Announcement

Collapse
No announcement yet.

Threadlockers ...but not too tight!

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Threadlockers ...but not too tight!

    This past weekend, for the second time my Stihl chainsaw lost the roller-bar tensioning screw. I suspected something wrong when suddenly the chain flung loose and wrapped around the back of my hand. ...Ooops! (it was really more like "Holy Sh*t!") Fortunately, not even a scratch.

    Is there one of the Locktite adhesives that will work well to make that screw less prone to vibrate out, YET still permit freely turning it to tension the bar? Or for that matter any other compound or trick that I might use?

    The screw fits into a sliding, round, special purpose tensioning nut that engages a hole in the bar to achieve the proper tension. So a locking nut is not an option in this case.

    This is a fine thread metric screw ...slightly smaller than a UNF #12. (sorry, I'm not real fluent in metric sizes)

  • #2
    <font face="Verdana, Arial" size="2">Originally posted by lynnl:
    (it was really more like "Holy Sh*t!") Fortunately, not even a scratch.
    </font>
    "Holy Sh*t" is right! Can I touch you for good luck next time I go pick out lottery numbers?

    The curse of having precise measuring tools is being able to actually see how imperfect everything is.

    Comment


    • #3
      That event sounds like one of things I'll add to the list of things I least want to have happen to me.

      There's dozens of different types of Loctite thread locking products. The Loctite web site ( www.loctite.com I think) ought to have the information you need, although the last time I went there I found it not to be the easiest website to navigate that I've ever seen.

      As a make-do alternative, you might try some plain old Silicone sealer.
      ----------
      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie

      Comment


      • #4
        It sounds like you need a screw that contains a nylon pellet or a nylon patch. Here's a description: http://www.accuratescrew.com/Optiona...-Features.aspx

        I looked in the Reid Tool catalog & they have these in inch sizes only, no metric. A large fastener warehouse may be the best place to try.

        ------------------
        Barry Milton
        Barry Milton

        Comment


        • #5

          You can try RED locktite, but you can also count how many threads are going in, back out the screw, then crush a few of the last threads with a pair of needle nose pliars and re-install the screw..

          The last few threads you crush will cause the screw to bind up a little at the very end holding it in place...

          When I say "crush" the threads, I mean just crimp them enough to cause some distortion, etc.

          -Adrian

          Comment


          • #6
            Hmmm.. Crushing the first few threads sounds like it might serve my purpose. I need to retain most of the full range of adjustment, since new chains stretch quite a bit over time, as they also do under prolonged use, as they heat up.

            After posting my original question I now recall that this most recent screw lost was not a genuine Stihl replacement part, but rather just a screw that I found in my coffee can of miscellaneous nuts and bolts. It'd only been in there for maybe 2 or 3 hours of total useage, whereas the original screw stayed put since I bought the saw in about 1985 ...probably over 100 hrs use. Yesterday I bought a couple of the real McCoy's from a Stihl service center. Maybe they're a tighter class fit.

            (??? Do metric fasteners have varying class fits similar to the SAE or Unified standards???)

            I think the reason I wasn't cut is because the chain kind of flopped sideways as it ran across the back of my hand. And once the tension and sprocket engagement was lost it stopped moving almost immediately. Regardless, I'd just as soon not repeat the experience.

            Comment


            • #7
              If your bar loosened up enough for the chain to come off the adjusting screw is not the problem. It does nothing to hold the chain/bar in tension. Your bar clamp bolt may be loosening due to vibration. Your obviously no strainger to using a chain saw and I don't mean to imply that you are. One thing I would check would be the clamp bolt itself, inspect it for stretching of the bolt or the threads are stretching, or the nut.
              Paul G.

              Comment


              • #8
                Paul, you're certainly correct about the function of the clamp bolt/nut to hold the bar tightly in place, once it is tensioned properly.

                But that sliding nut, with a protrusion that engages a hole in the bar (just forward of the sprocket) would tend to help resist rotation of the bar around the axis of the clamp bolt, which would affect the tension.

                After the incident, the clamp nut certainly seemed to be plenty tight enough. I'll never be sure of the exact cause, but it may well be that the chain just stretched enough to jump the track.

                I had checked it before starting to saw, as I always do, and it seemed to be 'exactly right' then. when it happened I'd worked about 45-60 mins, felling, limbing and bucking one tree, and kinda cleaning debris as I went. I remember monitoring it visually once or twice, and though looser it still seemed acceptable.

