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  1. #1
    Old single phase motor isnt sounding too great and likes blowing the garage fuse.
    Im convinced by the merits of the 3 phase conversion that lots of people have done.
    Newton Tesla do a 1HP kit for the myford at 470

    However ive a few questions for people who have done a similar conversion or are "in the know".
    Im happy to do any wiring so dont necessarily need "pre wired" kit, therefore is there a cheaper way to get same result?
    Im hoping to have RPM cnc controlled, will the newton tesla kit allow this?
    If not what kit/inverter should i be looking at?
    Ive been on and based on their prices the Newton Tesla setup seems a litte steep, but i dont mind paying a premium for the convience if it will do what i want at a later date, i.e CNC controlllable spindle speed.
    Ive tried to speek with Newton Tesla but the tech guys are real busy and i havent been able to get one on the phone.
    I know the Myfords have a B56 mount but what is closest alternative, there is very little in that old mounting available and other motors are much cheaper.

    Also has anyone converted there myford with Ballscrews? I havent been able to find any guides.

    I have searched but may have missed, if this is answered somewhere else please shoot me a link.
    Thanks Joe

  2. #2
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 3-4 years. Has a total post count of 591. Received thanks 79 times, giving thanks to others 5 times.
    You could probably pick up a 3-phase motor from somewhere that would do the job. My Myford is pretty flexible when it comes to motor mounting but it would be worth checking yours as they might have changed the motor mounting plate. Although seems a bit unlikely - Myford? Change?

    If you download the manual for the Mitsubishi inverter that Tesla seem to provide, it does say that it can use an external 0-10V input for speed control so it should work fine in a CNC setup with a suitable breakout board or similar. After that, it's down to how much you want to put the control box together yourself with emergency stop, fwd/rev switches, speed control pot, etc. Price doesn't seem too bad for a reasonably put-together "bolt on, plug in, go" setup but I'm sure you could do it for less sourcing parts individually.

  3. #3
    I use myself, most inverters will allow external 0-10v control and as Neale said with the right interface board your away. I suppose it should be easier to install using the kit but I don't know what's involved with the Myford.
    Last edited by EddyCurrent; 19-12-2014 at 04:34 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  4. #4
    I fitted a standard 3 phase, foot mount, TEE branded motor to my Super 7 about 10 years ago, I had to file/cut the mount holes in the plate and use thick washers on the nuts but it's held up for those 10 years (and so has the second hand Siemens drive that runs it), it will take 4mm OD reductions on 2" stainless with (using indexed carbide tooling) little curly blue chips flying everywhere, all for 165 ;-)
    I'm using a Siemens Inverter Drive but on other machines I have ABB and Mitsibushi, any of the big industrial names should give good performance, documentation and life.
    All my drives either have a potentiometer built in or have front panel buttons to give speed, jog and direction control, these can alternatively be set to external controls.
    If you buy a decent drive and read the documentation the programming isn't Rocket Science, if you buy a drive with a Chinglish manual you might struggle,
    Last edited by magicniner; 19-12-2014 at 11:28 PM.

  5. #5
    Went for this package from transwave on ebay. It's about the same price as the newton tesla kit but it has a "better inverter" in the sense that it can be cnc controlled whereas the standard package from newton tesla didn't have this ability.
    Lets hope it arrives over christmas whilst i have time off to play..

  6. #6
    Main thing to check would be the shaft size on the existing motor and make sure the new one has the same diameter to fit the pulley.

  7. #7
    The new ones a 5/8" shaft, so should be a direct swap. Saying that i didn't actually check the one that's currently fitted.
    Ill have a look in the morning...

  8. #8

    Hi Joe, I've converted my Super 7 to CNC with a ballscrew on the cross slide so far. These two pics show the fitting. I made a new bracket to fit on the end of the Xslide as I wanted to be able to convert the lathe back, so not start hacking any Myford bits. I think the PXF S7 is easier because the normal feedscrew is larger than the standard ML7 or non-PXF S7, so there is quite a large "tunnel" through the slide body which will pass a 12mm x 5mm pitch ballscrew (from Arc). In order to mount the nut I milled up an ali block which you can see at the back of the nut - this is first screwed onto the saddle using the normal feednut mounting holes, then the flange of the ballnut is bolted to it. This was an interesting job for my little CNC mill. What you can't see is that on the back of the block is a spigot to locate it in the feedscrew tunnel. As I'm using a 12 mm screw I think I can get away without a support bearing on the other end. At the drive end the screw is turned down to 8mm, it's direct driven from the motor through an Oldham coupling, and runs in a needle roller bearing in the end plate with a couple of roller thrust bearings either side of the plate.

    I'm using the standard leadscrew at the moment, with the stepper bolted to a 6mm ali plate in turn bolted on another 12 mm plate that picks up the row of machined holes along the back of the bed. There are slots to allow for belt tensioning. The stepper drives the leadscrew through a 1:2 toothed belt. It's crude but effective! I generally followed Tony Jeffree's conversion on the leadscrew but didn't bother with boring out the hole in the bearing, just fitted roller thrust races which self-align quite happily.

    There was a chap exhibiting at the Midlands exhibition who had a very nice conversion of a non-PXF S7, and I believe he is planning to make a kit available. You can see it on YouTube at cncyourmyford, and his email is cncyourmyford [at] He does a proper job on the cross slide with bearings at both ends of the screw but has to use an 8mm ballscrew since the non-PXF slide has a smaller hole through it. He also fits a ballscrew in place of the leadscrew, by dropping off the Apron and fitting a new one from an alloy casting. I am thinking of doing something similar but fabricating a new apron.
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  9. #9
    thanks for sharing this JohnHaine; very much enjoyed reading it.

    Jconway651 I have nothing much useful to add; other than keep the thread posted with whatever you decide.

    F*ck it, Im way out my depth here but I have seen one of these cheap huanyang vfd's used to power a 3 phase motor.. You would have to read up on whether its a suitable application for you but may save you some money. Im not sure if it would be any use.... I think there are some ways of controlling the speed via mach aswell.

    <span class="username">

  10. #10
    John Haine: Those are some useful pics, my setup will be similar im hoping.
    Im assuming you were talking about ArcEurotrade? Is that where you got the ballscrews? They dont have them in there catalogue or online anymore it seems.
    The leadscrew on my myford was bent when i got it so i will be going to ballscrews on both axis straight away.
    Ive seen the cncyourmyford youtube videos and was quite impressed, although im assuming for his screw cutting he has spindle driven by stepper motor, like in Tony Jeffree's where he has an electronic division master.

    Kingcreaky: Im sure this is similar to the inverter ive ordered, and im not to pannicked about the initial wiring and getting it running. However im sure the process of controlling spindle speed through mach will confuse me plenty.

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