Too little information to really diagnose positively, but electric
motors don't usually "wear out" slowly. When they fail, it's more in
the nature of sudden, catastrophic, and terminal.
The bearings might give out slowly, but normally you would have fairly
obvious symptoms which you have not reported, mainly noise or a rough
or gritty feel when turning the arbor by hand (unplugged! of course).
Given that the motor is likely no more than a 1½ HP (typical for a
home contractor type saw, even if it is a Sears and says more), and
even wired for 120V and even run on a 15A circuit, it isn't likely to
be tripping breakers with normal operation unless something else is
going on (like additional load on the circuit--dust collection--or
bogging down on cuts a lot, etc.). But again, not enough information.
My first suspicion would be dust, especially after 20 years of use.
I'd check the on/off switch, the centrifugal switch, even the
capacitor. Blow it out thoroughly with compressed air and see how it
Although the breaker might be the problem, and it's worth replacing
for relatively few dollars, if you want to try it, they don't usually
lose their effectiveness with just a few dozen trips--hundreds, maybe.
What's your realistic trip count?
Here's a tip from troubleshooting 101: have you added anything to the
circuit that didn't used to be there, like a dust collector? It's easy
to forget conditions that have changed since the last known
trouble-free period. In any event, what else is on the circuit?
As easy as that motor is to dismount from the saw, try taking it to a
motor shop and get a diagnosis from them. Might cost you $30 or so,
but you'll have a far more definitive answer than you'll get here.
Take the motor outdoors. Spray the berrings with trichlor, or some
other solvent. Brake cleaner is OK.
Let it dry a few minutes, oil the berrings with zoom spout turbine
oil. Two cycle mixing oil is OK if you can't find zoom spout. But the
little bottles make life a lot easier.
Let the flammable solvent dry out completely. reassemble, should work
Christopher A. Young
You can't shout down a troll.
turn off the suspicious breaker.
plug saw into a different working circuit.
does its breaker behave?
is cord or plug overheating in use?
is cord brittle or in need of replacement for any reason?
examine suspicious outlet.
are plug prongs loose or held firmly as new?
after replacing suspicious outlet receptacle,
plug a 1500 watt electric heater into the suspicious circuit and reset
it, and try the heater.
if circuit behaves, try saw.
if saw or heater trips only the suspicious breaker, replace breaker.
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