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Bridgeport back gear

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  • Bridgeport back gear

    Greets all. Hope everyone enjoyed their holiday.
    Am making this another thread since the original turned mostly into
    electrical info (thanks again!).

    Got the manual, broke the head down up to the speed selector.
    I think I found the problem with the backgear not engaging (and making
    that grinding sound) -- though I haven't taken the cam apart yet.
    Here's what I found:

    Replacement part looks to be almost $300..

    any suggestions on how to fix the one I got?

    The other side (bottom of step pulley) looks ok:

    Finally, found A LOT of old grease in here. Even in places I didn't expect it.
    Here you can see the inside of the speed selector. Hidden by the spline
    shaft is the business end of an oiler cup. So I'd expect old oil? Should there be grease in here? It's been apart before. Lots of nuts rounded over, that kind of thing. Previous owner.


  • #2
    PS.. assuming thats not a "factory chamfer" on the splined hub .. wonder
    if I just squared those back up again if there would be enough engagement.
    Or if theres a way to adjust the engagement tolerance (the cam?).

    Shy of that I'm thinking welding/grinding.



    • #3
      heres mine ..sorry about the poor pic ..ive just zoomed in on a pic i had already and cropped this portion ..

      mine does not grind

      i think its a problem with your cam shifter studs .

      i replaced mine with allen headed 8mm holes were retapped with 8mm thread,
      advantage of this mod is the shanks ofd the bolts are a little larger allowing for wear in your alloy cam slot.

      all the best.markj
      Last edited by aboard_epsilon; 12-26-2009, 02:12 PM.


      • #4
        TIG those teeth corners back up and work them backout.The cam is probably not picking the thing up far enough to clear,or isn't letting it drop down far enough to engage fully.

        The last one I had apart the cam spindle bore had some dings in it and was full of crud.Took a lite honing and some oil to let it operate smooth again.

        The cam ring,housing and cam pins can all wear.I made new pins for the one at work and made a .015" shim ring to go under the cam ring because the cam wasn't picking the jaw clutch up far enough.

        The feed worm and whatnot is supposed to have oil and not grease IIRC.See the little oil galley and drip holes machined in the worm gear cradle.
        I just need one more tool,just one!


        • #5
          That's what happens when you don't grab the chuck or tooling and give it a quick hard spin to seat the dogs.

          BrrrrrrrrrrrACK, is what you hear if you don't mate the two up by hand when you shift to low range. When some sloppy machinists did that at the shops I worked I yelled real loud, "Larry Joe's back and tearin' stuff up". They didn't like that comment at all but it did get them to quit doing damage to the mills most the time. Hell, we all forget sometimes but when you do it all the time your just sloppy and a poor machinist.

          Replace the damaged part or you'll be tearing it down again to do it right. It's easier to do it once.
          It's only ink and paper


          • #6
            300.00 or an hours welding....

            Yes if you TIG weld, you will have to get back in it later, but not for several years...

            The 4 springs that push clutch dog down were all there?

            I wish my original cam pin holes and threads were usable... I had to rotate and drill and tap new ones.

            Looks like grease might have built up in dogs too, preventing full engagement.

            Always check engagement of dogs before final assy on these things..

            My J head was a Junker and had a lot of things wrong with it..


            • #7
              I'd probably MIG weld the dogs and then re-mill them.

              No, hang on, have you got a spare mill?

              Perhaps I'd file the dogs.

              The oil cup at that level if for lubricating the quill and spindle bearings. I don't know quite where oil for those passages on top of the downfeed drive is meant to come from. The only place it could come from is from the backgear housing and I don't see that it would fall in the right place.

              I don't think the head on my BP clone had been apart before and the downfeed drive on that was lubricated with (quite clean looking) grease.
              Paul Compton


              • #8
                Mine don't look as bad as Mark's and I like his comment about the 8mm
                cam pins -- just easier that way

                I'll file the burrs off for now, give it a good clean, and hope to make some
                adjustment to the cam ala Mark's comment.

                Worse comes to worse I'll tear it down some other weekend and tig
                them back up. Tear down wasn't bad at all -- just had never done
                it before.

                degreasing was by far the worst of it. where's my project list?
                *adds hot water wash tank*



                • #9
                  While I was in the shop I checked and opps, the dogs are used for the high range side.

                  If you use what you have be sure to dress the top off as much as you can and you might want to use a little stronger springs in it. That may keep it from jumping out if the dog faces are not mating good.
                  It's only ink and paper


                  • #10
                    Oil can get to the bevel feed drive by dripping down from Pulley bearings...

                    Some works its way from backgear housing also..

                    The mill says to lube the top groove weekly, that will also drip to correct spots.


                    • #11
                      Turns out the problem isn't engaging -- but disengaging.
                      Its the cam lifter. Kudos to Mark. I can pry it up with a
                      screwdriver and turn the mill by hand.

                      Interesting bit is the cam pins won't come out. I've removed
                      the set screws, but the pins just spin in place. Even tried
                      the locking vice grips .. nothing.

                      I can see the cam pins wobble up and down as I pry.

                      It'll have to wait for the weekend -- thanks all!


                      • #12
                        There are tiny grub screws holding them

                        look at my picture you can see where they go .these have to come out first ..

                        anyway .your threads are shot now ..

                        all the best.markj


                        • #13
                          Yep the grub screws came out first.. but the pins just spin.
                          Not worried about the shot threads as I figured they'd need
                          to be recut for your 8mm bolt trick.

                          Might have to tack weld a stud on the end and jack them out.
                          We'll see if their attitude doesn't change before we resort
                          to that

                          thanks again. Tony.