Lathe query.

Good morning,

I am new to this site, but I am very impressed with the whole ethos and helpfulness i am seeing so far.

I have recently inherited a Town Woodhouse lathe by virtue of buying a house with it still left in situ in the workshop, and because I have always wanted a Lathe it was a no brainer to try it.

Now with the 3 phase switched on and the start button pressed it just seemed to be jammed with sparks coming out of the contactor. I have managed to get a wiring diagram for this lathe and it seems the whole machine was wired up badly and differently to the diagram, so I rewired it all to the original diagram and guess what ? It still wont start but there are no sparks now !

So I am fairly sure it must be the contactor which was why somebody had attempted to rewire it, is it worth me just buying a cheap 25 quid contactor from ebay just to confirm this, and presuming this cures my problem what make contactor would people recommend as a long term fix.

Sorry for the long post. Paul.

Welcome, Paul,

If the first couple of lathes shown on lathes.co.uk are anything to go by, you've got a nice bit of kit there. How fortunate, too, to have three-phase available in your workshop. I can't help with your firework display, but, with more information and a photo or two, there are a lot of forum members au fait with all things electrickery who will be able to sort you out, I'm sure.

John

I moved house a few years ago, but sad to say did not get either 3 ph or lathe as part of the deal !

Lucky you ! Fear not, someone here will sort out your problems.

Starter may simply be burned out. I would just buy a new unit ant take it from there.

Paul

welcome to the forum

if you have a meter check for 415v across pairs of phases on the supply side of the contactor...so you need 3 sets of 415v

then when energised check for the same on the motor side of the contacts

Ian

Paul

More info re make and type of starter and motor would help to give some advice, pictures speak a thousand words.

Emgee

Welcome Paul

All good advice above, but if you should be unfamiliar with working with it, please be aware that 415v will kill the unwary.

240v sometimes gives you a second chance but 415v is not forgiving

Apologies if you know all this.

Rod

If your garage is covered by your house insurance, it might be necessary (or at least helpful) to get the electrics checked by a qualified electrician, and a form signed saying what he checked and found OK. Unless of course you are such a bloke, in which case you ought not to need to ask questions like this.

Just a thought - its your garage and your life, after all.

Cheers, Tim

Try diconectining the motot at the motor end then operate the contactor if this operates then the fault may be your motor , There are a number of things you can try which depends on how famiilar you are with electricity and if you have a meter. ( Make Sure that all of the motor leads at the motor end are all clear and have some insulating tape round them be fore you test the contactor if you are not happy withe this idea leave alone. 3 PHASE CAN KILL

Regards BeeM

Thanks for the warm welcome and helpful replies, I would gladly post up a photo or two if I knew how to lol.

I have had the 3 phase to the lathe checked and the supply is fine, and I have checked the resistances across the windings in the motor, and they too are reading correct.

Is there an easy way to trst the contactor, either in situ or on the bench ??

.

It’s top on the list of FAQs, Paul : **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=103028&p=1

… and should probably be ‘required reading’ for any mew member

MichaelG.

Paul if you have a meter as you have checked the resistances of the windings then with the power off check for resistance on the contacts of the contacter when you press the contacts together.

then check resistance of the coil on the contactor

If you are confident with your rewiring I would obtain a Siemens contractor and overload unit rated for your motor. You will have to be careful with the selection as the contactor coil voltage maybe different to the line voltage, do you have a transformer in circuit that will reduce the control voltage? The control voltage could be anything from 24v D.C. to 240v (phase & neutral) or full 415v.

Before you buy a contractor check if there is an overload unit attached to the original unit if there is and it has tripped it will prevent the contactor closing, there will be a reset button on one side of the overload to reset it. Reset it with the power off. If it trips again the setting could be wrong, it maybe an old oil dash pot type and needs the dash pots refilled with oil or you have a fault with the motor, or the motor/head is seized and it is an overloaded motor.

Edited By Juddy on 22/10/2021 10:41:50

Mmmm I think I may have to concede here, I have a bit of electrical knowledge but not enough to guarantee I wont electicute myself, I dont suppose there is anybody more competent than me in the West Wales area on this forum who fancies the job ??

I will read up on how to post the pictures later and put some up.

Paul

Pleased to see you have seen the light, good decision if you have any doubts, some pictures will certainly assist in providing reasons for the failure.

Emgee

Before you jump into electrics, can you turn the lathe by hand?

Either at the chuck or belt /motor. It the spindle is locked you will get an electrical overload. Mis-cordinated controls could lock the spindle.

Robert G8RPI.

As Robert says, start checking for mechanical problems. BUT start at one end and work your way through.

Is the motor free to turn?

Then check through the drive train to the Chuck to see if anything is locked / seized.

It might only be an overlength bolt, an overtightened clamp, or a seized bearing.

It could even be that back gear is engaged without freeing the driven pulley from the mandrel.preventing rotation, or defect in the gear selection mechanism all owing two speeds to be engaged at the same time..

Once a mechanical problem has been eliminated then start the same logical sequence on the electrics, starting at the power feed switch, and following through to the motor feed cables..

Power OFF, use a multi meter, of course

Howard

Quite true. But the most likely scenario is that one touches a live conductor while another part of you is earthed. Nominally mains neutral is at earth potential and relative to neutral "live" is 230V. But relative to neutral each line of a "415V" 3-phase supply is ALSO at 230V. The 3 phase is 415V phase-phase voltage. So touching one of the phase wires from a safety point of view is no more dangerous (which isn't to say that it's safe!). If you connect yourself phase to phase of course it would be a different matter.

Whatever, whether 1-phase or 3-phase, mains electricity is dangerous and should be treated with respect!

Many things you can try if you have the required knowledge , if the answer is know leave alone ,Retired Electrical Engineer & Contractor . I am always very wary about offering advice on anything electrical because of the Danger part . wish you were round the corner and lived in Cambridgeshire.

Good Luck

Bee.M

Power OFF, use a multi meter, of course - as per Howard.

I say ‘Pull the fuse as well’. I put the fuse in my pocket, if apppropriate. Most circuits are protected/controlled by MCBs these days - you don’t want anyone to inadvertently switch one back on!

And if you happen to be checking mains connections while energised, please use a multimeter which is safe for those operations - many are not and some that are ‘reasonably’ safe may not be, when in inexperienced hands.

One lad, I remember, finished up on the wrong side of the room, but luckily without the crucible he was rushing to remove from a laboratory kiln at 1200C! Another was an electrician who was thrown off a gantry some 15m high but luckily landed on the side of a heap of not-too-hot clinker which cushioned his fall.

Back of hand towards possible contact points is always a good idea, along with the other hand in your pocket - less chance of grabbing hold of a DC supply or getting a shock across your ticker.

The contactor should have an operating coil and a hold coil.

I would disconnect motor belt from lathe gearbox.

Does the contactor operate from 24V from a 24V transformer-?, but of course it must swirtch 380 V to the motor.

If motor checks out ok, and contactor has no visible burning or damage, so if it operates it puts the phases in cross contact, so if contactor looks ok, I would use an insulated stick and manually push it in, if motor starts and you hold it in it runs, if this is ok, then the contacts are ok, but the operating coil which maybe 24V is faulty, or if it operates but falls out the holding coil is faulty, or the pathes involved, like a safety cct wiring.

A safety CCT broken(Switch/Wire) could then also prevent it from operating.