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Thread: VS Motor for Mini Lathe for under $125

  1. #1
    Join Date
    Feb 2003
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    Phenix City, Alabama
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    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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  2. #2
    Join Date
    Feb 2003
    Location
    Phenix City, Alabama
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    Part II

    Motor and Controller Cooling: This is an important issue. Not so much the motor, because I turned for hours with this motor, touched it with my bare hand, and it would be cool to the touch, not a bit of warmth. However, the controller is another matter. There are two green voltage-reducing resistors, which get too hot to touch within 30 seconds of the power being turned on.

    The resistors are circled in green

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    There have been reports by other users, of it getting hot enough to de-solder some connections. I solved this by purchasing a 4.5” 110v fan with a filtered cover (much like a computer case fan) from Grainger (pn 3LE76, 4YD78, 4YD84). I wired the fan so that when the power was on to the motor/controller, the fan was running. Problem solved.

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    While you are working on the controller, there are several modification worth mentioning. As is, when you apply power to this controller, the motor will not start, unless you dial the speed down to zero, and then advance it to the desired speed. If while turning, you shut the power off of inspect your work, and then want to resume turning, you have to dial the speed back down to zero, and then move it back to where you were. This operation makes perfect sense, when you think about the motor/controller’s original purpose – a treadmill. However it is a pain for woodturning. The attached Rocky Mountain Woodturners URL explains how to remove one piece from the controller (transistor, diode, ???), and eliminate the need to dial the speed down to zero before turning it back up. I have done this modification, and it works great.

    Another feature of this controller, is that the speed (somewhat) slowly ramps up when you dial in a speed. Again a great feature for a treadmill, some might not want it on a lathe. I do not find it objectionable, and is somewhat of a safety feature. The Rocky Mountain Woodturners URL has a link on how to disable this feature.

    I am not going to waste your time on how I constructed the case for the controller and the motor, you can figure out what works for you. I will point out, that I placed the cooling fan is such a manor, that I blew cooling air across the hot resistors, and through the motor. The air exits out the pulley hole, and provides positive pressure to keep chips and dust out of both the motor and the controller. I also made the cover easy to remove, so that I could blow out any dust that does make it in.

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    A couple of notes on use:
    1) Any of you that already use a variable speed DC motor will be accustomed to this, but is sure is nice when I apply cutting pressure to a bowl, to have the motor automatically apply more power. There is a very slight lag before this happens, and a slight rev up when I remove pressure, but it is minor.
    2) It is very nice to be able to sand at a sub-500rpm speed.
    3) It is very hard – near impossible for me to stall the motor – the belt slips first. It is a big change from the OEM motor. I can really hog out more wood with out fear of stalling.
    4) It is nice to have the space under the lathe for tools, and especially nice when I mount my bowl steady to not have to worry about hitting the motor.

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    I want to thank Bruno Melli, at Rocky Mountain Woodturners for his information and assistance
    Article on this same subject on the Rocky Mountain Woodturners site: http://www.rmwt.org/wttips/motor.html

    A big thanks to Randall McKinney of Vega Woodworking for the opportunity to try this motor and controller. I plan to purchase a couple more, to convert my home-made grinder to variable speed, and maybe even my 1/3 hp drill press.

    http://www.vegawoodworking.com


    I would like to highly encourage you to give this a try. If you are a Mini Lathe user, it will make a huge change in your turning experience.

    Mark

  3. #3
    Join Date
    Feb 2003
    Location
    Frankfort KY
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    Keith or Aaron

    I think we've got a great article here just waiting to be saved in the "Articles Forum"!

    Mark, thanks for posting this here. I read it over on WC and was hoping you'd bring it to the Creek as printing out the keepers is really easy with this software.

    I would like to upgrade my Jet mini with this but don't know about all the electronical stuff
    Mark


    "Diplomacy is the art of saying "Nice doggie" until you can find a rock."
    Will Rogers

  4. #4
    Join Date
    Feb 2003
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    Phenix City, Alabama
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    Quote Originally Posted by Mark Hulette
    I think we've got a great article here just waiting to be saved in the "Articles Forum"!

    Mark, thanks for posting this here. I read it over on WC and was hoping you'd bring it to the Creek as printing out the keepers is really easy with this software.

    I would like to upgrade my Jet mini with this but don't know about all the electronical stuff

    Mark,

    Don't let the electrical slow you down. All you need to be able to do is solder a couple of connectors, and crimp on a couple spade connectors.
    I would be happy to help you via email or over the phone.

  5. #5
    Join Date
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    SE PA - Central Bucks County
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    Mark, is it possible to wire the controls such that the "Off" position is at the "Lo" side of the scale? I know I'd be more comfortable with it that way. (Or am I reading the dial wrong...?)
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
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    Feb 2003
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    Phenix City, Alabama
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    Jim,
    Sure. the speed dial uses about 80% of the rotation, and when you put the dial in the box, you can put the dial on so that the 0 speed is where ever you want it.

    Mark

  7. #7
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    Quote Originally Posted by Mark Kauder
    Jim,
    Sure. the speed dial uses about 80% of the rotation, and when you put the dial in the box, you can put the dial on so that the 0 speed is where ever you want it.
    Just so I am understanding you...the position you have marked as "off" is at "0" RPM and you turn the knob counterclockwise to increase the speed to "Hi". (This is the opposite direction from my OneWay speed control) I know this sounds like a stupid line of questions, but I'm thinking about picking up one of these motors to power a small buffing system for bowls and vessels and want to clearly understand what you are illustrating on your lathe installation..."the price is right"!
    --

    The most expensive tool is the one you buy "cheaply" and often...

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