View Full Version : Simple motor questions

03-12-2015, 10:10 PM
I finally got my Clausing milling machine setup (pictures soon) and found that the motor won't start without a little push... it just makes a loud buzz. If I spin the belt a bit, it starts and runs fine.

The motor is a 3/4 HP Hoover capacitor start motor that looks like it's probably at least 40 years old.
I unscrewed the plugs at the bearings and there seems to be some old dried grease in there.

I haven't had a chance to test the capacitor (all I need to do is measure resistance and see if it changes while measuring, correct?)

What's the best way to clean/revive the grease, and what should I be using?

My inclination was to spray some brake clean in there while spinning the motor by hand, then blow it out and replace with some lightweight oil (spindle oil perhaps). Am I going to just make things worse?
I'd like to avoid disassembling it if possible.

TIA for any words of wisdom.

03-12-2015, 10:43 PM
at 40 years old-- replace the capacitor first. They are electrolytic (uses a liquid) and they definitely will dry out and not provide the rated capacitance. You could get a meter to measure the cap, but just replace it.. The grease can be cleaned off with any petro based solvent and replaced with new ----I would just oil it well first and run it a while ...grease will soften with the oil and make it easier to add new grease. If the bearings are good that's a better motor than what you get today.

03-12-2015, 10:57 PM
Thanks. I'm guessing that the capacitor will be marked in a meaningful way that'll allow me to find a suitable replacement?
Sorry for the probably obvious questions, but electric motors are a little outside of my experience.

I suppose plan B would be to fit one of the many 1/2 HP motors I have lying around my shop. I have a pretty nice original Atlas that would go well, but the extra HP might come in handy some day.

Other than the balky motor, I'm already liking the little Clausing a lot. It needs a serious cleaning, but so far, everything seems to be in good working order. The top of the spindle has a little wobble in it, but that only seems to be above the top bearing.. I haven't measured runout at the cutter end yet, but I made some test cuts in steel and aluminum and the finish was excellent.

03-12-2015, 10:59 PM
If you can push start the motor and it will then run, that suggests that the bearings are ok - you still need to do the lube thing of course. I would probably use spindle oil generously, and keep cleaning up the excess so you don't create a dust magnet. Once it appears that the grease has become 're-moisturized' you can start using a heavier oil like 3 in 1, or similar. To begin this process, I'll often use Nutrol, which is a contact cleaner. It is able to penetrate and has a light oil base, so it gives some measure of lubrication while dissolving the old grease. It's too light to be a lubricant on its own, so you must add a heavier oil as soon as you see the mysterious green compounds oozing out of the bearings.

The starting problem would most likely be the capacitor or the switch. Both need to be looked at- switch first probably, as that can often be rejuvenated at little or no cost, and being a physical thing you can see what's going on with it.

Capacitors can and do dry out, but don't discount one because of age. I've found that many new ones are just crap, and I've had motors running for decades with the original caps.

J Tiers
03-13-2015, 08:24 AM
It probably does have capacitor.... but not every single phase motor does. Don't be too surprised if it has no capacitor, in that case the internal starting switch may be bad or sticky.

03-13-2015, 09:30 AM
It probably does have capacitor.... but not every single phase motor does. Don't be too surprised if it has no capacitor, in that case the internal starting switch may be bad or sticky.

Yes ..the start switch is the next step whether internal or a "start relay" (little black box) It's almost certainly the cap or the sw. I've never run into a motor with bad stare windings yet.

03-13-2015, 09:44 AM
There's a big housing on the side, so I'm about 99% sure that there's a cap in there.

I'm guessing that accessing the starting switch is going to require taking it apart... something I was hoping to avoid if possible.
Oh well... there's probably 50 years of dirt, grease, grime and chips inside there, so it's probably the right thing to do.

Once it's started it runs great.. smooth and quiet. It's definitely worth saving.

Thanks all for your help and encouragement.

03-13-2015, 09:51 AM
The factory Hoover motor on my Clausing 8520 had a very pronounced
single phase humm and drone. If you do not realize, this phenomenon
is a characteristic of single phase motors, although some are better or
worse than others. I actually collect and safe for later use, single phase
motors that I come across that are particularly quiet. They are kind of
rare, perhaps a very good quality build or extra varnish in the windings
dip, extra bit of weld in the iron laminations, the perfect position of the
shaded pile shorting bars.... whatever the reason, there are a few quiet
single phase motors out there. They are just very hard to find.
Some of you know what I am talking about, and some have most likely
never noticed really how loud single phase motors actually are. If you
need an example, turn on and run ANY Chinese drill press. These things
always vibrate like a nervous nun in a whore house.
One very quiet single phase machine that I have, is an Atlas drill press.
It has a capacitor start, induction run motor from a house furnace.
It is a 1/6 horsepower GE motor, 1800 rpm. Bronze bearings and it is
a solid base mount (not the resilient mount that most furnace motors
have.) This drill press with this motor is so quiet, you almost can't
hear it run. It is such a pleasure to use. Put it next to a Chinese drill
press and it is like fire and water difference.
This is all good and fine, but the real solution is a 3 phase motor and
a VFD if you do not have 3 phase. Most all three phase motors run
very smooth as compared to single phase motors. Only cheap or
bad bearings typically make them loud. (easily fixed). On my 8520
mill, I replaced the noisy Hoover (ironic, loud as a vacuum cleaner)
motor with a 3 phase motor, (with VFD) and life has never been
better. What I really did was replace the entire Clausing head with
a Bridgeport M-head (#2mt). What a nice mill it now is. I also
added a DRO and it is heaven to use. I love the light feel of the
controls compared to a full size Bridgeport sized mill.
Good luck on your mill and let's see some pics.



03-14-2015, 06:21 PM
Thanks to all.

I pulled a capacitor off of an old Craftsman 1/2 HP motor and installed it on the Hoover. Didn't bother to test the old one since the contacts were a mess and had been soldered on.

Now she starts right up and runs smooth and quiet.

03-17-2015, 07:44 AM
DO NOT USE BRAKE CLEANER ON MOTORS! I learned the hard way. It eats shellac/poly off copper windings, which will short the coils. I was helping a guy repair a bandsaw flooded in hurricane ike. I needed to clean all the sediment out. I should have just rinsed with water and lubed it. Lesson learned...