New lathe 'misfiring'

Hi all,

I hope someone can help, I've only owned my Chester DB8 lathe about 8 weeks but this morning it's started running erratically like car misfiring particularly at low speeds.

At higher speeds the speed seems more constant but the machine shudders, my initial thoughts were it appeared to be an electrical rather than mechanical fault but I'm not certain.

It worked fine yesterday and hasn't had any rough treatment today although for the last day or 2 the cuts I make seem to have had a poorer finish

Thanks

Peter.

Peter

If its a brush motor check for sticky brushes, well known fault on Chinese gear.

That was my thought two, one brush can stick and the motor runs irratically. Also the sparking softens the spring and melts the copper wire or its solder

Thanks guys,

If it helps any more, I've just fired it up again and it wouldn't start turning till I turned the speed potentiometer to about 1000rpm. Once it was turning I could lower the speed but it was very erratic.

If it is only 8 weeks old it is still under guarantee. Have you talked to Chester?

Mike

Thanks guys, I've solved the problem at least for now and you've made 1 man very happy

It was a problem with the brushes as you suggested, one was worn far more than the other and the contact wire that run through the springs were in a poor twisted shape.

I've straighted out the contacts, and given things a bit of a clean and it works fine now. I'll order a new set of brushes / springs etc from Chester on Monday but the repair I've done for now should tide me over for a few days.

What initially I thought looked like a disaster actually turned out well, it gave me chance to familiarise myself a bit more with the machine and generally check a few things seem to be running ok.

Mike, you are right it will be under guarantee but I thought I'd ask here first in case it was a job I could fix myself as was the case. When I speak will Chester I'll see if they send the spares free, if not I'm not going to haggle over a few quid, I'm just happy it works ok.

Here's the state of the brushes :-

Thanks

Peter.

Peter,

You have the generous nature of a Saint.

... I would have been furious.

MichaelG.

Cheers Michael, I kinda was furious at first till it became apparent the problem might be simple to fix

On slight snag tho, I've put the brushes in the other way so now to operate my machine normally I need the switch in reverse !

I can't be bothered stripping it down again when I'll probably changing the brushes completely in a few days so I'll just live with it for now.

I suspect it's been running very slightly erratic for a few days before becoming visibly noticeable, I've recently had trouble getting good finishing cuts but put that down to my inexperience, no matter what speed / feed / tool etc I tried something didn't seem right. I've just tried turning a piece of steel as a test and it's fine now.

Peter.

Just read this post and went out to do a bit gentle turning and my WM250 is now just the same. Made a couple of cuts then speed varied and did not sound like a happy chap. Off and on and now reluctant to start. I'll be on some new brushes on Monday from Warco. Perhaps worth getting a second set - then it will last 20 years! SteveW

Nick, you did not need to remove teh whole end from teh motor, there are should be two large caps with a coin slot that can be unscrewed to remove the brushes.

Steve, I bought two sets when mine went but have not needed to change again after a lot of use. But a sthey don't cost much its worth ordering the spare set just incase.

Hi,

Jason I did initially try removing the slotted covers but they were solid, once I took the end off I took the brushes out then the covers were ok, I reassembled it through the covers.

When I order new ones do they normally come as a complete set with the springs and contact wires ?

Peter.

Yep

Can I suggest contacting your local motor rebuild company and see if they have a better quality brush as the Chinese ones are very coarse and leave dust all over the motor inside which then causes tracking and trip problems.

On such a new lathe the difference in brush length is bad, unless you have used it for 200+ hrs ! Also the shorter brush does not seem to be rectangular. I think the problem is deeper, is the brush holder OK? Also the springs seem excessively "thick" i.e. excessive contact pressure.

You can use any (larger) mains type brush providing you can use or fettle the spring and contact . They "sand" down easily with sandpaper, though a rather messy job to do.

FWIW I have just changed the brushes on my Black and Decker electric drill, one was down to 1mm thick the other about 3mm, not bad after 46 years!, and yes it gets used a lot., 1000+ Hrs by now.

Frank

Hi Frank,

Thanks for that, I think before I do anything drastic I'll order a new set of brushes from the supplier and compare what they send with what I have now.

The springs in the first picture aren't from my machine.

Peter.

Hi all,

Just thought I'd say I rung Chester this afternoon and Tony who I spoke to and bought the machine off at the Harrogate show saw this posting and has already kindly put a set of brushes in the post before I'd even called them.

Full marks to Chester for customer service, it's little things like that which mean I'd be more than happy to buy from them in the future.

Many thanks Chester.

Peter