Bridgeport Back-Gear drive

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  • Davek0974
    Senior Member
    • Aug 2007
    • 1463

    Bridgeport Back-Gear drive

    Can anyone confirm or deny that on a Bridgeport series1 with (what used to be) a 2J head, the back-gear drive-train is running 100% of the time the spindle is regardless of the position of the back-gear lever?

    I'm fairly certain it does but wanted to confirm before i disconnected my one - I only run pretty much flat out now since CNC'in the old girl and the back-gear drive seems to be the source of most of the heat and noise in the head.

    There are no vari-discs anymore as I run 1:1 toothed belt drive and also no quill power feed stuff up there as its' CNC now.

    Thanks
    If it does'nt fit, hit it.
    https://ddmetalproducts.co.uk
    http://www.davekearley.co.uk
  • lakeside53
    Senior Member
    • Nov 2007
    • 10511

    #2
    That is correct.

    Heat? Shoudn't be any from the gears etc.

    Rattly noise is typically from the dog engagement when you are in high gear. Going to be harder to get rid of that one.

    Comment

    • Davek0974
      Senior Member
      • Aug 2007
      • 1463

      #3
      Ok thanks

      It gets pretty warm after an hour or so running at 4000rpm.

      I'll disconnect everything so all i have is the motor, belt and spindle, thats about as lean as it can go really.

      If i had space and power, a VMC would suit but there are none that have a bed the size of a 48" bridgeport and such a small footprint.

      I'll stick with the 3Hp motor and VFD for a while then look at an AC servo maybe.

      I think 5000rpm is not too far out of range, they are rated at 4200rpm from stock But not with the back-gear stuff running as well.
      If it does'nt fit, hit it.
      https://ddmetalproducts.co.uk
      http://www.davekearley.co.uk

      Comment

      • Toolguy
        Senior Member
        • Jan 2010
        • 6666

        #4
        Another big source of heat at higher RPMs can be the spindle bearings. If you clean out the bearings and put in Kluber NBU-15 bearing grease, they will run cooler. Also, a major source of noise occurs if the top of the head is misaligned with the part below. You can loosen the bolts underneath and move the top part around to find the quietest spot (with the spindle running a moderate speed), then tighten the bolts.
        Kansas City area

        Comment

        • Davek0974
          Senior Member
          • Aug 2007
          • 1463

          #5
          Thanks, i'll try floating the head in.

          These bearings run in oil, this one was built that way, oil cup on side of head. Maybe when i need new bearings i'll grease them with kluber.
          If it does'nt fit, hit it.
          https://ddmetalproducts.co.uk
          http://www.davekearley.co.uk

          Comment

          • lakeside53
            Senior Member
            • Nov 2007
            • 10511

            #6
            Originally posted by Davek0974 View Post
            Ok thanks

            It gets pretty warm after an hour or so running at 4000rpm.

            I'll disconnect everything so all i have is the motor, belt and spindle, thats about as lean as it can go really.

            If i had space and power, a VMC would suit but there are none that have a bed the size of a 48" bridgeport and such a small footprint.

            I'll stick with the 3Hp motor and VFD for a while then look at an AC servo maybe.

            I think 5000rpm is not too far out of range, they are rated at 4200rpm from stock But not with the back-gear stuff running as well.
            It's not the back gear that's the issue - it's typically the dog drive that couples it to the spindle spline drive. The back gear is just a nice balanced flywheel. The small gear it drives/driven is inconsequential and fully bathed in grease.

            I run mine to 6K often, and occasionally 8k.. (6 sae spindle oil) with all the varispeed installed. My spindle runs cool to maybe slightly warm and often runs many hour a days. YMMMV!

            Not too keen on putting grease in open bearings; it was designed as a full loss system. There is a variant for woodworking that has sealed bearings.
            Last edited by lakeside53; 04-23-2018, 10:18 PM.

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