My 13 x 40 Jet lathe motor gave up the goast. Turn it on and it
hums. It is against the wall so it is hard to see the motor but I
see capacitor gue coming out of it.
it is a 2 HP 220 VAC Capacitor start induction motor. Anyone know if
it is 1700 RPM or 3200 RPM motor?
If you can see capacitor goo then there's a good chance that all that
has happened is that you lost a capacitor, and a very slightly remoter
chance that you lost a centrifugal switch or some such and that took the
capacitor with it in time.
So why not just fix the motor?
I am going to rebuild it but I don't know what cap to buy. Plan is to
call the local motor rebuilder and ask for a cap for 2HP XX rpm motor.
I am betting the cap is dependent on the motor speed. I have to pull
the lath back from the wall to get to the motor and that is going to
be a chore. I would like to have the cap in my hand when I tackle the
job. It is a chinese motor.
All caps eventually fail due to insulation failure. If you check the ratings on
available caps, it is amazingly low. Thirty years
is excellent life. The cap is only in the circuit for a short time and actual
size is not very critical. If it looks like it fits,
What motor was on your 10 X 24?
I know chinese motors are often junk but this one has been in survice
for almost 30 years. A good part of that in production so it gets
Single phase. I don't think three phase motors need a capacitor to
This post has gotten out of hand, I was hopping for a quick answer so
I could buy one on the way home from work and be all set to fix it
this weekend. I see that isn't going to happen. I want to get it
going I feel vunrable without my lathe.
This same question gets asked and generally answered on a regular basis, and
the archives can be searched thru a Goog Group search.
The Start capacitor in a capacitor start split-phase motor needs to be rated
for AC, and the value of the cap should be in the range of 500uF per HP, or
likely 500-750uF for a 2 HP size motor.
Additionally, the appropriate cap will be rated for 120VAC or higher volts
What you saw leaking may or may not be the capacitor electrolyte, but since
you haven't disassembled the motor, it's mostly speculation. There could be
a sheet of insulating material glued to the inside of the cap cover.
Only Eyes On will determine what it is.
As you won't know anything about the condition of the motor if you only
replace the Start cap, you should be prepared to disassemble the motor,
especially after 30 years of use.
You should examine the mechanical parts of the centrifugal switch mechanism
for wear or any other problems, and repair the parts if necessary.
The centrifugal switch contacts should be closely examined, and smoothed by
burnishing them, which is a better practice than filing or sanding them,
which leaves sharp ridges in their surfaces which tend to melt.
Bearings are cheap if the motor is ball bearing equipped (most likely).
An internal cleaning can remove some dirt from even a TEFC totally enclosed
fan closed motor. There may be loose paint, rust or other debris inside the
case, and significantly more dirt if the case is vented.
An ohm meter doesn't give any useful information about the condition of a
motor capacitor, unless the cap is shorted.
To confirm that an open Start cap is preventing the motor from starting, the
capacitor can be bypassed, with a safe, properly insulated connection (for
the dimmer ones that may read this, that means: Not a screwdriver or other
hazardous method), with the load removed from the motor.
Remove a drive belt or gear to separate the motor shaft from the machine.
A bypassed cap will allow the motor to start without a load, if the cap is
A capacitor start split-phase motor will start and run normally with the
Start cap bypassed, and without the usual load applied to the motor.
The purpose of the Start cap in these motors is to increase the starting
torque rating of the motor to meet the application.
With the load removed, an good motor in otherwise undamaged condition will
start and run normally.
Other internal problems mentioned may prevent the motor from starting, which
is why one should be prepared to remove and disassemble the motor for
inspection when any problems arise.
Indeed. I was way tired when I read your original post..and it didnt
click. I came in from Los Angeles at 3:30 am..and was a walking doofus
most of the day.
If the motor has done you good service..simply change out the bad cap
with something similar. Some hardware stores stock em.
I recently had the same failure on a grizzly 1236.
the caps were marked but I couldn't get the same size cap at Grainger.
I needed the lathe up quick so I wired new caps (replace both while
you're at it) in and made a new cover.
These are pretty standard values and ratings and the HVAC industry
uses them all.
Simon Shabtai Evan
I pulled the lathe from the wall and looked at the capacitor. It was
bulging and leaking diametric all over everything. The failed
capacitor is factory supplied 110 VAC 600 microfarad beast. See
Granger for a selection of motor run caps. Note the motor runs on
220VAC. It is common for start capacitor to be rated at half working
voltage. This makes sense because the cap is sharing the voltage
with the starting coil so it only experiences =BD the run voltage.
I really needed the lathe for a job so I took a chance and replaced
the capacitor without checking the centrifugal cut out switch
contacts. I tested the motor and it appeared to work so I put
everything back together and started the job. Fifteen minutes into
it BOOM and the starter windings are shorted to ground. It was kind
of exiting because hitting the kill switch had no effect. Thank God
for circuited breakers. This time I pulled the motor and look at
the contacts and they are toast. I am now in the market for a new
motor and spent $700 having another shop make the part.
e quoted text -
Dead short to case. 0.2 ohms.
I talked to the local motor rebuilder and at $75 hour he said it just
isn't worth it. New one cost $250 to $300.
Interesting thing. 22 mm metric shaft come out to 0.870. Now if I
had a lathe that worked I could bore out the pulley 5 mill and use a
n 7/8 shaft US motor.