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  1. #1
    Anyone here converted a manual Bridgeport mill to CNC?

    After building my plasma table and my mini-mill, both of which are working lovely, I WANT MORE CNC ;) ;)

    My old 9x48 Bridgeport is looking for some love but is it worth it?

    It would need a ball-screw conversion kit, these are available, plus I am guessing servo drives on X, Y and Z so I have encoder display, the knee doesn't seem to get driven on the few vids i have watched so far.

    On the plus side, it's already powered via a VFD :D and i could likely recoup some cash by selling the working power feeds, control box and new DRO i fitted last year.

    Worth a look or too expensive/not good enough...

  2. #2
    Yes, done it to something similar.


    has cost me around £3000 in total by now but only using steppers plus the cost of the machine. £1500 for the ballscrews as I went full hog with high preload and C3 accuracy. Also went with £300 worth of angular contact bearings to suit. Would have gone servo's if funds had allowed then.

    Do not sell the DRO, I find it invaluable as you want to be able to switch between cnc and manual and also helps calibrate steps per unit.

    From what I read the kit ballscrews are not as good as you are made to think, hence I went with my own ballscrews.
    Machine tools and 3D printing supplies. Expanding constantly.

  3. #3
    Don't bother.
    Sell the manual and buy a dead CNC.

    You have a machine that's currently worth about £900 ? you throw close to 2K at it and have a machine worth £800
    Look for a BOSS 1 to 4 or an MDI machine. These were made as CNC, ballscrews, pressure oiling, a really nice quill where the ball screw is actually around the quill and not an add on that just wants to lever the quill sideways.

    Downside of these machine which is in your favour is the electrics were crap, sorry make that $hit. Result is the iron is very good as ost have stood the last 15 years acting a shelf somewhere.

    Beaver V5 here sold for £650


    TOS CNC mill sold for £460 OK not working but that doesn't matter for a refit.


    You could have got 1/2 of that back reselling the controller.
    John S -

  4. #4
    I think you might be right there John, it's being in the right place at the right time to catch the machines when they pop up, plus getting some transport arranged.

    Will keep looking.

  5. #5
    Am I right in my belief that if i want real-time display of position in Mach3, I need to use servo's and encoders?

  6. #6
    Quote Originally Posted by Davek0974 View Post
    Am I right in my belief that if i want real-time display of position in Mach3, I need to use servo's and encoders?
    No, you can use optical encoders too. There is a screen out there that allows you to have 2 DRO's. However, you cannot use these as positional feedback in Mach3
    Machine tools and 3D printing supplies. Expanding constantly.

  7. #7
    Hmm, just had a thought...

    Instead of dropping around £2k on building a mini-mill/router, what I should have done is use that cash to convert the Bridgeport and fit an adaptor mount that enables me to hold the 24k water-cooled spindle - best of both worlds??

    I could even mount a complete Z-axis on the rear of the ram where the slotting head should fit!

    The BP has a lovely 48" bed, ok maybe it only has 9" of Y axis but thats still not too shabby I think, certainly I've done a hell of a lot of big jobs on the old girl.

    So, what would the drawbacks be here?

    The new spindle has the speed I need, I think a BP conversion can reach 4-5000 mm/min rapids which is where the mini-mill is set so thats no issue, ballscrews would provide the same accuracy as the mini-mill has presumably.

    Last edited by Davek0974; 12-05-2016 at 02:27 PM.

  8. #8
    You lose Z travel when you convert the bridgeport's quill and another bit more when you add the adapter to hold the high speed spindle. Apart from that, I cannot see any issues except the speed at which your motors are able to move the bed. Good lubrication is key here. 4-5000 is way to quick for stepper conversions but possible with good servos. I have restriced mine to 3000mm/min actually.
    Last edited by komatias; 12-05-2016 at 02:34 PM.
    Machine tools and 3D printing supplies. Expanding constantly.

  9. #9
    Ok, but by building a custom Z-axis and mounting it on the rear of the ram I would retain whatever travel I build into the new axis, it means swivelling the ram round to change from heavy to light milling but thats about it, plus would need two z-axis drives - heavy and light.

    The Z on the heavy side is a pain, a couple that i have seen today - one replaced the quill lever with a toothed pulley and drove that via a planetary gearbox reduction - seemed ok, another replaced the fine-feed hand wheel and drove that, the ones that mount to the front of the quill I am not too impressed with, have read a few tales of quills being trashed by the single bolt pulling out.

    As for speed, so far most of my mini-mill work ranges from 600mm/min to 150mm/min - hardly blistering, I'm sure the old girl can match that ;)

    I think this may be an interesting project.

  10. #10
    Yes, that would do it. I have gone with direct drive on the quill and do not over drive it. The fine feed goes through a clutch while the backlash on the lever is too much for CNC.
    Machine tools and 3D printing supplies. Expanding constantly.

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