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How to keep a compression spring in a hole?

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  • How to keep a compression spring in a hole?

    Machinists,
    I have the need to keep a compression spring (.25" dia x 1" long) in a 3/4" deep hole while another piece of metal comes up and hits the spring, the pieces then is held in place by a sear, and when the sear is released the spring pushes the metal away.

    My question is how do I keep the spring in place inside the hole so it doesn't spring or fall out?

    I suppose friction fit would work, but looking for other ideas.

    Regards,
    Jimno

  • #2
    An easy solution might be a .255 or so plug of fairly still rubber, pressed to the bottom of the hole.
    Location: North Central Texas

    Comment


    • #3
      assuming the part with the spring has clearance and isn't much thicker than the spring is long.

      Make an internal spring guide shaped like a nail with a snap ring groove at the far end. The spring bore would be a deep c'bore with a clearance hole through, that will control the spring guide.
      The guide goes through the core diameter of the spring and out the backside of the part and the snap ring groove is set at the max length the spring is allowed to expand.


      Last edited by Rusty Marlin; 08-15-2007, 04:49 PM.
      Ignorance is curable through education.

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      • #4
        How about some very stiff grease?
        Gene

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        • #5
          Maybe an O-ring "threaded" onto the 1st helix of the spring and pressed fit into the hole?

          Comment


          • #6
            Remember that a compression spring expands slightly when compressed and size clearance hole accordingly to prevent binding.

            Also if the L/D ratio of a compression spring is too large the spring will try to buckle and bind in a hole or over a rod when compressed. Guide well and accept increased friction or substitute multiple shorter springs of suitably small L/D with ends closed and ground and separate them by washers.

            David Merrill

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            • #7
              I've made and sold about 500 of these little brass thingies that fit between two hooks on banjos:


              It works like a toilet paper roll holder, with an internal spring that's captured by friction at both ends so the parts don't separate when you take it off. On the part that receives the spring, I simply drill a stepped hole so the spring jams by friction only at the bottom 1/8" inch. That accommodates the compression/diameter change.

              Cheers,

              Frank Ford
              FRETS.COM
              Gryphon Stringed Instruments
              My Home Shop Pages
              Cheers,

              Frank Ford
              HomeShopTech

              Comment


              • #8
                Reread the question.

                You need to have the spring compressed.

                Can you drill a small hole across the bore to insert a piece of wire that would hold the spring compressed for assembly, then pulled out to let the spring expand?
                Gene

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                • #9
                  Frank, what's the purpose of your brass thingie for the banjo?

                  Sorry to hijack the thread.
                  West Sussex UK

                  Comment


                  • #10
                    Alan -

                    It's a little bracket that holds a small electronic tuner. The banjo teacher at our shop asked me to make him a gizmo to hold his tuner, and, well, things got a bit out of hand.

                    it’s spring loaded and squeezes in between two hooks on the banjo rim. It’s the right diameter for the small clip that comes with the Korg AW-1 tuner, so it holds the tuner at just the right angle for easy viewing as you play. Because the tuner is held in close to the rim, your banjo can go in and out of its case without removing the tuner. This adapter fits most open back banjos that have 1 1/4" to 1 1/2" of space in between the brackets. It also fits most resonator banjos with a cast flange that have 1 1/4" to 1 1/2" of space in between the brackets. NOTE: some resonator banjos with two piece or other bulkier flange designs may not fit or may require some modification of the tuner clip. To use the holder, you need to attach the clip first, install the holder on the banjo, and then slide the tuner onto the clip.

                    Here's the tuner installed:


                    Cheers,

                    Frank Ford
                    FRETS.COM
                    Gryphon Stringed Instruments
                    My Home Shop Pages
                    Cheers,

                    Frank Ford
                    HomeShopTech

                    Comment


                    • #11
                      www.springplungers.com

                      A whole website dedicated to spring plungers. I'm sure one of these will work.

                      Thanks to all.

                      Jimno

                      Comment


                      • #12
                        How to keep a compression spring in a hole?

                        Rusty hit the nail on the head. This is a common solution in tool and die and is used as a stripper to keep the part from sticking in the bottom of a form die. The shoulder bolt from the back side of the bolster will limit the travel as well as retain the spring.


                        Originally posted by Rusty Marlin
                        assuming the part with the spring has clearance and isn't much thicker than the spring is long.

                        Make an internal spring guide shaped like a nail with a snap ring groove at the far end. The spring bore would be a deep c'bore with a clearance hole through, that will control the spring guide.
                        The guide goes through the core diameter of the spring and out the backside of the part and the snap ring groove is set at the max length the spring is allowed to expand.


                        Jim (KB4IVH)

                        Only fools abuse their tools.

                        Comment


                        • #13
                          Frank,

                          That's pretty neat. I didn't know people were tuning banjos!

                          Kevin

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                          • #14
                            How about a small drop of epoxy in the bottom of the hole?
                            Paul A.
                            SE Texas

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

                            Comment


                            • #15
                              Kevin -

                              Strange as it may seem, banjo players actually believe they are making a substance called "music."

                              Now, at the extreme risk of posting an off-topic item, let me clue you into just about the coolest T-shirt ever:



                              Cheers,

                              Frank Ford
                              FRETS.COM
                              Gryphon Stringed Instruments
                              My Home Shop Pages
                              Cheers,

                              Frank Ford
                              HomeShopTech

                              Comment

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