wiring southbend switch

does anyone know how to wire up the dewhirst type forward/reverse switch that goes on southbend?

look on google images and can't find one with 3 connections each side only with 4.

have only got 3 wires coming out of motor

L

N

E

cheers

Edited By naughtyboy on 02/08/2015 13:44:25

If you have only three wires I doubt it will reverse Others may know different

Roy

You need to access the capacitor wires as well. Les is yer man for this...

Neil

If you can post a clear picture of the connections in the motor connection box then it should be possible to see if it can be reversed.

Les.

all i have is short 3 core lead coming out of motor to plug.

i got it with drill press from factory that was closing down.

Drill presses are not normally reversible which is probably why the motor is not. Just ignore the 4th set of contacts.

It sounds as though you're expecting to reverse the motor by swopping the Live and Neutral, which won't work with a single phase capacitor start motor. Assuming that is in fact what you have, and that you have a conventional connection box on the motor you need to take the lid off it and identify all the internal connections. There will be 4 or 6 terminal posts inside the box - if you have 6 things are slightly easier.

What you actually need to do is to change the two start winding connections, which means bringing them out from the connection box to your Dewhurst switch (and possibly doing away with a couple of links or straps within the connection box).

If the motor is bigger than about 1/3hp you really need to use a DOL starter with NVR and thermal protection - an overloaded motor may only draw an extra few hundred watts, not enough to blow a fuse but enough to burn the motor out, hence the need for a proper starter. If you want to reverse a single phase motor and retain the DOL starter then the wiring is more complex (Below is a typical wiring diagram which shows how I wired my Boxford with a reversing switch and still retain the use of the starter - it's in the Albums section. It is specifically for the motor I have fitted so may not be suitable for just any single phase motor, so I wouldn't just try it without checking your own motor carefully first).

I think your first step should be to take a photo or two of your motor, specifically the data plate and the connection box internals, and from that you may get some more help specific to the equipment you have.

Edited By Steve Pavey on 02/08/2015 17:17:52

Edited By Steve Pavey on 02/08/2015 17:20:54

NB

You say this was a factory sale, are you quite sure there isn't a 3 phase motor fitted to the lathe and someone stuck a plug on the end to get it away in the sale? Just a thought.

As Steve Pavey says, take a picture of the motor plate, it will help everyone

Brian

Irrespective of the size of the motor you owe it to yourself to use a motor starter which gives NO VOLT protection together with overload protection as well. To reverse direction of rotation of a single phase motor you need at least 4 leads/terminals. You have to alter the relationship of the start winding to the run winding, no good just altering the supply leads live/neutral. If your motor is a capacitor start it will have a cylindrical tubular shape capacitor attached to its outer, it will be connected in series with the internal centrifugal switch and the start winding. This forms one circuit, the switch should/will be closed when the motor is stationary. That circuit is connect in parallel with the run winding, the run winding will have the lowest resistance under normal circumstance. Both are connected in parallel across the 240 volt mains supply and when the motor is up to about 75% full speed the switch opens and the motor continues to run on the run winding only. Use the rotary switch to select direction of rotation of the motor/lathe THEN press the green button on the motor starter. The Dewhirst switch is just not man enough to be used as ON/OFF the contacts burn/arc away. A motor takes a lot of current for a short moment in time when switched on and it causes the arcing. You might have to take the motor to a rewind shop and they will take it apart to see if the 4th terminal is available internally, as some one has said some bench top drilling machine are not reversible.John