Bridgeport clone spindle too fast

[jgedde]

Thanks for the input, guys.

I checked cal on the tach with my belt-drive drill press. According to the belt chart, it should be 540 RPM. Tach reads 510 +/- 2 RPM. About a 5% error--within expectation.

My tach has a bright red illuminator, and a red filter on the detector. This filters out most ambient light. It came wit some stick-on highly reflective strips, kind of like what highway signs have on them. To eliminate extraneous false reflections, I wrapped the spindle with black electrical tape and put the reflective pad on the tape. Readout on the head says 500, tach reads a pretty steady 960.

I also checked to make sure the dial on the head readout hadn't slipped. It hadn't--The speed adjust is turned all the way to its stop on the slow side, and the dial reads 500, just what it should.

Is it a PITA to pull the motor off? I'm guessing at this point you'll find it's running 2X as fast as it should for the reduction in your mill...

John

 

[ed_h]

John--

It's the original motor, 60 Hz, 220 VAC, 1725 RPM. Since an induction motor's speed is tied to the line frequency, I can't think of what could cause it to run fast.

I'm thinking now that the adjustment mechanism just isn't allowing the full range.