Slowing my lathe

Well, clearly, if I could find a way to feed it 50 Hz it would run ok since that is the design frequency for this motor. I would think I could run it a bit below that (not heavily loaded) if I had a way to produce the input power.

Take the single phase motor off and throw it in the trash. Put on a decent 3 phase motor and use a VFD. That's what I did and never looked back. VFD + back gear = 20 rpm easy. Wonderful for threading.

50 Hz would not slow it very much; only to 5/6 of its 60Hz speed.

Bob Swinney

Cheapest route is to replace the motor. Measure your pulley diameters and calculate the motor speed from your desired spindle speed. Don't forget the back gears.

Then decide if you need a 1725 rpm motor or a 1200. I doubt you will need slower than 1200 unless the lathe is a bad design, but you could go to 800 rpm.

Get the data from the motor plate. take it to Graingers and tell them you want one that runs 50% slower. Or as another said go 3 phase and use a VFD. There are also multi speed single phase motors. Would mean some more wiring.

Bob AZ

Bob AZ

I pulled a 1 1/4 hp 90VDC motor from a treadmill that saw more use as a shelf than miles. You can get motors and controllers from

Probably cheaper than a 3phase motor and a VFD, and that is from me presuming that since you have an Asian lathe you likely can't or won't pay for the best stuff.

Good info.

You're right about not spending too much. This lathe seems in pretty good shape, has good tooling, and was upgraded with a good DRO, but it would be foolish to put a lot more money into it.

I would also advocate a DC motor for 1 HP. I think the treadmill motors run considerably faster than 1725 RPM when delivering full power, but the ones I've looked at are series-wound so they can deliver some torque at lower speeds and they're easy to speed-control.

Small VFDs are pretty cheap. Try Dealers electric. And used 3 phase motors are also pretty cheap. Get rid of the single phase motor. They have, right now, a package that includes a 1 hp totally enclosed motor and a VFD for $282.00. The thing takes 115 volts input and outputs 230 volts. Also, the have a 1 hp VFD model F101, new in box, for $161.00. And if you think that maybe this is too much money to spend on the lathe, think about how many hours you will use it. The $282.00 price isn't bad, really, and it will all bolt in. And you not only get that low speed you want, you get an infinite number of speeds between the low and the high just by turning a dial. This can be really helpful when trying to achieve a certain finish or when trying to eliminate chatter. ERS

Thanks. Did some looking around their web page. Seems like a reasonable way to go. I'm in California and they are in NJ. Wondering if there are similar vendors closer to the west coast? (Shipping less?)

Looking at the motors, I see they have descriptors like Frame: 56, 143T,

145T. Is there a good reference on the web or elsewhere to what these mean? Seems I should figure out what I need to fit the lathe.

I found a reference here...

so that's covered.

Junk the AC motor and stick on a DC one,

Go here to see how I did it....

dave

The VFD is light. Buy a used motor where you live and have the two or three pound VFD sent. Or check surplus places around your area. Mebbe they'll have the whole thing. ERS

Seems to me that the actual costs are a little higher than just the price of the VFD alone. I'm not much of a scrounger and probably approach it wrong, but a typical VFD installation for me includes a new 220 VAC breaker, about

20 feet of Liqui-tite and some fittings, a fused disconnect box, and a bit of conduit, which adds another $10 or so to the price. For the surface grinder I also added a Hoffman box as an enclosure for the Hitachi VFD to try and minimize metalic dust settling on the electronics and to contain the wires to/from the VFD, plus a relay and diode to supply logic for 3-wire control to save having to replace the grinder's existing momentary switches. At one point in the acquisition of machine tools the available breaker space in the main breaker panel was exceeded, and a new sub-panel was required.

If it ain't one thing, it's another.

Mike

So after looking a while, I seems this lathe has a metric motor (surprise).

Looks a bit like NMEA form 143T or 56, but those shafts are .875 inch. Mine is .945 or 24 mm. Seems like I want an IEC 90S form motor, but I read that not all manufacturers have standard shaft dia.

Friggin' foreigners (kidding :)).

Anybody know good places -- preferably in west US -- to look for an IEC

90S style, 3 phase, 230V motor, 1.1 - 1.5 KW (1.5 - 2 HP) with a .945 (24mm) shaft? Cheap is good.

Thanks, again for any further help.

Since you only need one, why don't you make a reducing sleeve to fit in the larger pulley bore? That's what your lathe is for. You will need to cut a slot for the key to pass thru. And you will probably need to modify a key. Because the key in your motor is metric. If it's an 8mm key you're in luck because 8mm is .3149 and 5/16 is .3125. So only a little filing will narrow the bottom half of the key. The key needs to be a snug fit in both the shaft and the pulley. Making custom stuff is what metalworking is all about. Eric

Yes, I had thought about using a sleeve in the pulley. I guess that would give me a lot more motors to choose from. The key has me a bit puzzled. Measuring its width at the end of the shaft, it seems to to be about .290 or 7.4 mm. That makes no sense to me, but this is an early Taiwan lathe, so I guess anything is possible.

It doesn't really matter what size the key is. As long as it fits snugly in the pulley. Then filing or milling the other part to fit in the motor shaft snugly. If the key is loose in the pulley go to a good hardware store and buy one that is unless you have a mill and then you can make one from scratch. And you REALLY need to consider why you bought the lathe. If it's to make money then maybe saving the time it takes to make a custom key and sleeve is a good thing. But if it's for hobby, or learning, or both, then make all the stuff you can. That's how you get good. And don't be scared. If you scrap the sleeve then make another. You can even make the sleeve out of aluminum. It's not a wear part. It will be trapped between the pulley and shaft. And it's a small motor anyway. I have a couple customers who have some machine tools. They will have me make stuff for them from time to time. I encourage them to make it themselves. Then they call up or stop by and show me how they made this or that and it really thrills them. I still get the fussy parts and they get to learn. Isn't that why you read and post here? Good Luck, Eric R Snow, E T Precision Machine