Lathe motor issues

[Packhorse]

I have a problem with my lathe.

It has been slow to start for quite awhile and I need to spin the chuck to get it running at normal speed when I start it cold. I put this down to a faulty starting cap.

I was using it yesterday for awhile and it had warmed up to normal temp and would start fine. But when I went to reverse the motor to use the mill it wouldnt run. Instead it just made a loud humming sound. It still ran in forward though.

The reversing switch felt a bit sloppy so I brought another and swapped it out.
This didnt help.

Any ideas? Yeah I know I should have changed the starting cap ages ago.

 

[gt40]

Check the centrifugul switch. I had similar issues with my Jet.

 

[precisionworks]

The starting cap & the centrifugal switch are the two most common problems on a 1ph motor. But ...

Start windings sometimes go bad and have either a open spot or a grounded spot. If replacing the cap & switch don't help, it's usually cheaper to replace the motor than to rewind it ... unless the motor has some type of special mounting configuration, or it's a 2-speed motor, etc.

If you do have to replace the motor, this is a great time to consider a VFD conversion.

 

[Atlascycle]

The starting cap & the centrifugal switch are the two most common problems on a 1ph motor. But ...

Start windings sometimes go bad and have either a open spot or a grounded spot. If replacing the cap & switch don't help, it's usually cheaper to replace the motor than to rewind it ... unless the motor has some type of special mounting configuration, or it's a 2-speed motor, etc.

If you do have to replace the motor, this is a great time to consider a VFD conversion.

Geesh Barry you would think that you get a royality off of every VFD that is sold

Jason

 

[archer6817j]

I have a pretty lengthy relationship with a motor and your exact problem. So far everyone is right. Centrifugal switch points getting stuck or failing capacitor are the most likely.

You may also consider soldering a MOV (metal oxide varistor) across the switch contacts. I'm not an EE but it was recommended by one. What size capacitor is a bit of a guessing game. I have some unused ones that I'd be willing to send you for free. They worked on my 1hp motor but I chose them by trial and error. However, I haven't had the points stick in a couple of years.

I tried everything else and nothing worked consistently. Incidentally you can disassemble the motor and visually check for welded points. Another thing to note is that the problem will be less frequent if you leave the lathe at a high RPM setting that needs less torque to get started and hence less current inrush while the points are in contact (before the centrifugal force separates them). Not very practical in practice.

Eventually I went for 1.5 hp baldor motors and a VFD so I can second that. If you can afford it, it will change your machining life, hehe. That project is listed on there somewhere as well. About half way down under: Mods & Upgrades.

Here is a link to my trials and tribulations. You can find my motor section under: Fixes/Motor Fix. I don't use this machine much anymore since I upgraded to a dedicated mill and lathe but I sure learned a lot!

 

[Packhorse]

Thanks for all the suggestions.
For the sake of getting it up and running ASAP I have brought a new motor and hope I will have it in a few days.
It cost $180NZ ( about $130 US)

I'd love a VFD. I have not researched one but Im guessing they cost a fair bit more.

 

[archer6817j]

well that wasn't very sporting!

 

[Packhorse]

You are right.
But for the price I cant really be bothered with all the diagnostics and swapping out of parts. I just need a quick solution.

Now talking about VFD's whats a good budget one to suit a 1hp single phase 240v motor?

 

[precisionworks]

whats a good budget one to suit a 1hp single phase 240v motor?

The best brand is UnObTanium

VFD's can be used only with a three phase motor. The drive takes your 1ph power & converts it to 3ph power for the motor.

Most drive conversions involve up-sizing the motor, usually double or triple, depending on how slow you want to run. A 2hp or 3hp motor (3ph) would do a nice job on your lathe.