lathe motors

the motor on my Super 7 overheats when in the high speed range , I have been given a 2 HP motor , I have read that you should not "over motor" a lathe . Whats the problem ? If you are going to get caught up in it a 3/4 HP will do as much damage as a 2 HP won't it , ? or is there some other reason Phil

No, if 3/4hp isn't enough to drive a Myford it is being asked to do too much.

2hp will do some serious damage before/ when it seizes up.

Why is the motor overheating, is the first question you should ask. Is this a common problem? I hardly use the high speed range on my Super 7, I can't see why the motor would be more susceptible to overheating though unless you have too much friction in the drive.

John is quite correct. If the motor is overheating on the high speed range, you have a serious problem within the lathe setup. There must be something that has a high drag or friction in the system. Are the belts too tight, have you got serious friction in the lathe countershaft bearings. Are the changewheels in too close a mesh or the mandrel is stiff in its bearings?

Something is causing the motor to overheat and you really must check out the complete drive chain (including the leadscrew!). The problem area should be found and rectified. Putting on a 2hp motor is no solution and is quite likely to cause some serious damage to the lathe. DON'T do it!

Andrew.

Just another thought, maybe the bearings of the motor have given up and the rotor is rubbing on the stator. This one is simple to check by just slackening off the belt and gripping the pulley. Shake it and see if you have any lateral movement. I have come across this fault, once before. The motor wasn't too noisy and I never thought that the bearings could be so worn that the rotor was rubbing on the stator!

Andrew.

I guess that the motor is getting up to speed and that it is not running on the start windings when high speed is selected >
BobH

I will check the bearings , the motor starts to smoke without any load on when on the high speed pulley , but works fine on the small drive one .

If the motor has actually smoked then it's shot! Insulation has probably been degraded, not safe to use. But replace with the right rating, even better a 0.75 HP 3 phase one with a VFD.

Oh, and even then there could be a problem with the lathe set-up.

Edited By John Haine on 24/07/2017 15:58:24

+1

John is entirely correct, I've been running a 3 phase 1HP motor with a Siemens Vector Drive VFD on my Long Bed Super 7 for over 10 years and it's great, since fitting a 32.5mm bore roller bearing head I could do with an extra 1/2 Horse or so.

- Nick

Stick to JS's advice and get a 1hp (4 pole 1450RPM) motor, it's plentiful for the work that's done on a 3-5" centre lathe.

The motor overheating sounds like it might be a problem with that particular one, but not a reason to up the power as such, if you bought a new motor a 1hp should be good enough.

I have a 3 phase with a VFD and i'm very happy with it, the speed control isn't a catch all as such, on large iron castings you still have to change the belt to a happier setting for that speed. 

I have no particular hatred of single phase motors though, I just find 3 phase lighter, safer and nicer for operations like screw cutting and tapping and reversing. 

Michael W

Edited By Michael-w on 25/07/2017 15:11:55

I've just bought in a 3 phase 1/2 HP and VFD for my ML10, and am wondering why, with the frequency range and the RPM available (5 - 1200), I need a lay-shaft at all.

Any advice on this one?