Lathe - Electrical problem.

[Lockhouse]

Hi,

I've got a Boxford ME10 lathe which is about 20 years old.

We re-sited it to our new workshop about six months ago and up until today it's been working fine.

I can plug the lathe into the mains but as soon as I switch it on at the plug socket, it trips the main fuse. This is without the lathe even being turned on.

I have tried it on two different circuits and it has blown both of them so it must be the lathe that's the issue. I have changed the plug, examined all the wiring, taken the lathe mains switch off and cleaned\checked all the wires and I can't find any problems with it. Does anyone have any ideas what the problem may be bearing in mind that it trips the mains fuse as soon as it gets power?

Thanks for reading,

Andy

 

[mike 109444]

Hi Lockhouse. It sounds like you have a dead short between the live and neutral or to earth. You could meter between the live and neutral and earth with lathe unpluged! and switched off, looking for a short. If the lathe has one fitted (for saftey I would have thought so) check the zero power sense switch (built into the on/off switch?) It will be designed that in the event that the mains goes off for any reason while the lathe is running then when the mains comes back on the lathe won't start backup untill operator operates the on button. This switch will have some sort of "hold on" (till mains drops) components. The only one I have had any dealings with was fitted to a basic pillar drill and consisted of a relay coil asy that if mains droped the relay would drop and even if mains restored would still not startup drill till operator pressed on button. This relay had fried and was causing a short. Failing that meter between live and the lathe chassie and between neutral and chassie looking for a dead short.

 

[brightspark]

u say plug it in to the mains and it blows the main fuse do u mean a fuse or a minature circuit breaker or an rcd device / earth leakage circuit breaker ??

 

[Lockhouse]

u say plug it in to the mains and it blows the main fuse do u mean a fuse or a minature circuit breaker or an rcd device / earth leakage circuit breaker ??

Sorry, an RCD circuit breaker (in the fuse box).

 

[Lockhouse]

Hi Lockhouse. It sounds like you have a dead short between the live and neutral or to earth. You could meter between the live and neutral and earth with lathe unpluged! and switched off, looking for a short. If the lathe has one fitted (for saftey I would have thought so) check the zero power sense switch (built into the on/off switch?) It will be designed that in the event that the mains goes off for any reason while the lathe is running then when the mains comes back on the lathe won't start backup untill operator operates the on button. This switch will have some sort of "hold on" (till mains drops) components. The only one I have had any dealings with was fitted to a basic pillar drill and consisted of a relay coil asy that if mains droped the relay would drop and even if mains restored would still not startup drill till operator pressed on button. This relay had fried and was causing a short. Failing that meter between live and the lathe chassie and between neutral and chassie looking for a dead short.

Thanks for the reply - I'm not sure about all of it but will take this to someone that will understand more than me. The lathe electrical system has been modified in the past (by a professional) so I think I will probably end up getting in a specialist if I can't spot anything obvious. We have lots of other kit on this circuit and it is all working OK.

 

[Pete.]

If you've recently move the machine then check the lead carefully - it may have gotten pinched in the move.

 

[Lockhouse]

If you've recently move the machine then check the lead carefully - it may have gotten pinched in the move.

Cheers Pete. I've had the lathe to bits this morning.

I disconnected the internals just before the switch and it didn't blow so I , connected the live up and it didn't blow, connected the neutral and that blew it. It's definitely in the "innards" i.e. the switch onwards. I've checked all the connections and wires as much as I can and they all look OK. Time to call a specialist I think.

Thanks.

 

[Pete.]

What kind of a switch is it? I have some spare 240V contactors but they require a momentary switch to activate them.