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Bridgeport Mill - Clatter when backgear (low speed) is engaged. (Series I - J-Head)

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  • Bridgeport Mill - Clatter when backgear (low speed) is engaged. (Series I - J-Head)

    Just when things were going so well. First time I tried to engage low and run, the head let out a clatter and I hit stop as fast as I could. After looking it over, I determined the Direct Drive Lever (high speed) doesn't raise the clutch far enough. I can put a large screw driver on the step pulley then raise it about 1/16"+ and move the pulley without hearing the ticking (when rotating by hand). It's the ticking that turns to clatter when the motor runs. (At least it appears so.)

    Is there any adjustment to this other than making a shim to go under the direct drive lever collar on top? I think I could use the three nuts on top to hold the shim(s) in place. When in high gear, that collar is loose anyway.

    I also noticed the lift pins (held in place by tiny set screws) seem a little loose. I'll go through that before making a shim.

    On a better note, I almost have the DRO installed.

  • #2
    Loosen the set screws for the lift pins, tighten both lift pins (should be a slot on the outside of them). If the lift pins don't fully tighten then the threads are stripped.. There should be another set of holes if you remove both lift pins and rotate the hub.

    If those pins have ANY play then they will not lift the hub high enough to clear the cogs and you'll hear a horrible grinding/clanking noise.

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    • #3
      Thanks! I'll give that a shot.

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      • #4
        Yep. I've been making chips with the mill already. Just adding a few accoutrements and tools. I set up to slice one of the DRO scale mounts to make angled shims for the Z-scale. I'm pretty sure I tested the mill in back gear but this was the first time I actually tried to use it. Isn't that always the case?

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        • #5
          I kind of have that clattering sound you seem to be talking about on my mill. Can you explain these lift pins in more detail? I'd like to understand what you're talking about so I can make the same adjustment.

          PS>> I have a variable speed head too, by the way.

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          • #6
            Those "pins" refere to the step belt version.

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            • #7
              Ah, so only applies to step pulley. Well I'm pretty sure the rattle I hear is the flat-splined mating point of the two upper and lower shafts - items 31 and 33 in this diagram:




              Is there a way to adjust this system so that these two shafts more firmly engage, and hopefully eliminate the rattle that I think is coming from them being too loosely engaged??

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              • #8
                Originally posted by Machine View Post
                Ah, so only applies to step pulley. Well I'm pretty sure the rattle I hear is the flat-splined mating point of the two upper and lower shafts - items 31 and 33 in this diagram:




                Is there a way to adjust this system so that these two shafts more firmly engage, and hopefully eliminate the rattle that I think is coming from them being too loosely engaged??
                Does the rattle go away when your in low speed mode? In low speed mode, #31 and #33 are disengaged.. The drawbar also rattles around.. Try touching the draw bar while it's running to see if that changes the rattle sound in any way... If it's the drawbar then just consider that bridgeport music to your ears.

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                • #9
                  Originally posted by Machine View Post
                  I kind of have that clattering sound you seem to be talking about on my mill. Can you explain these lift pins in more detail? I'd like to understand what you're talking about so I can make the same adjustment.

                  PS>> I have a variable speed head too, by the way.
                  When the lift pins are loose or stripped, the sound is more like a freight train crashing though a nitroglycerin factory in the head.

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                  • #10
                    Thanks for the tip. I just checked it and I found that the noise is much less rattly in low. And I notice that when I move the high/low lever (item 61 & 62 in the above diagram) to a more engaged position (beyond the detent) and the rattle in high pretty much goes away. So I need to adjust the detent to more fully engage the two splined shafts. Thanks again for the tip, nice to have my Bridgeport as quiet as possible.

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                    • #11
                      The dog engagement splines do wear. If they are rounded over, they will not engage well; "new" they are slightly tapered and fit tight. Other areas of rattle are the male spindle splines, and the female splines in 33. The varispeed system can (will) also wear and rattle. You also need to "float" the entire upper section in to align 31 and 33 - I quietened a few buy just doing that.

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                      • #12
                        31 & 33 the "clutches" are spendy items too, before I got fed up with the racket and changed mine I tried to find alternatives to the £££ clutches, came across a redneck solution where a cork is kept in constant contact with the running spindle introducing a bit of drag thus somewhat quieting the noise, sadly mine were too far gone for that even.

                        Paul

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                        • #13
                          Originally posted by lakeside53 View Post
                          The varispeed system can (will) also wear and rattle. You also need to "float" the entire upper section in to align 31 and 33 - I quietened a few buy just doing that.
                          Thanks. I bought the H&W Vari-speed rebuild kit and replaced all the bearings (including motor bearings), plastic bushings, belts, cleaned and greased the entire bullgear assy. The Varispeed system still squeaks and groans here and there, but I assume those noises are mostly "normal" Bridgeport sounds.

                          Can you explain this "floating" process? Do you mean when you assemble the upper head you loosen all the bolts securing the housing or something else(?), then fully engage the splines and then tighten everything down? I assume this aligns the splines and thereby quiets the engagement clatter?


                          Originally posted by _Paul_ View Post
                          31 & 33 the "clutches" are spendy items too, before I got fed up with the racket and changed mine I tried to find alternatives to the £££ clutches, came across a redneck solution where a cork is kept in constant contact with the running spindle introducing a bit of drag thus somewhat quieting the noise, sadly mine were too far gone for that even. Paul
                          Yeah I inspected my splines when I had the machine apart and they were a little rounded, but not too bad. I see that replacing the two together will cost close to $500. Thankfully, based on how quiet it was after a minor adjustment, I don't think I need to replace them.

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                          • #14
                            "Floating"... lightly loosen the three bolts from below, run the head about 1000rpm, tap the upper casing left/right/whatever with a large rubber hammer until it all sounds right, then tighten. It can make a huge different to the sound and aligns the dogs.
                            Last edited by lakeside53; 10-20-2017, 08:39 PM.

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                            • #15
                              New pins in the alternate holes did the trick. Thanks Adrian!

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