Chester Conquest Super Mill Potentiometer

[pvmParticipant @pvm]

Hi anyone know how to check my potentiometer fully, I have watched  many YouTube videos , but they never mention

my type of 4K potentiometer , I have checked resistance on the three terminals they are fine + 4.5 k – 4.5k

but I don’t get any readings using multi meter from the two terminals which i assume is the switch ,I tested  it

with a bell it rings with switch on or off all the time ? maybe this how it works ,I just would like to know whether

this is a fault or not I contacted Chest Machines for a new one but the never got back to me . Euro Trade did offer

a new one that is similar to my machine ,this may be my only option . PVM

[BazyleParticipant @bazyle]

Can you post a photo of the switch just to make sure we know what we are talking about.
The switch should make an audible click as it operates.

[pvmParticipant @pvm]

Thank you for replying ,I will post photo tomorrow, However  the potentiometer is just a standard pot with a switch located below main pot , Yes it does make a audible click when turned anti clock wise ,which is when you reduce spindle speed to zero and switch makes audible click, Not when turned clock wise to start spindle rotation.

My question is should there be continuity from one switch terminal to the other terminal when the pot is turned clock wise or anti clock wise before pot range end is reached.

[John HaineParticipant @johnhaine32865]

Usually at full CCW the switch is turned OFF (no continuity)

[pvmParticipant @pvm]

Has requested here is the attached photo of my Potentiometer from Chester Conquest Super Mill:-

[pvmParticipant @pvm]

Thank you for your advise John , However I seem to be going round in circles here .I just want know if there should be continuant between the two switch terminals when the switch is turned on i.e.  potentiometer turned clock wise If the answer is yes then my potentiometer is faulty and I will go ahead and purchase a new one .

 

 

 

is faulty

[Michael GilliganParticipant @michaelgilligan61133]

[pvm]

On pvm Said:

[…]  Yes it does make a audible click when turned anti clock wise ,which is when you reduce spindle speed to zero and switch makes audible click, Not when turned clock wise to start spindle rotation.

My question is should there be continuity from one switch terminal to the other terminal when the pot is turned clock wise or anti clock wise before pot range end is reached.

I struggle to understand how there can be no audible click when the pot is turned clockwise, but it certainly suggests that the switch has failed.

From the crude diagram supplied by Chester, it looks like you could easily confirm that by substituting a known good switch.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[Robert Atkinson 2Participant @robertatkinson2]

The two contacts on the black part of the pot/switch assembly should show continuity when the shaft is anywhere but fully counter clockwise.
It appears yours is faulty.

Robert.

[John Haine]

On John Haine Said:

Usually at full CCW the switch is turned OFF (no continuity)

The one on my Chinese lathe is the opposite: It is ON when fully CCW and OFF (no continuity) in all other places. It’s *possible* that the OP’s could be the same.

Whatever the case, it should go from open to closed or vice-versa in the fully CCW position.

[pvmParticipant @pvm]

Thank you Andy mine is faulty then I will order new one

PVM

[pvmParticipant @pvm]

Thank you Robert mine is faulty then, I will order new one

PVM

[pvm]

On pvm Said:

… I just want know if there should be continuant between the two switch terminals when the switch is turned on i.e.  potentiometer turned clock wise If the answer is yes then my potentiometer is faulty and I will go ahead and purchase a new one .

 

 

The simple answer is 99.99% yes, and switched pots are so cheap you might just as well change it.

Though Andy reports his lathe is different, that’s highly unusual, not least because these machines use bog-standard pots to keep the price down.  Special components are the province of high-end kit, where money is no object.

For completeness:

 

Dave

 

[pvmParticipant @pvm]

Thank you Michael for your answer. However that is the reason I am asking the question to save me purchasing a £16 pound potentiometer that i may or may not need .Now I have got a clear answer to my question I can go ahead and order a new pot.

PVM

[pvmParticipant @pvm]

Thank you SilyOldDufferfor for your reply .However surprisingly a new  potentiometer to replace the one I have are £16 inc post, Which is a concordable amount just to prove the original was fault. Now I have got the correct definition

to the functioning of the potentiometer in question I will go ahead and order a new one . So thanks again to all the replies to my post. Which confirms how helpful Model engineering forums are.

PVM

[John HaineParticipant @johnhaine32865]

https://www.amazon.co.uk/4K7A-Rotary-Switch-Potentiometer-Linear/dp/B07YVBMBBX

 

[pvm]

On pvm Said:

Thank you Michael for your answer. However that is the reason I am asking the question to save me purchasing a £16 pound potentiometer that i may or may not need .Now I have got a clear answer to my question I can go ahead and order a new pot.

PVM

Sorry … some miscommunication !

I was suggesting you could CHECK whether the switch was dud, simply by substituting another switch [or maybe even just twisting the wires together].

All of this using the existing potentiometer.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

What have you ordered PVM?   An ordinary switched 4K7 linear pot for your purpose is typically about £5.    £16 suggests something better than needed like a high-end audio part, or maybe mildly unsuitable, like a multi-turn pot.

Dave

[Andy_GParticipant @andy_g]

Arc Euro give the part numbers for both contacts open when off and contacts closed when off for a similar machine (not necessarily an exact equivalent):

Link

“There are two possibilities available depending upon which speed control board is fitted. The correct pot should be identified either from it’s own label (if present), which speed control board is fitted to the machine or by the switching operation (if working).”

