View Full Version : How do I wire my motor? ML7

05-23-2012, 06:16 PM
I'm trying to wire up a motor for my Myford ML7. The motor itself is a Crompton Parkinson 1/3hp with resilient mount. I realise it is a bit too small for the job but it's what I have available at the moment untill I can get another. The motor has four terminals and earth.
The top three are labeled A, Z and AZ. The bottom terminal isn't labeled. There is an obvious earth on the casing below the terminals. The cover plate says to connect the mains terminals to A and AZ so
I connected live from the mains to A and neutral to AZ. This allows the motor to run but only when I spin it up by hand.
Reading the ML7 owners manual, I found out that there is starting wiring and running wiring in the motor. Can anyone tell me how to connect the motor so that it starts and runs? I don't have a reversing switch so it only needs to run in one direction. Do I need to bridge across some terminals in order for the motor to start?

I have a couple of pictures of the motor but I don't know how to post them on this site. Can anyone help me with this also?

Many thanks


05-23-2012, 06:39 PM
Sounds like you're on my side of the pond, and you have a single phase capacitor start 240 volt motor.

You probably need to wire a starter capacitor between AZ and A for one direction, and between AZ and Z for the other direction. A capacitor doesn't have to be precise, but it has to be a motor start type of capacitor. It'll be three inches longish, and one 1/4 inches diameterish. Any good electrical wholesalers should have some in stock. Even if you don't know the correct value, any old value will get you going. Try googling for how to calculcate the right value.

But officially, if you don't know what you're doing, get a pro to do it. Oh, and don't stand in a bucket of water while you test it.

For pics, there's a sticky at the top of the list, that says you've got to put your photos somewhere (Photobucket, Flickr, your space on your ISP's disks in your webspace etc) then reference them with [img ] commands. Easy once you've done it. A pain the first time.

John Stevenson
05-23-2012, 07:10 PM
Martin, there is a Yahoo group for Myford owners and it has a lot of information in the files section.
first posts are always moderated to keep spam out and after that you are free to post.


BTW the 1/3 hp motor was standard on early ML7's. I had one for years and it wasn't a problem on power, the belts would slip first.

05-24-2012, 06:31 AM
A capacitor doesn't have to be precise, but it has to be a motor start type of capacitor.

I tend to fit a motor RUN capacitor, they're continuously rated rather than intermittent. There's little or no difference in cost these days.

J Tiers
05-24-2012, 09:19 AM
A single phase motor always has some sort of second winding to get it started. This second winding is generally disconnected by a switch as the motor comes up to speed. The start winding may have a capacitor in series, a resistor in series(very old motors), or it may be wound with different thinner wire, as with the so called "split phase" motors.

The motor is reversed by reversing the connections of the start winding, which will cause it to start in the opposite direction (but will not reverse it while running). While you don;'t need to reverse it, you Do need it to start in the correct direction.

There is another type motor which does NOT disconnect the "start" winding, that winding is used all the time. That type uses a capacitor in series all the time, but it is a special type intended for continuous use (not just starting).

if you don't find help at the Myford group, perhaps posting some pictures of the winding and of any data plates or diagrams will help us determine what you have and what to do.

BTW the 1/3 hp motor was standard on early ML7's. I had one for years and it wasn't a problem on power, the belts would slip first.

I have a 10" Logan with a 1/3 HP motor.....the newer 3 phase motor that replaced it yeas ago is actually not even a continuous duty motor, but it has never been a problem.

As JS says, the belts generally slip first. I have never stalled the motor.

Same for the 1/4 HP motor on the small mill..... even running large slabbing cutters, the motor has never stalled. I push the thing, so it isn't a case of "dusting off" material....

05-24-2012, 02:19 PM
Hello again.

I've loaded up some pictures (below). Hopefully I have got the resizing right. I wonder if this helps at all. I can't see any evidence of a capacitor having been fitted and when I got the motor off another ML7 it had red wires connected at Z and the bottom unmarked terminal. A and AZ had black wires attached. I not very good with all things electrical so I was wondering if there was a reasonably simple way of wiring this up for use in one direction only.

Many thanks





05-24-2012, 03:30 PM
Just do as it says

mains on A and AZ

put one of the others on A and the other on AZ

link AZ and F bottom one

and Link A and Z

if it gus round backards swap A and F

as it ses on the tin

these do not use a cap they have a cenrif switch inside


05-24-2012, 05:01 PM
I have connected the motor as Stuart outlined above. It starts and runs but its running in reverse. I wonder if you could outline in idiot terms how to reverse it.



05-24-2012, 06:44 PM
I've managed to reverse the motor with the advice above.
Many thanks to all.


05-25-2012, 03:33 AM
well done

just dont poke your fingers in when its got power to it .it will bite :-)


05-25-2012, 07:27 AM
here's my brooks crompton motor wiring ...3/4 hp south bend model 9a

it appears to have different numbers and letters to yours ....anyway ..if not relavent to you, will be relevent to someone else ...every little helps

this diagram i made out when i did it ..sadly i remember things for only a couple of months after ive done something ..this was done over 4 years ago

i had to wire mine to a reversing switch .

you may need a reversing switch ..as you will find it difficult to cut metric threads without .

when threading ..on an imperial machine ..metric threads ..lathe has to be kept in threading mode ..and reversed back in threading mode, to the start of a thread.


label on cover


i wired my reverse switch an unconventional way after ...

i wanted to have one control station stop/start and reverse ..for two machines .....a lathe mounted amolco mill and the lathe ........so i made up a seven wire heavy duty cord with a car trailer plug on it .

all the best.markj