View Full Version : Mill/Drill Motor Questions?

12-05-2010, 02:09 PM
I have a Chinese made, round column, gear head mill drill (similar in design to the Enco 307-3387, Grizzly G1126, and Harbor Freight Zay-7032G)
The Chinese motor (which they claim is 1.5hp, 1740rpm, 1phase) is giving us problems (overheating), and so we’ve decided to replace it. The motor is mounted in a vertical position on the top of the gearbox.
My questions to all of you who own or have experience with such machines:

--Is the motor on a standard “C face” mount that I can replace with C face motors made in the US?

Will the gears and gear change system take the strain if I replace the 1740rpm motor with a 3440rpm motor? We don’t use the lower speeds on the exiting motor and the fastest speed (1500rpm) is too slow to run carbide tooling. We’ve rejected going to a 3phase motor with electronic speed control because of the loss of torque when slowing it.

Many thanks for any insights and info.


12-05-2010, 03:42 PM
You might be headed for more problems increasing the RPM because those machines are so light. Have you consided a DC motor and speed control, that seems like a better option since you require more torque.

A "C" face motor is the same any where.

The Artful Bodger
12-05-2010, 03:51 PM
A higher speed motor of the same horse power will have much less torque and presumably therefore much less strain on gears and such. The noise might increase a lot though!:)

I doubt the higher speed would be any concern to bearings etc unless you have some bushes in there.

Just my feelings on the matter.

BTW, I have a couple of Chinese motors on machines in my shop and they both feel to be running hot but they seem to be surviving.


12-05-2010, 08:00 PM
The rpms you are mentioning don't seem out of line to me. I think you'll be fine with the higher speed motor. There will be a drop in torque of course, as already mentioned.

You can always use a VFD on the higher speed motor for fine control. I think sometimes being able to smoothly alter the speed over even a small range does make an improvement by allowing you to avoid particular 'noisy' rpms.

I don't know your particular machine, but from my experience with my lathe, I seldom need the full torque that would be available when using 'back gear'. If you're in the same boat with the mill, the only problems I can forsee is gear noise and possible lube breakdown, ie foaming, etc. I doubt that would happen at the speeds you're talking about, but you might want to check it out somehow before committing to the faster motor.