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Lead Screw Nuts

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  • Lead Screw Nuts

    Well I've just put parts of the this Fritz Werner together.
    It's apparent that there's no way of adjusting the lead screw nuts.
    on the "y" axis... I have a quarter of the dial slack.........theres no actual wear on the lead screw the slack must be in the nut.
    but the nut is a solid piece of brass with no slits etc.
    I know that this slack does not really make the machine's just an inconvenience.
    Should I decide to modify the nut in future do I do it .......meaning how do I put slits into it so that it can counteract the free-play.
    Have any of you guys got pictures of lead screw nuts with these slits in I can see how it's done.
    Does this modification last...or will it cause more wear.
    Do you guys consider altering the nuts a botch. ?
    Because of the age and obscurity of the machine there's not the slightest hope in hell of obtaining new nuts for it.
    all the best...mark

  • #2
    Mark; it is hard to tell you how to adjust the nut with out seeing a pic.of the problem.

    Some of the adjustable nuts has a cut at 90* to the screw and two screws pushing on the ends of the nut and a screw in the middle of the nut holding it in place causing the nut to bind on the screw threads. By adjusting the amount of binding it adjusts the amount of back lash.

    Others have a block that has two pieces that are threaded on the OD that screw into the block. The two pieces are also threaded on the ID to fit the lead screw.

    The two pieces screw in or out to take up the slack that developes between the lead screw thread and the nut thread.

    Here is a link in the US that has nuts and threaded bars for unique uses.

    I am not good at writting explations so hope that this is unstanderable.
    Don\'t ask me to do a dam thing, I\'m retired.


    • #3
      Emco Maximats of various sizes have a slit nut on their cross slides. It is slit thru the pitch diameter and a bit more, about 1/5 of the length of the nut, from one end. The slit is engaged by a single point cone set screw from the top of the cross slide.

      On Harrison, there are two nuts, one longer and one shorter, and a physical gap between them. A set screw from the top of the cross slide pushes a small wedge shaped bar between the two nuts to create an adjustable separation. The front and rear nuts are retained after adjustment with socket cap screws from above.

      I've seen others which have a 2nd section of nut with external thread into a threaded bore on the main nut, larger in diameter than the lead screw so as to encase it.

      Altering the nut a botch? Not if Emco and many others can do it at the factory You can do every bit as good a job as they can.


      [This message has been edited by nheng (edited 10-29-2005).]


      • #4
        I say fix it. First find the part of the lead screw where it is the tightest before doing anything. Then cut the nut in half so you have two shorter nuts . Half may not be possible depending on how it is mounted, on a SB9 cross slide nut you can manage about 70/30. Put the nut halves back on the lead screw where it was tightest and wind them together until it has no backlash. Mark the relationship between the halves. Take it back off and drill and either pin the halves or fit a small screw to hold them in that position.
        Free software for calculating bolt circles and similar: Click Here


        • #5
          First make sure the slack is due to the nut. The leadscrew is attached to the table (or whatever) by a thrust bearing. Slop in this bearing setup will behave like a worn lead screw. I suggest this because 1/4 turn is quite a lot.


          • #6
            Greetings Mark!

            Yonks ago, I had a worn leadscrew nut which was of the non adjustable variety.
            At the recommendation of my old tutor, I tinned it with solder paste.
            Before further howls of complaint arrive, I have to report that the leadscrew was in good condition and that screwing the nut on developed more muscles than before!
            Tinning assumes that the thing is brass or bronze rather than than Chinky metal- zinc alloy to most of you.
            Myfords use something similar for their feedscrews and I was able to take up that bit of wear by simply squeezing the worn nut.

            Neither of the foregoing are substitutes for a properly made replacement nut- but they work.

            I hope that these tips may help you and others who have problems with their nuts!
            Mine are past repair!




            • #7
              Cough!! just checking

              Thanks for the question Mark and nice work there
              More good advice, thanks men.



              • #8
                We need pics of the nut and mounting.
                Many ways to make adjustable nuts and many manufacturers did build them into their designs.
                Some are crude, 1/2 a split and a screw to close it which also tilts the thread to spring compensated 1/2 nuts.
                All work, some better than others.

                sir john.

