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  1. #1
    Silver Member
    Join Date
    Nov 2005

    Where to really start on conversion?


    New to the forum, first post. I have a J head 1968 Bridgeport that's in great shape. I want to pursue converting it to a cnc hobby, (maybe more than a hobby), machine, as this is its main purpose so far.

    I am looking for books that will layout what the differences are in CNC system configurations for the mill. Such as, the difference between stepper and servo drives, power supply requirements, control systems, ect. I obviously need to start at the beginners level. I need to learn quite a bit before I start throwing money at my mill, to reduce costly mistakes. So any recommendations for reading material, i.e., books, web pages, ect. That starts simple and help sort the overwhelming information overload that I am experiencing and helps me focus on my goal would be appreciated.

    Of course I consider this forum to be home base and the best source for my intellectual gain and practical needs throughout my transformation from manual to automated control.

    I am also looking forward to meeting the gurus and not so gurus on the forum.

    By chance, if anyone lived close enough to where I reside, my home is in Valley Springs, CA in the beautiful, (spring time), Sierra Foothills. I would consider it a great opportunity to meet and exchange help and information with anyone inclined to do so.

    Paul Austin

  2. #2
    Silver Member
    Join Date
    Nov 2005
    No help, hmmm? What's up fellas? Cat got your tounge? My feelings are starting to feel hurt because no one can even recommend a simple book for an FNG.

    Come on guys---


  3. #3
    Gold Member
    Join Date
    Jun 2005
    Where to really start on conversion?

    I would think the install of ball screws & nuts for the X & Y axis would be the first place, then the mounting of the X & Y motors. Last would be the z axis, as it can be used manually at first!

    Want to do mine next?
    Just a thought!

  4. #4
    Join Date
    Mar 2004
    We picked up a series 1 with a BOSS 8 control for $1300 on eBay in non-working condition.

    The servos worked fine, the mill powered up and we could get the axes to move, but the LCD was broken, no tape reader, etc, etc.

    We hooked up Geckos to the servos, and running EMC it works good. Total cost was probably $3k when you consider it cost $800 to rent a truck to drive from Boston to Rochester NY to get it + gas. And we spend money on Geckos, a new lube thingie from Enco, lots of rags for cleaning, few hundred running 3-phase from the panel to the mill, paint to paint the chip guard, and $400 for a PC with LCD screen from Dell to run the beast.

    Honestly, it was all setup from Bridgeport to do CNC. We avoided the whole hassle of mounting ball screws, making screw and nut mounts, mounting servos or steppers, handling backlash, running cables and wires and all of that.

    Unless it was a labor of love, I would personally find a broken CNC bridgeport and upgrade it (preferably one with seros) or buy one of those complete CNC retrofit kits.

  5. #5
    Join Date
    Oct 2004
    I have converted a series 1 J Head to CNC and am now in the process of Retro fitting a series 1 BOSS. The BOSS is the way to go, much easier as all ball screws etc are already present and its just a matter of updating the controllers and motors(if you wish) As you already have a J Head it will probably be the way you wish to go even although its the hardest. I would recommend doing it yourself rather than buying a kit as it will be cheaper by a long way and because you built it you will be able to troubleshoot should anything go wrong in the future.
    If you have any specific questions please ask, not promising I can help but will do my best.

  6. #6
    Gold Member
    Join Date
    Dec 2004
    See my conversion blog at:


    That should get you a fair piece of the way down the road. I've tried to be open about my screw ups too.

    Tip - CNC X&Y first. Then you can use that to make the Z drive. The Z-Drive is the most challenging <IMHO>

    Tip #2 - Get realistic about tolerances. As you know if you lean to hard on your Bridgy, at the extreme, the table moves at least .010". I thought .0001 was something I cared about two years ago. I'm not sure I care about .002 now. .005 is great for a ton of stuff but will waste a bearing journal.

    Also resist the urge to over build.

    I have some ideas on a better way to do the Z-Drive if you are interested I will elaborate. Essentially I think you can get a smaller screw (5/8 in.) and mount it inside the bores for the depth stop. There are some problems with this I haven't worked out, but I think there is a silver bullet here if the design can be worked on.

    I am in Huntington Beach, north OC. Are we close to each other at all? I don't have much time, but maybe........

    Later Dude! :-)


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