Great question, because I have a belt-change lathe as well. I'm pretty sure the answer is going to be "no, it will damage the motor", but I'll be watching and waiting for the experts to respond.

 

I'm familiar with speed control on motors (part of my actual job). It's easy to control the speed of a DC motor (just change the voltage), much harder to control the speed of an AC motor (change the frequency of the signal). AC drives for higher power operation (2-3 HP and above, 240V/600V) are usually very expensive.

That being said, this is probably a TRIAC switch, which is made to work with fans/blowers. I wouldn't try to use this for anything above 1 to 1.5 HP on 120V, but it should work if your lathe uses a standard AC motor.

 

Zindel, did you read the description on the motor types? Up to 15 amp, for instant start (zero to max RPM in the blink of an eye). It would probably work, but at low RPM you're gonna lose power. You might make it up on using the slower setting on the pulley…..... I'm not an electrical expert, but I tried that once on a DC motor. I had execellent speed control, but at slow speed, the loss of power was really bad. I could stop the rotation with the slightest cut. At full 3200 rpm, I had full power, but that's too fast for me, and it took a lot of slow speed turning before I was ready for the full speed.
I changed out to 3 phase and VFD…........ Jerry (in Tucson)

 

Junado thank you! sounds like i should be fine as i think it is only a 1/2 hp motor anyways. Nubsnstubs i agree i would expect loss of power but i would think the only thing i really want to crank the speed down too much is just for doing sanding and applying finishes. Again i don't do turning so i will probably find the right speed for what i use it for using the pulleys and just turn it down to sand and finish. that way i have only two speeds…my max speed which i turn at and my slower speeds for finishing. then again i may come to find that this isn't the perfect configuration but then i can always go back to moving pulleys.

 

It will rob power at very low speed, but the power to speed ratio of an AC motor is very different from a DC motor.

While a DC motor's power is directly related to its speed (0 RPM = 0 power; max rpm = max power), an AC motor works differently. See http://4.bp.blogspot.com/-13OcG8RGPvM/UhdN_f220FI/AAAAAAAACB0/xSUaRPCiz64/s640/Ac-Motor-Power-Curve2.jpg (these are curves for various AC motors, but the general shape of these curves is what I'm trying to show). As you start putting resistance on an AC motor, it's power output increases as its speed decreases. AC motors at stall are a lot more powerful than DC motors.

This is a switch that acts like a very cheap VFD (Variable Frequency Drive, tends to be expensive, but are much more reliable), but using cheaper electronic components (transistors).

 

Router speed controlers are for a universal motor (with brushes), not an induction motor (no brushes).
Having said that, my standard disclaimer is now in effect.
Disclaimer:
I have been wrong before.
Bill

 

I hadn't thought of the distinction between universal and induction motors. Bill is probably right since this is marketed as a "power tool" speed controller. However, this could still work on a single phase induction motor: TRIAC switches, like those used for controlling ceiling fans and such, will work for single phase induction motor, but rely on letting the motor "slip" through its rotation by reducing the voltage. This is not the "proper" way to control an induction motor, but it usually works. Robs a lot more power than a proper VFD.

The best way would be to use a variable frequency drive, but those are a lot more expensive (100$+).

 

It is my understanding that adding resistance will not rob just a little power, but a LOT of power. I'd stick to the belts, easy once you get the muscle memory working.

That said- I read where a fellow took a motor and controller off a treadmill and mounted it on his lathe. For the price of a used treadmill he had true variable speed. If I tried that, my wife would have to work a little harder to keep the treadmill going without a motor, but heck, she never uses it anyway!

Or- wait- I'll then mount the lathe motor with its single speed onto the treadmill. Run, baby, run!

 

Generally a VFD won't work with a 120V single phase motor, it can be done but only with some motors. You more often see them on 240V 3 phase motors. The router speed control isn't going to work, at least in a satisfactory fashion. I would give up on your current thinking, and consider moving to a lathe with electronic speed control built in. You may find that such a lathe will still have some belt changes to do, but it's more within a range, rather than a precise speed.

 

whoops- how do I fix a double posting?

It is my understanding that adding resistance will not rob just a little power, but a LOT of power. I'd stick to the belts, easy once you get the muscle memory working.

That said- I read where a fellow took a motor and controller off a treadmill and mounted it on his lathe. For the price of a used treadmill he had true variable speed. If I tried that, my wife would have to work a little harder to keep the treadmill going without a motor, but heck, she never uses it anyway!

Or- wait- I'll then mount the lathe motor with its single speed onto the treadmill. Run, baby, run!

 

So im getting mixed reports I may just stick with belt changes as my use on the lathe will be very minimal so it shouldn't bug me a ton, i was just looking for an easy way to add a nice little feature.

 

to put it to rest, absolutely not. I have the same controller only from HF. It will work for any universal non soft start motor. I believe it will burn up the start switch in an induction motor. We really need Topomax he would know the science behind it. I am in the process of grafting a 2 1/2 hp treadmill motor to my C-man lathe. I posted an ad on CL looking for a free treadmill and all I had to do was pick it up. I had a 2.5 hp dc motor and controller. I am in process of having a friend machine the flywheel to accept the stock step pulley. this way I still have the belt adjustment but I can also dial it up and down as needed.

 

IN a word (NO) as explained it won't work with non brushed motors best way everyone else seems to be doing for speed control is going down the 3 phase route and using an invertor with forward reverse ,speed control,soft start possinbilities etc etc that's what I did chenged everything fron single to three phase and used an invertor actually I have done the exact same thing on many of my machines inc metal milling machines, lathes, etc, etc. Alistair

 

I have what sounds like a similar craftsman lathe. Mine used a 1/2hp split phase capacitor start motor and the triac type speed controls will work with this kind of motor only after it is past the start phase and into the run phase. Most of the more expensive variable speed lathes have a three phase induction motor run with a VFD requiring only single phase input with three phase output. This kind of setup is expensive for the VFD and usually pretty cheap for a used three phase motor. My solution was to get a 1hp heavy duty DC treadmill motor and drive out of a broken treadmill I got for free. The low speed torque is probably less than the 1/2 induction motor, but leaving the belt on the lowest speed helps that problem and offers enough speed adjustability to run the lathe at or near the previous top speed without having to move the belt. This setup has worked great for me so far, the motor has enough torque even at very low speed to slip the belt with the spindle locked.

 

It occurs to me that the treadmill motor approach would not give a reverse setting. Nice to sand while running backwards and forwards!

 

baby steps until you have the disposable income to drop $4000 on a lathe. Also keep in mind when you upgrade you may want to sell the old lathe, and if you have to much invested then you will lose money on the old one.