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


                • #9
                  Well it's as simple as this ..SEE PIC BELOW
                  Nut has a collar on one side and locknut on the other.
                  Evans idea sounds like the most promising.
                  Normans sounds good as well..........but don't know bugger all about soldering ....and I may bugger it up.

                  All the best.....mark

                  [This message has been edited by aboard_epsilon (edited 10-30-2005).]


                  • #10
                    Praise indeed- muchas whatsits!

                    Soldering- a la me is dead easy!
                    Go buy a small bottle of solder paste.
                    This is an acid flux with powdered tin in suspension. The subtle bit is being acid it beats as it sweeps as it cleans! Or the flux will remove the s*** which defeats the final result.
                    This is not for doing fresh water supplies or electrical joints- so note!
                    Without teaching you how to suck eggs- practice on a bit of sheet brass, tinplate or whatever. Clean the plate with a bit of steel wool until most of the crap is off.
                    Apply the solder paste onto the bit in question. Have a clean bit of paper towel or bog roll handy. Gently warm up the solder paste until you see little beads of
                    silver appearing on all the test bit.
                    Remove the heat source and put it out of mischief and wipe the remains of the paste off.
                    You should have a bright and sparkling bit
                    of tinned metal. You can't quite do this with a nut but you should see a thin even film of new solder. If you ain't, cool and clean and start again.

                    With your newly aquired proficiency, you can move on to say leading a bloody big dent in a car wing. Off you go to the garage suppliers or the local plumber wholesale and buy some wiping or body work solder and some tallow- or vegetable oil.
                    Armed with a wool cloth soaked in it, you can gently warm up the oiled end of the stick until it just begins to melt and you introduce it to the recently tinned bit of metal and keeping up only sufficient heat you can do all sorts of moulding.
                    Now, Mark, don't get the idea that any old stick of solder will do cos' it will run like- well?

                    You can do all this lark with silver solder paste and silver solder but first things first-Eh?

                    My old- and very missed tutor taught me to do it still in his best suit, shoes and college tie.

                    For a bloke who has sea water in his veins, it is useful thing to be able to do.

                    Have fun.



                    • #11
                      <font face="Verdana, Arial" size="2">Originally posted by aboard_epsilon:
                      Well it's as simple as this ..SEE PIC BELOW
                      Nut has a collar on one side and locknut on the other.
                      Evans idea sounds like the most promising.
                      Normans sounds good as well..........but don't know bugger all about soldering ....and I may bugger it up.

                      One way.
                      Mill a keyway along the length of the nut, 3/16" x 3/16" [ guessing] drill two holes in the housing to match up with the keyway, better if you can get 4 in, two at the flange end and two at the nut end.
                      Then just cut the nut in two in the middle.

                      Fit the two pieces of nut as if it hadn't been cut and secure the flange end with the two grub screws with ends turned to fit the keyway.
                      Do the same the other end but just nip the cut nut.
                      Fit leadscrew and tighten the locking nut to pull the two halves apart to take out the backlash.
                      Tighten the two remaining screws.

                      Job done, go make a coffee.

                      Sir John.


                      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


                      • #12
                        Thanks john ..
                        that sounds as much work as making a new nut from scratch........think i will have a go at making a new nut
                        all the best..mark


                        • #13
                          One keyway, two or 4 tapped holes, one sawcut.
                          Probably took as long to type the original reply as do it.
                          Half to threequarters of an hour max.

                          You are looking at one to two hours to make a new nut.

                          Up to you,

                          John S.

                          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


                          • #14
                            What if..............

                            the shoulder was turned off the nut & then an external thread cut to duplicate the other end.....then slit the nut on one side lengthways with a very thin saw.....make up another lock nut exactly the same as the existing one......when fitted and the lock nuts tightened evenly would the angle of the external threads not tend to "close down" the nut onto the leadscrew threads ?

                            Just a Sunday afternoon musing with no thread specifications to hand so I dont know if there is enough clearance in the root to accomodate this.

                            Sunday evening pint time....doubtless by the time the second pint of Speckled Hen has slipped down I will have realised the errors of musing before drinking.




                            • #15
                              MUST have been dreaming
                              actual backlash in handle is about 1/8 ish of a turn........this is indicated as 0.025 inch.
                              one revolution of the dial is 0.2 inch.
                              is this amount of play OK is 0.2 inches per revolution normal for cranks.
                              all the best.mark