Lathe woes

[Horwig]

I have a Chester Machine Tools, Conquest lathe, which I think a few of us have here, or it's equivalent.

It's been miss behaving recently, "chugging" rather than turning smoothly, and sometime wouldn't start till it was turned by hand in the opposite direction.

I've checked the brushes, one is fine, plenty of meat left on it, the other one is down to about 6mm.

Can I assume that the brushes are the problem? Can't see anything else wrong with the control electronics.

Is it  normal for one brush to wear out so much quicker than the other?

Huw

[Peter Drew]

Could be that the lesser worn brush is tight in its slide causing the other to wear unevenly. You may now have a situation where the tight brush is losing contact giving intermittant drive.     

[Gina]

I think Peter's explanation is probably right.  That certainly sounds like the reason one brush has worn more than the other.  If both are free to slide I would expect equal wear and a sticking brush would give the symtoms you describe.

[Bizibilder]

Sounds like a reasonable explanation - try these folks;  http://www.arceurotrade.co.uk/Catalogue/Machine-Spares/C3-Mini-Lathe-Spares  who do spares for all the versions of this lathe (link is not necessarily for your model! (usual disclaimer).  

[Horwig]

An update on my miss-behaving lathe.

The motor eventually blew, and I took the lathe back to Chester Machine tools, who fitted a new motor, lathe was out of warranty, so £132. The lathe had very light sporadic use till January, when I noticed that the new motor behaved quite strange too, and that too eventually blew when stalled.

Anyway, Chester replaced the motor free of charge, and I got down to working out what was going on. The motor control unit is manufactured by KB Electronics, an American company, and their website had setup manuals for the board and its control pots. On looking at the preset pots, they were all in wrong positions, and they were very easy to turn, the stall current limiter for instance was at about x2.5 current, which was way outside spec. I guess the vibration over the years had slowly moved them.

They are now back to where the manufacturer specifies, and locked down with a blob of silicon, lets see if that does the trick.

 

Huw

[barkis]

I bought a 3 in 1 from Chester M T. Years ago. The one with the vertical milling machine.
I've only used it for a couple of  dovetails. Mostly machining commutators and slip rings  of Motors and Generators.
Been a good servant, and only a couple of the Plastic Guards have broke. Needless to say, I have not replaced them, which is silly really.
I should do.

[Stub Mandrel]

5 hours ago, Horwig said:

They are now back to where the manufacturer specifies, and locked down with a blob of silicon, lets see if that does the trick.

It's the voltages/currents that matter not the angular positions.

There are websites that give chapter and verse on setting the pots.

You can also test the boards using a light bulb (filament type) to avoid damaging the motor.

[Horwig]

12 hours ago, Stub Mandrel said:

It's the voltages/currents that matter not the angular positions.

 

Totally agreed, but when their position doesn't match what's marked on the setup manual, it don't half give a clue that something needs doing.