Inaccurate RPM speed

[Ang_Panday]

My bridgeport clone has 2hp. 3phase motor, 1,720rpm . I would like to know if it is possible that the rpm is not running as the way it should be. I use to machine 304 stainless steel at a certain SFM before, but know I can't cut it as the way I use to The SFM is 50% slower now. If I run it faster the endmill will break

Is it possible that the motor is running at a slower speed now [Confused] The motor sounds fine, but I do not know if it running right. Is it possible guy

[dgoddard]

I use a tach to check the spindle speeds against the pulley ratios. That way no doubt if the spindle matches the specs. Shouldn't be much difference but you'll probably find some. I found a tach on EBay for $30 and it's paid for itself in setting accurate speeds on both my variable speed mill and lathe.