives close enough to you so that you can take the motor and switch to them to identify the connections using a test meter. I have tried to talk others on this forum through doing the tests reqired to identify the connections in the past without too much success. If you live close enough to me I am prepared to try to identify the connections for you. I suspect others that have offered advice and have a profile would be prepared to do the same.

Les.