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Modern reversing switch

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Ivy10/05/2020 15:34:50
52 forum posts
1 photos

Does anyone know of a UK source for modern reversing switches, the sort with a built in NRV.

Chester used to sell them apparently but they are no longer listed on the website.

Wiring instructions would be helpful too.

I am always so pleasantly surprised at the great help and brains on this site, so someone will come up with some thing I'm sure.

Thanks for reading.

Roderick Jenkins10/05/2020 16:34:21
avatar
2123 forum posts
582 photos

Tilt!

Sorry

Edited By Roderick Jenkins on 10/05/2020 16:35:22

Ivy10/05/2020 17:08:11
52 forum posts
1 photos
Posted by Roderick Jenkins on 10/05/2020 16:34:21:

Tilt!

Sorry

Edited By Roderick Jenkins on 10/05/2020 16:35:22

Lost me there!!!

SillyOldDuffer10/05/2020 17:39:52
Moderator
7562 forum posts
1680 photos
Posted by Ivy on 10/05/2020 17:08:11:
Posted by Roderick Jenkins on 10/05/2020 16:34:21:

Tilt!

Sorry

Edited By Roderick Jenkins on 10/05/2020 16:35:22

Lost me there!!!

Roderick is keeping the thread alive Ivy; sometimes questions fall off the front page and get lost in the noise. Some say 'Bump' rather than 'Tilt'. It means we don't know the answer, but think someone else will!

Dave

Martin Cargill10/05/2020 17:55:55
165 forum posts

Assuming its a single phase motor, with a single capacitor start winding, the reversing can be done with a double pole "on/off/on" toggle switch (this assumes that the wiring for the start winding is accessible and not buried inside the motor). This could be combined with a simple NVR contactor/overload for starting/stopping the motor.

Martin

AdrianR10/05/2020 18:14:01
540 forum posts
36 photos

Kraus & Naimer do CA10X pre configured as a reversing switch with power failure release. https://www.krausnaimer.com/fileadmin/user_upload/Kraus_u_Naimer/Pdfcat/KN100GB.pdf

I had a quick look and could not find them for sale, if you want one you may have to buy the switch and power failure module and assemble them. Probably worth giving K&N a call.

Adrian

Martin Connelly10/05/2020 18:25:08
avatar
1899 forum posts
205 photos

See this thread for an example.

Model Engineer Thred

Martin C

Ivy10/05/2020 18:33:28
52 forum posts
1 photos

Sillyoldduffer,

I knew about bumping, but not tilting. Thank you.

Martin Cargil,

That may be the way forward, although I would need some help with the wiring. I don't trust myself here.

AdrianR,

I will bear that in mind.

Martin Connelly,

They are no longer available.

Martin Connelly10/05/2020 18:42:12
avatar
1899 forum posts
205 photos

Have you considered separating the functions of fwd/rev and NVR? It would probably be an easier solution otherwise costs could get too excessive as you could end up going for something industrial as opposed to hobby cost.

Rockford Systems

Martin C

Martin W10/05/2020 19:00:42
901 forum posts
30 photos

Hi

What is this for, is it a DC motor as found on many hobby lathes or for an AC setup. A lot of the lathes/mills have a separate reversing switch and NVR switch. The interlocks and one pole of the reversing switch are frequently wired in series with the hold on coil of the NVR and when the reverse switch is operated and passes through the off position the circuit is opened and the NVR will trip, as will any open interlock switch.

So it would be very helpful to know what you are intending to use the setup for, a new build or an existing piece of machinery. Without any information any suggestions will be purely guesswork unless anyone knows more.

Secondly if you want help with the wiring etc. it would be good to know roughly where you are, nearest town is fine, so that should there be someone locally they might be able to drop in and advise/help.

Martin

Ivy10/05/2020 19:02:51
52 forum posts
1 photos
Posted by Martin Connelly on 10/05/2020 18:42:12:

Have you considered separating the functions of fwd/rev and NVR? It would probably be an easier solution otherwise costs could get too excessive as you could end up going for something industrial as opposed to hobby cost.

Rockford Systems

Martin C

That would do it if the combined ones are not available any where.

But again my wiring ability is hopeless, I would need simple step by step instructions. Just as well we this forum.

