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help with split nut on BP

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  • help with split nut on BP

    I just purchased a 1958 J head step pulley BP. It was loaded with a fork lift and disassembled to unload it when I got it home with the aid of an engine hoist. So since it is in pieces, I'm looking over things and cleaning them up best as I can before re-assembly.

    the split nut had tons of chips heaped upon it (previous owner used grease - didn't help ) I wanted to remove the split nut from bracket and dig out all the old grease, but I can't remove the set screw. The lock screws came out fine, but the set screws won't budge. The head of one shows signs of being stuck before ( or still stuck ) as the machine had about .030" backlash......

    I have drinched it in WD-40 now......and letting it set.

    Any advice??
    Last edited by elginrunner; 06-16-2012, 01:09 PM.

  • #2
    Do the set screws have a socket head or a screw driver slot?

    If the former I'd try drilling them out and using an easy out. I've even used a hand drill for this application.

    You may need to set it up in a drill press and drill out the set screw using the appropriate tap drill size. Once you have it apart you could then clean up the threaded hole with a tap.

    Heat may also be helpful as bronze expands more than steel.


    • #3
      If you are going to drill them out, I'd recommend using a left hand drill bit, a lot of times with a left hand drill they'll back out part way through the drilling process.

      Paul T.


      • #4
        First check that the screw is not bent, the head of the screw can be tipped side ways and won't want to come out, clean the area of the head, look carefully the head should be parallel to the housing, if not VERY carefully using a small hammer tap or beat the head back parallel to the housing, or use a large screw driver and unscrew it, be careful the heads have been known to break in half. When I ran into that problem I would just make a new screw using an allen bolt and turning a stepped washer that the allen bolt would press into, never had one of these break, had a lot of slotted screws break.


        • #5
          I would also get some penetrating oil, like Kroil or PB Blaster. I find WD40 doesn't have the lubrication even if it does penetrate. A lot of the "uses" people recommend for WD 40 are just expedient attempts because the real stuff needed wasn't there.


          • #6
            I agree with Joe. Forget WD-40. Use PB Blaster or Kroil. The PB Blaster is sold at Wal-Mart or Tractor Supply. Also any real hardware store should have it.


            • #7
              The set screws are the slot screwdriver head, or as my daughter used to say it's a "minus".

              I'll get some PB blaster on my lunch break tonight...


              • #8
                If the geometry allows it - light tapping on the end of the driver whilst twisting will help you break it loose - they also make very affordable impact drivers for doing the job - you strike them with a hammer and some spiral internals do the rest...


                • #9
                  Kroil is the best stuff Ihave ever used! Give it a day and it seems to work every time. Don't think it is possible in this case, but every time I'm faced with a tough one, I double check to make sure it is not a LH thread. Bob.


                  • #10
                    help with split nut on BP (update with pics)

                    Well after some PB blaster and a little strain of the muscles, I got the set screws out. I'm cleaning it all up and thought that the nuts looked fine, but wanted educated opinions.....

                    and the other one...

                    And was just wondering about the keys.... looks like worn cross pins for some reason...

                    Last edited by elginrunner; 06-16-2012, 01:15 PM. Reason: update title


                    • #11
                      So long as it can be adjusted to take out the slop, it will work fine. Real question is... how is your lead screw? Just caliper the top width of the acme at the ends and the middle. That will give you a rough indicator of the wear and let you know how sloppy the middle will need to be to allow travel to the ends.


                      • #12
                        So I've measured my lead screw. The top of the acme threads measure .0880 on the ends of the shaft and are a consistant .0775 in the middle. At what point does the screw need to be replaced?


                        • #13

                          Firstly Ive had good Sucess using a Motorcycle Hand held impact tool. Insert the correct tip (or regrind one to suit) and hit with hammer and screws loose. Secondly i have fissled with my step head 1941 Bridgeport leadscrews and nuts and have found a cheap easy repair. I remove the Nut and stick it in the Lathe,,i cut the nut in Half and reinstall it... Then with the screw on the end of the nut bracket just snug it up until you have the lash backlash you desire NOW if youre screws screwed you will notice during the machine tables travel it tightening up ,,,just back of scre a bit more to loosen up the nuts . I did this years ago and eventually bought a new screw and nut. I also religiosly oil my machine and i dont use grease on the thing. Hope this helps you Mike


                          • #14
                            Originally posted by elginrunner
                            So I've measured my lead screw. The top of the acme threads measure .0880 on the ends of the shaft and are a consistant .0775 in the middle. At what point does the screw need to be replaced?

                            When to replace? Much worse than that.


                            • #15
                              .011 " wear is not that bad.
                              It means if you tighten the nuts until the table is hard to move when at extreme locations you mayl have about .011 " backlash in the middle.
                              Some folks figure that is too much and buy a new leadscrew and nuts.
                              Whats better is to buy a set of digital readouts, and forget about the back lash.

                              if you don't want a DRO and will stay with handwheels, do this :
                              Use only the right hand side when feeding the table to the left.
                              Use only the left hand side when feeding to the right.
                              In essence, You only turn the feed handles CLOCKWISE
                              Here is the procedure-----
                              Start your job and bring the cutter to your start point say , using the left hand feed. Zero the left dial. Clamp the table ! Now move the right hand feed ( CW !) until you feel pressure . now zero out that dial !
                              Release the clamp and procede

                              True, you will be going back and forth to each side, but your hand dials will be in perfect sync ! The backlash eliminated from your calculations as the dials reflect .

                              To see how this works, say you were feeding the table using the Right hand side and you went .01" TOO FAR .
                              You have a choice, backup a turn and then try again, or go to the left side and just bring it to zero ( The left dial will show the .01 plus the backlash to get back to zero.
                              Backing up a full turn and coming in again, sometimes can't be done (long narrow pocket), but the duel hand feed use ....again, only neat

                              Last edited by Rich Carlstedt; 06-17-2012, 08:19 PM.