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Keeping Screws Tight

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  • Keeping Screws Tight

    I'm working on a project which requires a small dovetail with a gib.

    I tapped three holes for a 4 - 40 thread for which I had some set screws to adjust the gib.

    But when I went to put in the screws, these wonderful Chinese made items didn't fit in the holes. They are about .001-.002" larger than the size of the tap. I then went to a store here, but Brazil does not have much in a 4 - 40 size, so they didn't have anything.

    Next, I found some longer 6 - 32 screws, retapped the holes and cut little sections of the screws, put a slot in them and presto. Except these are a really sloppy fit.

    I don't have room for a nut to adjust so I need to know if there is some kind of LOKTITE or silicone or something to hold these screws more firmly so that the gib adjustment will stay put.

    Any ideas??? I know I've come to the right place. Somebody has got to have faced this before.
    Vitَria, Brazil

  • #2
    If the screws are not subject to oils, use 3M weatherstrip adhesive...AKA gorilla snot. It's what GM used on main bearing bolts to keep them tight.

    It will tolerate motor oil after it is dry..but not CRC or such. The adhesive will hold the screw from turning but it will let you adjust it if needed. Just put a coating on the male threads and run them in.

    Comment


    • #3
      If you have the depth, run a second screw down onto the first to lock it into place.
      I wouldn't use locktite on that small of a screw unless it was seldom going to be moved.
      A small dab of fingernail polish on just a couple threads of the screw would work as well.
      I cut it twice, and it's still too short!
      Scott

      Comment


      • #4
        I guess you could use the wicking Loctite..it's green I think. It's made for keeping things from moving on their own, but can be adjusted or removed with hand tools.

        Comment


        • #5
          Check out this thread over at PM. I used the locknut method on an old South Bend lathe cross-slide but I had to buy some all-thread and make longer screws first. The "nylock" method is more elegant and could be appropriate if you don't have room for locknuts.

          http://www.practicalmachinist.com/vb...-style-154334/


          Also - McMaster sells self-locking screws that have a nylon patch.

          Tom
          Last edited by flathead4; 09-01-2011, 02:25 PM.
          Tom - Spotsylvania, VA

          Comment


          • #6
            We are frowned upon by some at PM...

            Comment


            • #7
              File a groove the long way with a knife edged needle file, down to the thread root. Stick a piece of monofilament fishing line in the groove with your favorite sticky substance.

              Joe

              Comment


              • #8
                Originally posted by Optics Curmudgeon
                File a groove the long way with a knife edged needle file, down to the thread root. Stick a piece of monofilament fishing line in the groove with your favorite sticky substance.

                Joe
                Now that one I liked. Anything that has to do with fishing has got to be good. There are several others I think will work too.

                No room for lock nuts.
                Vitَria, Brazil

                Comment


                • #9
                  Take a piece of a plastic bag and put over the hole, then thread the screw in.

                  Comment


                  • #10
                    There is (or was) a variety of Loctite just for this application. It was to act as a "shakeproof" feature, not really glue the fastener in solid.

                    That being said, some of the other suggestions such as fishline nylon insert are easy and cheap.
                    .
                    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

                    Comment


                    • #11
                      You could just make your own screws. This is the very first item I made when I got my SB9.

                      It's 6-32.

                      Free software for calculating bolt circles and similar: Click Here

                      Comment


                      • #12
                        Originally posted by Optics Curmudgeon
                        File a groove the long way with a knife edged needle file, down to the thread root. Stick a piece of monofilament fishing line in the groove with your favorite sticky substance.

                        Joe
                        That actually is a good suggestion. been there, done that.
                        Also, most good hardware stores have the set screws with the nylon blip
                        already in place.

                        Something else you may try. A quick wrap of teflon tape on the screw
                        prior to install.

                        Comment


                        • #13
                          Originally posted by Patch
                          Also, most good hardware stores have the set screws with the nylon blip
                          already in place.
                          Actually, that's perhaps my major problem. Many, many items which I took for granted before are hard, or even impossible to get.

