70's Unisaw Start stop issues

[Duane Meadows]

If the centrifugal switches has issues, it will trip the 30 amp breaker also. It just may do more damage before it does! My 3HP saw has run on a 20 amp circuit for 18 years without ever tripping the breaker. Breakers do not trip instantly and should handle the start current ok...it's only hi for a second or two.

The centrifugal switch is in the motor, under the end cover. Probably 3 screw holding the cover on(maybe only 2).

Again check the nameplate amp rating or check in the saws manual... I really don't think that saw pulls enough amperage to require a 30 amp circuit. As Rod said, it will not extend the life of the motor. Not fixing the problem will shorten it though!

[mark kosse]

Like I said, I'm no expert. I guess rockwell manufacturing wasn't either when they stamped 15.8 amps on the nameplate of my 240v only motor. Your giving bad info out.

[michael roughan]

Thanks all for the responses. I changed out the 20 amp breaker with another circuit and ran the saw from 7:30 am till 6 pm no trips, We'll see how long this lasts?

[Duane Meadows]

Like I said, I'm no expert. I guess rockwell manufacturing wasn't either when they stamped 15.8 amps on the nameplate of my 240v only motor. Your giving bad info out.

Math says otherwise... look it up, don't take my word for it!

Power = volts times Amps
15.8 X 240 = 3782 Watts.
1 HP = 746 watts.
3782/746 = 5.083 HP.

That's raw power input, not taking efficiency and power factor into account. Rockwell in those days was probably a bit more truthful about HP than many manufacturers are today. Older motor with lower effiency, maybe. But that's still likely FULL LOAD amps. How often do you hit full load on a tablesaw?

Still say it will run very well on a 20 circuit. I know mine has.

Michael, was that non stop. or start/stop for 10+ hours? If non stop, only thing that proves is it started that time... once it starts properly the centrifugal switch is out of the equation!

[michael roughan]

Duane,

I am a weekend woodworker so no the saw was not on continuously. I'd say 10-15 starts/stops yesterday and another 1o today. So far so good. If It stays like this I'll focus on the belts issue.

Math says otherwise... look it up, don't take my word for it!

Power = volts times Amps
15.8 X 240 = 3782 Watts.
1 HP = 746 watts.
3782/746 = 5.083 HP.

That's raw power input, not taking efficiency and power factor into account. Rockwell in those days was probably a bit more truthful about HP than many manufacturers are today. Older motor with lower effiency, maybe. But that's still likely FULL LOAD amps. How often do you hit full load on a tablesaw?

Still say it will run very well on a 20 circuit. I know mine has.

Michael, was that non stop. or start/stop for 10+ hours? If non stop, only thing that proves is it started that time... once it starts properly the centrifugal switch is out of the equation!

[Duane Meadows]

Michael, you could have very well had a bad breaker.. it does happen. Hope all stays well with your saw!

[michael roughan]

2 weeks and counting, almost ready to declare the culprit was an overly sensitive breaker. I swapped 2 double breakers and neither have tripped since.

Michael, you could have very well had a bad breaker.. it does happen. Hope all stays well with your saw!

[michael roughan]

Ok, one month since the initial post and the saw is behaving well. I guess changing out the breaker did the trick.

[David Eisenhauer]

I believe I have heard that the shudder is common with Unisaws and mine has done it without any issue (as far as I know) for 30+ years now. Same belts. I use a 10# extension (maybe 8' long?) for my saw that runs to a 20amp circuit without any drop out issues.

[michael roughan]

Dave,

Thanks for the feedback on the shutter. I may defer any attention to the saw until I have some free time (probably months).