View Full Version : Chinese Lathe motor question

daryl bane
09-27-2015, 07:26 PM
In attempting to convert the original dying switchgear to a simple drum switch, I have come across an unusual feature. There are two lone wires that come out of the motor housing on the fan end. If these wires are not connected together, the motor will not run, when connected, the motor runs but makes an awful racket. I figure this has something to do with the jogging feature that this lathe has/had. Is there a way to do away with this and allow the motor to function like a normal one. This is off of an Enco 12 x 36 gear head gap bed lathe from about 20 yrs ago. The motor is a 110/220 single phase induction motor. Because of the tight mounting space, I don't think any quality replacement motor will fit. Update, I figured it out , it goes to a broken contactor set, that had been removed many years ago. This had been wired to a momentary pushbutton that was pushed as the apron switch was selected, thus bypassing the original contactor function. A true bodge.

J Tiers
09-27-2015, 07:30 PM
I'd wonder if it were a thermal switch connection, except for the racket. Does the motor show any tendency to rub or otherwise make noise when hand-turned?

Is there any evidence that they might have connected to a run capacitor? Most of those motors have one.

09-27-2015, 08:17 PM
Could the JOG button have been connected to the
start windings of the motor? (like the centrifual
start switch inside?)


daryl bane
09-27-2015, 08:27 PM
Thanks for the replies. When I removed the fan shroud, I saw that the centrifugal contactor/points were missing. Probably gave out years ago. After running a trace I saw what had been done. I wish to replace the pos, but does't look like anything standard will fit.

J Tiers
09-27-2015, 08:33 PM
If the wires went to the start switch, you should be able to start the motor by shorting those, with or without start capacitor as appropriate, and then open the switch to run.

To see if it needs a start cap, measure the start winding resistance vs the run winding. If start is considerably more, it may be a resistance start/so-called split phase. If start and run are similar, it likely needs a capacitor for start, and may use one for run as well.

09-27-2015, 09:21 PM
If your start contacts are bad (or missing)
an alternative is to not use them and
instead use a potential relay, like from
the HVAC trade. They are used for self
starting phase converters all the time.


09-28-2015, 12:00 AM
You can also use a 5 amp normally open momentary push button and do the timing yourself.When you mash the button,the motor starts,when the motor starts to grunt a little let off :D That's how I used to test woodworking equipment coming in from an auction.A pushbutton and a collection of various sized star caps.

If you really want to fix the CS then Torq will have one you can adapt-


They can be bought through EIS or your local motor shop-


If the motor does use a start cap,a bleed off resistor soldered across the cap terminals helps to save contacts.

daryl bane
09-28-2015, 10:45 AM
Super thanks for all the info. Probably just use the manual pushbutton as that's what they were doing for years apparently. But the Torq might be a way to fix it properly.