Table saw pops breaker when spinning-up

[kidatari]

Howdy folks.

I purchased a Rockwell Model 10 Contractor's saw for a bargain at a road-side flea market-type sale. Other than being a bit crusty, everything is there. It's a belt-drive 120v unit.

When I start the motor with the belt disconnected, everything works fine. When I have the belt connected to the saw's arbor, the motor spins up for a second or two, and then pops the breaker.

I'm not 100% sure what to do here. I'm assuming the starting caps are OK, because the motor starts quickly and runs smoothy with no load. Any idea what to check? Thanks-

Josh

 

[NiteWolf]

try running it in a higher amp circuit. it could be that it needs that.

 

[A_Pmech]

15A or 20A circuit? Most of the "hybrid" saws require a 20A 120V circuit.

 

[kidatari]

Hmm, good point. I'll check. I tried to check the motor data plate, but it got a bunch of overspray on it at one point in time.

 

[mbatarga]

Does the arbor spin freely? If it's been sitting a while, there could be dust/grime buildup in the bearings that increase the load too high.

 

[kidatari]

Yup, that was it. (Too low amperage circuit) That saw has got some serious oomph! My first "real" tablesaw

Time to start building workbenches Thanks!

 

[dumper]

see if you can clean off the plate on the motor. Many of those saws came with 110v/220v dual voltage motors. That would help you out...if you have 220v service in your garage. Yep- that is a "real" table saw.

 

[dumper]

Yeah, what happens is with the load of the pulley and saw blade, it draws more current, explaining why it works when it is disconnected.

there should be very little load from the saw blade, belt and arbor unless there are some rusty bearings or maybe saw dust packed in somewhere- clean up the carriage that holds the blade and pulley. The belt tension is set by the weight of the motor. If you want to load test it, try ripping a 2x4. With a good blade, this saw should cut thru it like butter!

 

[jkeyser14]

there should be very little load from the saw blade, belt and arbor unless there are some rusty bearings or maybe saw dust packed in somewhere- clean up the carriage that holds the blade and pulley. The belt tension is set by the weight of the motor. If you want to load test it, try ripping a 2x4. With a good blade, this saw should cut thru it like butter!

Those motors have a huge inrush current to get started moving. My Craftsman table saw causes a pretty good voltage drop on the 20A circuit it's plugged into. A rated 3 HP nominal would be 18.6A on a 120v circuit.

 

[NJJer]

Could also be a bad capacitor on the motor, I would not assume it was good.

 

[kidatari]

If folks didn't see it earlier, I did figure out the issue.

It was caused by an under-sized circuit. I assume that this saw draws right at 15 amps. If I can get the info plate cleaned up, I'll post the details.