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fraker
06-07-2013, 04:11 AM
Hi all.

As some of you may recall from my (few) earlier posts, I have a 7X12 mini lathe with the factory fitted 250W DC brush motor.

Now I have my 3 phase inverter box built and running I have been toying with the idea of maybe fitting a three phase motor and doing away with the factory fit motor and circuitry before it goes bang! on me.

My investigations suggest a 0.33 HP / 0.24KW motor would be sufficient.

My question would, therefore be; does the collective knowledge think this will be a sufficiently sized motor or, should I be looking at something a little larger.

It's perhaps worth noting that I don't take particularly heavy cuts and rarely cut anything tougher than ordinary mild steel

Your thoughts and comments are welcomed.

Thank you.

flylo
06-07-2013, 06:10 AM
Does it work OK now? Beacuse at least here puting a 3Ph on would kill the resale. As I mentioned I've used 3/4 HP motors with VS & reverse made for ConSew sewing machines with good luck. Variable speed DC motors that are 115 or 230V AC for about $100 each. They also have a brake. I get them on Ebay.

saltmine
06-07-2013, 10:28 AM
From experience, I've found that the 7 X 12 lathe has a fairly specialized motor. Speaking with the people at LMS I found out that adapting a more powerful motor might be a challenge. Especially since the motor adjusters and retaining holes are drilled and tapped into the motor case. The biggest problem I see is a limited amount of space for the motor. When it was designed, they placed the motor below and behind the spindle, to drive a jackshaft. This allows for an initial gear reduction and the ability to drive the lead screw.
Lusting for more power is what got me started on a similar quest when I heard that LMS was marketing a 7 X 12 lathe with a 500 watt brushless motor and variable speed controls.
I looked up their catalog and found the replacement 500 watt motor, but realized that the control circuit board was for a DC brushed motor, and couldn't drive a brushless motor. So, a little more shopping and I found the controller for the motor. The motor, by itself, is $249. and the controller is $214. This is not counting the numerous changes required to convert the lathe over to actually use the motor, since the brushless motor doesn't use any gears, just a belt to drive the spindle. The people at LMS suggested it might be cheaper and less of a hassle jut to buy the high-torque lathe and save myself the headache and hassle of piecing together my own. I'm afraid I'll have to agree with them. The 7 X 12 lathe wasn't designed to accept a replacement motor easily....But, that has never stopped the average HSM'er. On a good note, there is a 350 watt motor that is supposed to be a "drop in" replacement for the 250 watt motor, but they do recommend replacing the motor controller with the higher current board available. I've often thought about going this route. But, the thing that slows my progress is the $197 price tag for the motor. It's true, there are hundreds of small motors out there, some will probably work just fine, some won't. It all goes down to the way the motor is wound and what it was originally designed to do. Like Flylo said, Does it work now? If it does, leave it alone. There's a limit to how much power the machine can actually handle. A 500 watt motor is actually almost 3/4 horsepower, and as an added benefit, it was designed to use on this machine.