                          Try finding a nylon/plastic screw for example. No one here has even heard of them.

                          Today I was trying to find some thread dies. A 5/16-20, a 1/4-24 and a 3/8-20. In a city of 1.5 million people, the stores claim that there is no manufacturer. They just don't exist here, or if they do they are imported. It is probably that in Sمo Paulo, a city of over 30 Million people, there would be something some place.

                          Anyway, there are lots of challenges. I tried to move as much equipment as I could imagine I would need, but you always miss something.
                          Vitَria, Brazil

                          Comment


                          • #14
                            Originally posted by davidwdyer
                            I'm working on a project which requires a small dovetail with a gib.

                            I tapped three holes for a 4 - 40 thread for which I had some set screws to adjust the gib.

                            But when I went to put in the screws, these wonderful Chinese made items didn't fit in the holes. They are about .001-.002" larger than the size of the tap. I then went to a store here, but Brazil does not have much in a 4 - 40 size, so they didn't have anything.

                            Next, I found some longer 6 - 32 screws, retapped the holes and cut little sections of the screws, put a slot in them and presto. Except these are a really sloppy fit.

                            I don't have room for a nut to adjust so I need to know if there is some kind of LOKTITE or silicone or something to hold these screws more firmly so that the gib adjustment will stay put.

                            Any ideas??? I know I've come to the right place. Somebody has got to have faced this before.
                            Thought a little more about what you are trying to do:

                            Knowing you now are using a straight slotted screw without the head in lieu of a set screw;
                            with an assumed thread bore depth that prohibits the use of 2 set screws back to back to lock them in place; and without ample clearance such that a screw with a hex head cannot be used with a jam nut; I give you a last try to perhaps help solve the problem.

                            Firstly, I am assuming since you cut a slot in the bolt shank there is sufficiant room to use a flat bladed screwdriver to install the set.
                            Since you made mention that a jam nut, due to clearance cannot be used, I suggest you make a jam tube then.
                            Let your jib screw set be several threads longer than the bore depth.
                            By this I mean, the threaded shank of the set bolt will protrude to the outside of the bore perhaps 1/4".

                            Using a piece or round stock, perhaps 1/2" long or more,(?)- drill thru and tap I.D. to set bolt thread size. It is important to keep the cylinder longer then the protrusion of the set bolt you are using.
                            Slot the cylinder just as you did for the bolt shank.
                            Thread the new cylinder to a bolt of length and chuck it into your lathe.
                            Turn the outside of the cylinder down (reduce diameter) such that it will after threading onto the set shank screw bolt clear any surface when fit.
                            My guess would be that the cylinder may have a wall thickness of say, .050"
                            That is sufficiant.

                            To use:
                            Install gib screws and adjust pressure.
                            Install threaded cyl. over the 1/4" extension of the gib screw using a screw driver tighten the "JAM (nut)Cylinder" snug.

                            Hope it helppppsssssssssss,

                            On edit: forgot to mention similiar to monofiliment fishing line,
                            for large or larger bolts, provide a milled slot and use weed trimmer line.
                            It comes in a variety of different diameters from .045 to .095 and larger.
                            Works great.
                            Last edited by Patch; 09-02-2011, 12:14 AM.

                            Comment


                            • #15
                              Originally posted by Optics Curmudgeon
                              File a groove the long way with a knife edged needle file, down to the thread root. Stick a piece of monofilament fishing line in the groove with your favorite sticky substance.

                              Joe
                              I have used fishing line. I don't bother with filing a groove, just place a loop in the hole and then the screw. The two lenghts, one in and one back out, seem to lock screws just fine.

                              Of course, if you remove the screw, you must replace the fishing line.
                              Paul A.
                              SE Texas

                              Make it fit.
                              You can't win and there IS a penalty for trying!

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