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Slitting Across A Hole For Expansion

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  • Slitting Across A Hole For Expansion

    I'm working on the weights for my balancing hubs. Today I drilled and tapped one for the 1/16" NPT plug.
    It took a little more force in tightening the set screw than I thought it would to expand the weight secure it in the groove.
    I'm thinking I should cut the slot a little further. Is there a rule of thumb for stuff like this???? Or is it just trial and error.
    The weight in the picture is a test piece. I want to make sure I get it right before I slit the good ones.
    I could move the hole a little further to the right which would give me more room to slit past it on the left.
    As it is now, if I take the plug out and squeeze the weight I can't get it to close up at all, so it wold be just as hard to expand.



    I can set it back up and slit it a little further.

    JL..............


  • #2
    Putting the threaded hole further to the right would certainly help. Plus drilling a smaller size hole that is 3 or 4 times the diameter of the slitting saw thickness near the other face would help as well. Get the smaller hole close enough that you can flex the slit by hand pressure to a visible amount. For the first one if it's still too strong you could use a round file from the outside to reduce the width of the web until it will flex a little by hand. Then make the webs on the rest the same thickness.
    Chilliwack BC, Canada

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    • #3
      That's what I was trying to say...... it's doesn't have any flex. I can squeeze the weight as hard as I can between my fingers and I can't get the slit to close up. I think cutting the slit a little more past the hole would do the same thing as drilling a small hole.

      Looking at some of the manufactured ones I can see that the slit is closer to the end of the weight. I'll try cutting mine a little more until I get some flex with moderate force.

      JL................

      Last edited by JoeLee; 05-22-2017, 08:10 PM.

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      • #4
        Drill a hole, it looks better. Things can go wrong reslitting.
        After drilling you may be able to hacksaw it.

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        • #5
          What material did you use, brass? It is hard, doesn't want to bend much. Steel bends readily, as will aluminum, lead and others.
          Amount of experience is in direct proportion to the value of broken equipment.

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          • #6
            Originally posted by Jaakko Fagerlund View Post
            What material did you use, brass? It is hard, doesn't want to bend much. Steel bends readily, as will aluminum, lead and others.
            Steel has twice as much "stiffness" or Young's modulus compared to brass.
            Average brass and steel are quite similar in both yield strength and ultimate tensile strength.
            Location: Helsinki, Finland, Europe

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            • #7
              Originally posted by Jaakko Fagerlund View Post
              What material did you use, brass? It is hard, doesn't want to bend much. Steel bends readily, as will aluminum, lead and others.
              The material I used is 932 bronze. It doesn't have to flex much. The weights are a real close fit in the groove, probably .0005 or less, hand fitted.

              JL................

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              • #8
                Just throwing this out but you could anneal the existing piece so it is dead soft. You aren't really looking for repeatable "spring" since the piece will be set and locked once it is in the right location.

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                • #9
                  I never thought of that. Didn't know it could be "un-tempered" so speak. What temps would I need to achieve this ??
                  It doesn't have to move or expand much to lock in place, a few tenths to a half thou at the most.
                  I was thinking of bead blasting the inside walls of the groove and the top and bottom sides of the weight to help make it stay in place when locked down. The thought of one of them flying out scares the hell out of me.
                  But in doing that bead blasting may warp the hub slightly and that type of finish in the groove would make it more difficult to wipe clean when the weights had to be re-adjusted.

                  JL...................
                  Last edited by JoeLee; 05-23-2017, 11:56 AM.

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                  • #10
                    Another advantage of the drilled hole, less prone to cracking. Extend the slot, with or without hole....should be two fingers on the allen wrench to tighten it up

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                    • #11
                      I don't have any formula or rule of thumb for how much a slotted part will flex but I wouldn't be surprised if some people who do that all the time had one. I can't offer anything better than trial and error.

                      I like the idea of a drilled hole at the end of the slit. The square corners of your saw cut slit will act as stress risers and are the obvious point of failure. As well as establishing the distance easily, a round hole will distribute that stress more evenly around it.
                      Paul A.
                      SE Texas

                      And if you look REAL close at an analog signal,
                      You will find that it has discrete steps.

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                      • #12
                        Originally posted by JoeLee View Post
                        I never thought of that. Didn't know it could be "un-tempered" so speak. What temps would I need to achieve this ??
                        It doesn't have to move or expand much to lock in place, a few tenths to a half thou at the most.
                        I was thinking of bead blasting the inside walls of the groove and the top and bottom sides of the weight to help make it stay in place when locked down. The thought of one of them flying out scares the hell out of me.
                        But in doing that bead blasting may warp the hub slightly and that type of finish in the groove would make it more difficult to wipe clean when the weights had to be re-adjusted.

                        JL...................
                        Brass can be annealed by bringing to a range approaching 1400 F then dropping the part into a cup of water. The material should appear a dull to medium red under normal shop conditions (i.e., not in bright sunlight). You could certainly achieve this with an oxy-acetylene torch and many air-propane torches will reach/exceed these temps.

                        Annealing link:

                        http://www.nancylthamilton.com/wp-co...for-Metals.pdf

                        Heat colors link:

                        http://www.stormthecastle.com/blacks...ring-chart.htm

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                        • #13
                          The other advantage to the hole is on thicker parts, when you slit from both sides.. Easier to look even, even if you finish slit with a hacksaw.
                          Motorcycle triple trees..or slab yokes as some call them...are a perfect example..

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                          • #14
                            Bead blasting won't warp your part.

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                            • #15
                              Take a look at the threads on the plug your screwing in there. Are the threads nice and smooth or a bit rough? You might find the rough threads are part of your problem...

                              lg
                              no neat sig line
                              near Salem OR

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