 

Code / Potentiometer Label / Speed Control Board / Switch Operation

SX1-124A / WH24-2 F4k7 / FC150BJ / Contacts Closed when switched off
SX1-124B / WH24-2 Z4k7 / XMT2315 / Contacts Open when switched off

I don’t know if any of those codes correspond to either the pot or the speed control board on your machine.

 

(I did find a better quality replacement for the ‘contacts closed when off’ option – which is a rare beast. Let me know if you want the details.)

[pvmParticipant @pvm]

Thanks Andy for the codes which could be really helpful and thank every one else for their contribution on my problem   re Potentiometer.

I have already made some enquiries to Arceurotrade and my original supplier Chester machines Tools with all info gathered here .My Chester contact has proved difficult ,He said he would investigate if they had any in stock

I had no reply for about a 3 days on contacting him again he said sorry but advised he was off for a few days, but promised to pursue the investigation further ?.

Arceurotrade were very helpful and said they had a similar Potentiometers but like you have pointed out they need to know which version I require.

So plan A  Is to wait it out with Chester Machines to see what they come up with , and hopefully purchase new pot.

Plan  B       With information gathered here purchase from Arceurotrade

Plan  C       I have already made a beginning for plan C by purchasing  a three phase motor from internet in the                         event A and B fail.  I will then convert my mill to three phase drive using one of my inverters . I am sure                   down the line the existing drive system will fail.  I will keep you informed of the outcome has it                                 materialise.      PVM

 

 

[Andy_G]

On Andy_G Said:

Arc Euro give the part numbers for both contacts open when off and contacts closed when off for a similar machine (not necessarily an exact equivalent):

Link

“There are two possibilities available depending upon which speed control board is fitted. The correct pot should be identified either from it’s own label (if present), which speed control board is fitted to the machine or by the switching operation (if working).”

 

Code / Potentiometer Label / Speed Control Board / Switch Operation

SX1-124A / WH24-2 F4k7 / FC150BJ / Contacts Closed when switched off
SX1-124B / WH24-2 Z4k7 / XMT2315 / Contacts Open when switched off

I don’t know if any of those codes correspond to either the pot or the speed control board on your machine.

 

(I did find a better quality replacement for the ‘contacts closed when off’ option – which is a rare beast. Let me know if you want the details.)

Well I never!  In a lifetime of messing with potentiometers I’ve never come across one where the switch closed in the off position.  Yet here it is, a real live Unicorn!  Amazed a Chinese lathe would contain an unusual component like this.

littlemachineshop explain:  This speed control potentiometer works an mini lathes and mini mills where the part number on the circuit board begins with FC. It has a switch on the back that is used with the emergency stop switch on some mini mills and mini lathes. If your machine doesn’t have an emergency stop switch, simply ignore the switch contacts.  …  Use this potentiometer with motor controller boards where the part number begins with FC.

I’m always banging on about the danger of jumping to conclusions based on past experience, and here I am, hoist by my own petard.

Most educational this forum, and many thanks to Andy for rocking my world!

Dave

[Grindstone CowboyParticipant @grindstonecowboy]

Back in the days of Maplin, Stevenson, etc., I seem to recall that some pot switches could be changed from NO to NC in the fully CCW position by some fiddling about with a little fibre cam. Or I may be imagining it.

Rob

[SillyOldDuffer]

On SillyOldDuffer Said:

Well I never!  In a lifetime of messing with potentiometers I’ve never come across one where the switch closed in the off position.  Yet here it is, a real live Unicorn!

It was a first for me too. 🙂

For posterity (since I’ve just found the info), a better quality pot for the ‘closed when off’ option is a Bourns model 56 Series which can be obtained with an SPDT switch.

Part numbers:

5k ohm (or 4.7k) Bourns 56AAD-C28-B13/R81L

10k ohm: Bourns 56AAD-C28-B15/R81L

I couldn’t find a UK supplier for single quantities of the B13 (5k) pot, so went with the B15 (10k) pot as I was pretty sure it would still work. (It does).

The 10k pot is available from RS Components it was about £12 four years ago, but I now see it’s £24!!

https://uk.rs-online.com/web/p/potentiometers/7422198/

Mouser seem to carry it too, but also pricey:

https://www.mouser.co.uk/ProductDetail/Bourns/56AAD-C28-B15-R81L?qs=QpZVHcK7GhTE0BqrfbGLYA%3D%3D

Other variants to look out for:

5th character ‘A’  OK (anti rotation lug)
7th character ‘B’ OK (smaller shaft diameter)
8th/9th characters 24 OK (shorter shaft)
11th character ‘E’ OK (electrical tolerance)

It is a much, much better quality component.

Old and new:

NB! This may or may not be relevant to the Chester conquest mill.

[pvmParticipant @pvm]

Thanks to all shown hear that gave good advice on my problems with my Chester conquest mill

Andy , Rob , Dave, Michael , Robert and John:- This post is a follow up has promised.

I purchased a new potentiometer from amazon to see if that was the problem, However it did not solve the issue.

So I bit the bullet and proceeded with plan C  ” Convert my mill to three phase drive using one of my inverters .which I had and purchase earlier. I then purchased  a new 3 phase motor form ebay .and installed it onto my Chester Mill . The result worked perfectly Please see phots included:-

 

[Author]

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