Good morning John, if I remember right this is a blue cam switch, with a three position knob on the front of a silver fascia plate. I've just tried to lift a picture out of the K & N catalogue but it only comes as a pdf which I can't put in an album.

It's some while since I had one of these switches to pieces, but I think that the detent mechanism is behind the switch fascia, There is a nylon cam and a spring which controls whether the cam mechanism stays put or returns to centre or what, and it sounds as though this has failed or got worn out. Whether it is repairable is a whole different can of worms.

Don't take the black switch body to pieces – there is any number of little bits of brass and things hiding in there waiting to jump on the floor.

If you want to have a go at the detent mechanism take the knob off the front by loosening the little screw in the centre of the knob, don't undo completely it's only a clamp, then pry the silver fascia out of the black surround at the front of the panel. This exposes four screws which mount the switch to the panel. Undo them and push the switch body off the back of the panel. Now you should be able to work out how to take the front off the switch cam to see the detent mechanism. The down side of this of course is – quite apart from the intricacies of getting to this point – it may not be obvious what is missing.

Last time I tried this I managed to get it to bits but gave up trying to put it back together, I needed more hands than an octopus. You'd be better off buying a new one, but be careful to specify the right thing as they all look the same on the outside, but the arrangement of the internals is crucial. I think City Electrical Factors are agents for K & N.

Alternatively this looks like the right thing, **LINK**

and at least you know where you're starting from. I would think you want the 2 pole changeover for a single phase reversing switch so that looks like option CO202 (20 amp 2 pole). It may not be obvious how to connect the new switch to the old wiring, it should come with a diagram which describes what to do.

Good luck, and all the best Simon

Assuming that the switch is goosed and at the risk of upsetting the electricians, for a cheap solution, why not just a 13 amp plug and switched socket?

The reversing function is not very useful on a Myford 7, potentially a liability  with the screwed mandrel nose. (How do I know when I've got a Boxford? That's the reason for the only mark on my lathe bed.)

Edited By Clive Brown 1 on 22/12/2018 15:53:20

Edited By Clive Brown 1 on 22/12/2018 16:01:35

Hi John,
I have had another thought. If there are any interlock switches on a chuck guard or cover over the belts or anything else they would be wired in series with the NVR coil. If there are interlocks it would be worth making sure that they show continuity when closed. Is it possible to get the switch out of the box so we can see the underneath of it ? I expect there to be two wires going to the black part at the front of the switch. If there are can you measure the resistance between the ends to see if the NVR coil is open circuit ?

Les.

John

After a Doctor visit this morning can manage to do this myself without too many shakes, so have taken a pic of my switch which seems the same as yours. Pics below

If you check out the items noted by Les Jones, who is a whizz at this electrics lark, and still need a replacement, then let me know.

I will send you a message with my email address, pick up the message from your Inbox at the left hand of the green bar at top.

John

Better but not fixed! Still have a job getting the screwdriver blade into the slot without using 2 hands.

I am supposed to be getting rid of any stuff not actually needed, so the switch can go and start a useful life.

Back in the day I used to repair Myfords, usually switched with the dreaded Dewhurst rotary, and owners were very keen to have those renovated rather than replaced with one of these vastly superior switches. I haven't seen one of these for a very long time.

If you open the message I sent we can sort out the details by email rather than in public. It won't cost you a lot

I have the exact same switch and the exact same problem. Is there a chance someone can tell me which switch I need to replace mine please?