Ivy10/05/2020 19:06:46
52 forum posts
1 photos
Posted by Martin W on 10/05/2020 19:00:42:

Hi

What is this for, is it a DC motor as found on many hobby lathes or for an AC setup. A lot of the lathes/mills have a separate reversing switch and NVR switch. The interlocks and one pole of the reversing switch are frequently wired in series with the hold on coil of the NVR and when the reverse switch is operated and passes through the off position the circuit is opened and the NVR will trip, as will any open interlock switch.

So it would be very helpful to know what you are intending to use the setup for, a new build or an existing piece of machinery. Without any information any suggestions will be purely guesswork unless anyone knows more.

Secondly if you want help with the wiring etc. it would be good to know roughly where you are, nearest town is fine, so that should there be someone locally they might be able to drop in and advise/help.

Martin

I would like to replace the Dewhurst on my Myford ML10 to allow easy threading (I am no way an expert here).

I am in North Devon.

I have to go offline now, I will come back tomorrow.

Thanks all.

oldvelo10/05/2020 21:22:26
276 forum posts
54 photos

A Single Phase motor must come to a stop be reverse curent applied or it will accelerate back up to speed and not reverse. Yes I have done it.

Ivy11/05/2020 10:42:27
52 forum posts
1 photos

What's the collective thoughts on using a switch from ARC Eurotrade C6 lathe?

It is listed in spare parts for the C6 lathe but on the phone he would not commit to it's suitability, although it looks like a drum switch to me. (cannot paste the link for some reason) I could use an additional NRV.

I will just say it's for a Brooke Compton motor as fitted to a Myford ML10, split phase, i.e. no capacitor.

Thanks for reading again.

Bazyle11/05/2020 12:28:35
avatar
6041 forum posts
220 photos

What you need is a mandrel handle to ease threading.
If you only have a Dewhurst then you need the separate NVR switch anyway to save the contacts from burning out on the reversing switch.

The Arc switch has lots of contacts so would do the reversing job but which contacts to use gets 'interesting'. Still needs a NVR. Thanks for pointing it out it's a pretty good price so might get one for stock.

Ivy11/05/2020 13:06:04
52 forum posts
1 photos
Posted by Bazyle on 11/05/2020 12:28:35:

What you need is a mandrel handle to ease threading.

Haha, talk about being blinded by the obvious. Thank you for the best solution.

It's the "interesting" nature of wiring it up that worried me. If you get one will you let us know how fitting it goes please?

AdrianR11/05/2020 13:23:24
540 forum posts
36 photos

That switch from ARC probably would work but it is not just a case of saying 16A is enough. The 16A rating is for resistive loads. A motor is an inductive load, which gives a surge voltage when turning off. This means that switches for inductive loads have to open fast and wide to quench the spark as quick as possible.

If you look at ratings for switches they have different ratings depending on the load See this The single phase AC23A rating is probably the most applicable.

For example, my personal favourite the CA10, it is a 20A switch. For resistive loads the max single phase load of 4.6KW but for AC23A rating (Frequent switching of motors or other high inductive loads) the max single phase load is 2.5KW.

As a rule of thumb assuming the switch has an AC23A rating, de-rate by 50%. So 16A * 230V * 0.5 = 1.8KW

As Bayzle said, a mandrel handle is the real answer to easy threading, easy to make too. Motor Fwd/Rev is great, but it is the stopping at the right place is the difficult bit. All too easy to crash the tool into a shoulder.

I think there was a MEW article about restoring a Dewhurst switch, involved replacing the dewhurst with a modern one. Also there is this thread that tells you what to buy and how to wire it **LINK**

Adrian

You also have to remember about your chuck unscrewing with motor reverse.

Adrian

Howard Lewis11/05/2020 16:42:15
5320 forum posts
13 photos

Wiring just the Reversing switch is fairly simple. It is a Double Pole, Centre OFF, changeover switch.

Power (live and Neutral go to the two centre connections. The outer contacts are wired together, diagonally, with the motor feed taken from one of the outer ends.

Someone will be able to provide a diagram to show it more clearly than I have explained.

It has already been said that the direction of rotation of the motor must only be changed while it is stationary.

The NVR switch must be wired in between the supply and the Reversing switch.

It is far safer, from the point of view of both tooling and work, to cut threads by hand with a Mandrel Handle.

You crash into fewer shoulders that way!. And can feel what is going on.

Howard

AdrianR11/05/2020 17:04:04
540 forum posts
36 photos

If you can get a NVR switch that can be released by an external switch ie a 5 pin NVR switch e.g. **LINK**

And you are using a centre off switch, It is possible to wire the NVR so that if the reversing switch is moved, the NVR will drop out.

Adrian

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