VS Motor for Mini Lathe for under $125
I posted this on WOW and Woodcentral a week back, and it suddenly occured to me that I had not posted it to my friends on SMC.
Because of the character limit, I have broken it up into two postings
<b>Variable Speed Retrofit on Mini-Lathe for less than $125</b>
As most of you know, I am a dedicated Jet Mini-Lathe user (yes, I am moving up someday). You also know, that when people ask about the new Variable Speed (VS) Jet Mini-Lathe, I am quick to respond, that I was disappointed that Jet chose to put a VS motor on their lathe, but kept the same speed range (500-3975rpm). With that, the VS just became a convenience of not having to change the belt/pulley arrangement as often. You got few of, what in my opinion are the big advantages of a VS lathe – the ability to sand at low speeds, the ability to slowly ramp up the speed with an unbalanced piece, etc.
After one such rant on Woodcentral, in connection with someone’s question about retrofitting the new Jet motor onto an old lathe, received an email from a representative of the Vega Woodworking (the makers of Vega lathes and lathe duplicating machines). All his email said was “variable speed motor for mini lathe”, and the URL to their web site.
On that web site, I found that they were selling a 1hp(other sources say 2hp) VS DC motor with controller for $49 plus $8 shipping. The picture on the web site showed the motor attached to a small lathe. I called Vega, and talked to Randall McKinny, the man who had sent me the email. He told me that Vega had purchased a large quantity of these motors and controllers surplus (they are GE Treadmill duty motors) for another application, and ended up with “more than they could use in 10 years”. After some discussion, Randall offered to send me a motor, free. The only condition, if it did not work, or I did not like it, I would send it back. If I did like it, he only asked that I tell others about it on Woodcentral.
I will get to the bottom line here – I am now full time VS on my Jet Mini. However, Moma did not raise a fool, my Jet Motor and switch is safely tucked away so that I can re-install it if necessary (only takes about 20 minutes to re-install).
This motor could be attached to most any lathe (I have seen it on the internet attached to a VL-100), the process will be different for each lathe. I will describe how to do it on a Jet Mini.
This project is for the serious do-it-yourself hobbyist. It is not a plug and play operation. What you get is a bare bones motor and mount (no cover or cooling fan), a controller circuit board on an aluminum heat sink. a potentiometer (dial for speed control), and a printed wiring diagram.
The first thing that you are going to need to buy is a pulley for the motor. I found that it was hard to find a small pulley (in the .75” to 1” range) for a 5/8’ shaft. I finally just bought another Jet motor pulley. You can use the pulley off of the OEM motor, but I wanted to be able to switch back quickly if I had to. The total cost including shipping, it was less than $10. Unfortunately, the Jet Motor shaft is smaller than 5/8” (I think it is metric), so I had to drill out the hole in the pulley. I did this by mounting the pulley to my lathe chuck and drilling it using a 5/8” drill mounted in the tailstock.
Next remove the OEM motor by removing the pivot bolt in the back, and the clamping bolt in the front. The switch is a bit of a pain to remove, but not all that hard.
Remove the trapdoor on the end of the lathe that give you access to the motor pulley. You can do this by driving out the pin that goes thought the bed of the lathe and the door.
Next you will need to cut/file/grind a 1” wide, 1/8” deep notch in the top middle of the pulley door opening. I did it with an angle grinder, but it can be done with a file as well – it is cast iron, and easy to work with. You need this notch so that the motor mount will clear the bed of the lathe. For the purists out there, it would also be possible to either modify the motor mount, or construct your own mount rather than grind on the lathe bed, but I found that this was the most expedient thing for me, and if I ever went back to the old motor, the door would hide the notch.
At this point, you can slide the motor and pulley through the opening in the left end of the lathe. During my test phase, I had the lathe clamped on my workbench, and so I just clamped the motor down. In my final setup, I screwed the motor to my lathe stand.
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Let’s take a moment to talk about DC motors. This motor is rated at between 1hp and 2hp, depending on your sources (I can’t find anything about it on the GE web site). Frankly, I don’t care – it is more powerful than the OEM motor. But VS DC motors deliver less than rated HP depending on the RPM – lower RPM = Lower HP. So, if possible you want to run the motor at a higher RPM, if possible. If you are using the OEM Jet pulleys, you would want to run this motor on the smallest motor pulley, and the largest headstock pulley. Doing this will give you a speed range of 0-1430rpm. If you do spindle turning, you might want to move up to the next pulley, this will give you a 0-2500rpm range.
Now, once the motor is in place, you have to start thinking about two things: 1) Control wiring; 2) Motor and Controller cooling.
Control Wiring: A bare minimum of wiring skill is required. You need to be able to solder wire, and be able to crimp on some connectors. You need to decide where you want to place your controls. I decided that I wanted to make a control stalk, a la Oneway. You will need to buy a 110v on-off switch, and a box to contain the on-off switch and the dial for the speed control. I purchased a plastic one from electrical department at Lowes with a blank faceplate for a couple of dollars. For my original prototype, I constructed the control stalk brom ½” PVC with 90 degree long sweep elbows. That stalk worked just fine, but in the end, I made one out of copper tubing, ‘cus it looked cool. From a safety standpoint, the PVC was probably safer since I am running 100v wire through it. I have decided to put a grounding wire on the copper tubing.
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