Myford motor reverse switch ML 10

[Lathe User]

Morning. I would appreciate some advice on the following please.
The Dewhurst & Partner Ltd of Hounslow TypeA Forward Off Reverse switch from about 1970

This switch was fitted to early Myford ML10 as standard equipment to control a single phase motor using 4 cables + earth between the two. I have a short!
I am fixing the lathe to sell. during its decades of storage I am told a baulk of timber fell on it bending the top slide and cross slide feeds. These have now been replaced with new Myford parts.
The above control had its tin casing bruised. On taking it off I was more than a little surprised that the centre stem of the control pivots on the bottom plate. Removing the front cover dislodged the stem and parts of the switching stem just fell on the floor.

Now the question is - have I re- assembled it right or is it the connection to the motor I have wrong - or both?
A diagram would be brilliant.

A second question is - is there a modest modern equivalent you could guarantee will do the job. What exactly?

 

[clogs]

as I understand it there is no similar switch.....
for further info look at modelenginner forum uk.....
if u need a switch theres prob one around.....
a lot have got the 440v route with a VFD.....

also I beleive lathes uk have wiring diagrams and manuals for free.......
hope this helps.....

just wish u could get a norm 240v motor to go in reverse....??????

 

[ChaiLatte]

Wiring and assembly:

https://misterlinnsworkshop.wordpress.com/2014/03/08/dewhursts-big-switch/
Modern alternative:

https://www.stationaryengineparts.com/Electric-Motor-Reversing-Switch.html
(switch is generic Chinese, so will be available from other vendors).

 

[Spectric]

just wish u could get a norm 240v motor to go in reverse....??????

If it is a cap start motor then reverse the starter winding, only problem is finding the two ends which might be burried in the windings. This might be what Myford have done with four wires, two run winding and two start winding. Why not a reverse in the gearbox like some colchesters.

 

[ChaiLatte]

just wish u could get a norm 240v motor to go in reverse...

Non-reversable single phase motors are the exception rather than the rule.

Track down a copies of Jim Cox's book 'Electric motors' and his imaginatively-titled second work 'Electric motors in the home workshop' (available on the Internet Archive), read, digest and all will become clear.

 

[JEC]

Does this help?

 

[Spectric]

Not unless you show where the wires go to or are taken from.

 

[Lathe User]

Does this help?

Yes it most certainly does- thank you.
Presently
T1 I have live
T3 neutral
T4 & T8 blank

So the other4 are to the motor of which T5 goes to AZ (Black)
T7 goes to A. (Black)

Leaving me according to the drawing, if I have understood it, with the two that alternate with the switch.

T2 to an unmarked winding (red)
T6 to 7 (red)

Further more, if I have understood the drawing when I unhook everything from the switch I should only get continuity between T1,T5 &T6

And T3, T2 &T7 when in forward position

But I am getting continuity withT1,T5T6& T2!
And no link between T3T7

Reverse fails similarly
Off is fully isolated

So maybe the question I should be asking is “has anyone any experience/ information about rebuilding the bottom end of the switch where it fell apart? Please!

 

[Myfordman]

Extracts from ML10 and ML7 manuals relation to drum switch wiring

 

[Lathe User]

Extracts from ML10 and ML7 manuals relation to drum switch wiring
View attachment 148953
View attachment 148954

Thank you very much for taking the trouble, that’s another piece of the puzzle in place. I now know I have the connections between the motor and switch correct. Obviously my motor terminal “7” was really “Z” thought the nomenclature was odd !

Having thought some more on the drum switch, I think, all I really need to know is the placing of the silver links between the bars in the switch.
I have link across 1 & 5, 2 & 6 and 4 & 8. I am coming round to the idea that the 2 & 6 should be moved to 3&7 can anyone confirm this please?

The silver is clear on the fourth connector but the first two are dull and the third missing.

 

[Myfordman]

On my drum switch counting from the front, the silver bridging contacts are on 1st, 3rd and 4th switch sections. Difficult to photo but you might be able to just see the bridges.
Switch viewed from the right hand side so front of switch is to the left of photo.
Ignore the lack of wires on mine it’s simply controls an inverter and not a motor directly.

 

[Myfordman]

Just checked the obvious.
Loads of youtube videos on these switches as they have a bit of a cult following.