                Comment


                • #9
                  I would try an trick from an oooooold motorcycle restorer.Get some thin nylon fishing line,cut a piece,and stick down hole.Now thread in bolt,and you have your very own self-locking bolt.Don't know how it would stand up to the vibrations from a chainsaw though,so test carefully!

                  ------------------
                  Hans
                  Hans

                  Comment


                  • #10
                    If I am not mistaken the stihl should have two clamp screws that hold the bar in place. My 038 does. I have had the chain jump off the bar seveal times usually when cutting brush. Lucky it has never come around and hit me. You are lucky to have not been injured, which I am sure that you know.
                    Charlie
                    Don\'t ask me to do a dam thing, I\'m retired.
                    http://home.earthlink.net/~kcprecision/

                    Comment


                    • #11
                      another trick to use is get some bowstring wax for archery and put it on the bolt threads it will dampen vibration and is sticky enough not to back out, but will permit ease of movement--use it all the time for applications like that...

                      Comment


                      • #12
                        <font face="Verdana, Arial" size="2">Originally posted by lynnl:

                        (??? Do metric fasteners have varying class fits similar to the SAE or Unified standards???)
                        </font>
                        In reply to chains stretching, the stretch temporarily do to heat but permanently due to wear, the pins etc. wear and make the chain longer.

                        In reply to metric fits anyone who's worked on an American car with metric fasteners would know that a 1/2" wrench will fit a 13mm bolt or nut. This is not the case with quality German stuff like Stihl saws or Porsche engines. Example the distributor nut on a 911 is 13mm and is in such a tight place that a distributor wrench like those made for a Chevy is the best bet for adjusting it, however you must first file each flat on the wrench a bit or it simply won't fit, when Porsche calls for 13mm or similar they mean it, the tolerances are very close. My guess is the original screw was what I refer to as "true metric" and the replacement was "american metric" which seems to have a looser standard.



                        ------------------
                        -Christian D. Sokolowski

                        Comment


                        • #13
                          lynnl --

                          ND Industries makes a product named Vibra-Tite that amounts to a brush-on lockpatch for screws. Unlike conventional anaerobic thread locking compounds (Originally developed by Loctite, and are what most of us think of when we hear the name Loctite even though today's Loctite Company makes and markets MANY chemical products that are not anaerobic thread locking compounds), Vibra-Tite contains a solvent and must be allowed to dry before installing the screw.

                          To use Vibra-Tite, you simply brush it onto the screw and let it dry. Then install the screw. A Vibra-Tited screw can be reused or readjusted pretty much at will without having to reapply the Vibra-Tite.

                          I particularly like using Vibra-Tite on adjustment screws, and am still using a 1 ounce bottle of Vibra-Tite that I bought years ago, and if I recall correctly I paid about US$ 25 for it from a fastener supply house.

                          John

                          Comment


                          • #14
                            Might try that bowstring wax trick. It will have to withstand continuous exposure to the bar/chain oil though, because the auto-oiler port is just above this tensioner.

                            Charlie, the bar on this saw (stihl model OV 011) is clamped down by only one nut which clamps the side cover down tight against the bar. That nut threads on to a stud which is positioned within a slot in the back end of the bar. I also had been most recently cutting small limbs and brush-like stuff, but at the moment it came off wasn't actually cutting but just rev'ing up prior to making a cut.

                            John, just now saw your comments about the Vibra-Tite. That sounds like a very useful product for many such applications like this. Any idea how durable the stuff is? ..in terms of time, chemical exposure, mechanical abrasion, etc.? $25 sounds a little steep, but then I'm still on the one little tube of red Loctite I bought (12-$14) 10 or so years ago. I keep it refrigerated and it seems as good as day one. So I guess if you amortize the cost over the years and numerous applications, $25 is still a bargain.

                            [This message has been edited by lynnl (edited 05-04-2005).]

                            Comment


                            • #15
                              lynnl --

                              ND Industries sales flyer for Vibra-Tite can be found on the web at:

                              http://www.ndindustries.com/html/Ind...f/Vibratdc.pdf

                              I've been very happy with the performance of Vibra-Tite'd fasteners in the presence of oil, water, and grease and atmospheric temperatures and pressures. It hasn't ever fallen off of anything I put it on, deliberately or inadvertently. But, since the fluid product contains MEK as a solvent, Vibra-Tite isn't going be suited to a ketone-laden environment.

                              Overall, I like it. Thumbs up!

                              John

                              Comment

                              Working...
                              X