Hi Lynne

If it has never worked correctly it could be wrong connections in the fwd/rev switch, is the NVR switch fitted in the line from the fwd/rev before it goes to the motor or starter if you have one fitted.?

Emgee

Is the NVR and reverse switch an integrated unit or are they two separate switches? I have never come across an integrated unit. Normally the NVR is on the mains input and the forward/reverse switch is on the output from the control board and just swaps over the positive and negative lines. So changing direction should have no impact on the NVR switch.

Peter

What sort of Lathe ? What Sort of motor ? AC or DC brush or brushless ! NVR MUST be before the reverse switch ! Has this just happened ? what sort of Forward and reverse switch do you have ? As always pictures will be a big help ! Noel

The symptoms suggest to me that the forward/reverse switch has failed. Either the Reverse contacts have broken, or maybe a wire has vibrated loose and broken the reverse connection.

On my machines the switches have always been mounted on front panels that can be unscrewed and lifted off to see the wiring or change the switch. A dangling connector should be obvious, and is generally an easy fix. Otherwise, the F/R switch can be replaced : they're not difficult to source. A photo would help identify it.

Which machine is it? Someone might have a circuit diagram.

Dave

SOD

The OP implies that the machine still runs in reverse but the NVR doesn't latch so the start button has to be held down for it to run.

This suggests that the forward reverse switch itself is sound but there is no power being supplied to the NVR coil in reverse. So, as I suggested in my previous post, reverse is operating in jog mode.

Connection issue with the NVR unit either internally or, if it is intended to have a jog mode connection, externally.

Assuming its one of the inexpensive import NVR units similar to the one I linked to above, best to simply change the unit if its not an obvious external connection failure.

Personally I'd swop for an industrial rated system like that in my second links. The interlocked contactors can be found more cheaply. Think I paid around £40 for mine and £15 (ish) for the button box. Roughly double what a the common import unit costs so not scary out or reach.

But I dislike the compromises often inherent in affordable equipment and can afford to indulge that affectation. Which many folk can't.

Clive

We know now this is Myford Lathe My thoughts are that some contacs in the NVR control are either worn or require cleaning also is this working on 3 phase or single phase . Lack of info is giving rise to a load of unneded answers.

More Info Please

Bee M

The last time I enquired about a price for a similar switch for an Emco Milling machine cost was £94

Is there a part number showing on the switch ? if so a replacement could be sourced.

Emgee

That switch stack looks fairly open, you could try a blast of compressed air.

If hyou have a Poundland near you you can buy a aerosol Air Duster for £1.00. This is worth a try I use these very often for quickness.

Regards Bee.m

After looking at the pictures in your album I am not convinced that it is an NVR switch. Start the lathe in the forward direction. Switch the power supply off to the lathe. Did the switch return to the centre off position ? Restore the power to the lathe. Does the motor start as soon as the power was restored ? These tests will show if it is an NVR switch.

Les.

Lynne

A quick Google turns up the official 2021 Krause & Naimer short form data on the cam switch range at **LINK** https://www.krausnaimer.com/fileadmin/user_upload/Kraus_u_Naimer/Pdfcat/KN120GB.pdf .

From your pictures the switch you have seems to be a standard blue-line cam switch. These things can be built up in myriads of configurations by combining switch blocks, actuating units, control levers and position indication plates. Just a matter of flogging through the various codes for each part to get the device you want. (Headache pills and a wet towel round your head probably essential if starting from scratch.)

Looking at page 6 it appears that the code for a no volt release actuator is CG8X which mates with an S0 size switch. I see no reason why the actuator can't be ordered as a separate unit and replaced. Having changed switch stacks on a similar unit, albeit without no volt release, on my Bridgeport I can confirm that they come off and go back quite easily. However its unwise to remove the connections as figuring out what goes where can be a problem. I had no choice as mine had been bodged round burnt out contacts!

If you decide to order a complete unit it seems like you have a double throw switch with 60° switching angle.

Page 23 shows specific motor reversing switches. Alternatively it could have been built up from switch sets as shown on page 11 where there is a choice of plain centre off or electrically isolated contacts.

Hopefully the codes on the switch bodies are still visible so ordering a new complete unit shouldn't be too hard.

But I'd just change the actuator which ought to be part CG8X. Assuming you have an S0 size switch, easily sorted by measuring as its a bit under 2" square.

Really this is something that the UK agents should be almost instantly aware of. But I didn't find them technically knowledgable in the past. Problem is that, so far as I can see, UK stockists tend to hold build up units in the common varieties rather than getting involved in build to order.

Assuming a 3 phase motor I think part code CG8XA401 be yours. Have to take it apart to figure out the panel mounting system. Probably 4 hole without the escutcheon plate, yours doesn't look to be standard K&N.

Hope this helps.

Clive

Edited By Clive Foster on 06/11/2021 13:09:44