Detent Ring? Spring Ring? Non-Permanent Retaining ring? Help!
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  1. #1
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    Default Detent Ring? Spring Ring? Non-Permanent Retaining ring? Help!

    So, normally I am really good at finding stuff, but this time I have run into a roadblock.

    I am designing/trying to improve a thing. This thing reciprocates, is made of steel, and has 3/8" diameter by 1/4" deep pockets on it, and this pocket has a steel handle stud that fits into it and has an Aluminum housing around it that prevents the handle from falling out completely. The factory design uses a tiny magnet to hold the handle stud against the reciprocating steel component. However, the magnet is very weak, and the handle tends to separate from the reciprocating steel part during operation, and marr/gouge/burr the aluminum housing. The handle needs to be able to be pulled out for servicing and preferably without tools. An "improved version" was released by the factory, but it was crap, and instead of marring outer housing (which is mostly aesthetic, tbh), the handles were threaded in and had a nasty tendency of breaking off and leaving behind a difficult-to-remove threaded stud in the reciprocating bit.

    I want to solve that, and I have come up with a solution, but I cannot for the life of me figure out what it would be called to get parts for making the changes. However, I have found something that does exactly what I want to do:

    Are you all familiar with the drive end of an impact driver? Generically speaking, you have a shaft (the square drive) that has a groove in the end. In this groove you will find a steel split friction/detent ring that is larger than the shaft, and sometimes backed up by an o-ring (for extra springiness, or just to center it?). It mates with a housing (the socket) that also has a groove in it, that the split friction/detent ring seats into. When the housing and shaft are pressed together, the ring compresses until it reaches the groove in the housing, then springs open and hold the two parts together, firmly enough that they don't fall apart, but light enough that the shaft can easily be removed from the housing.

    Another example of the exact same principle is a snap button on clothes. You have housing that contains a split ring, and a shaft is pressed into it, spreading the ring over the tip, and into a groove, fastening the two parts together, but still easy to detach.

    That. I want that to be the solution. Does that kind of assembly/system have a name? Can you buy off-the-shelf parts from someone to achieve exactly that principle for given sizes? I've searched every type of ring-like detent, friction, retention, holdy thing I can think of, but I just can't find that application. Most "snap rings" are meant for "permanent" installation, and not for people being able to yank stuff apart readily without tools. Fortunately, the size I am working with is 3/8", so I could actually just get the 3/8" impact driver retaining ring and apply that, but it would be nice to be able to apply it to other sizes for other purposes if need be, and for lower cost.





    It's for the charging handle of a WK180 rifle up here in Canada, for anyone interested on what I'm on about.

  2. #2
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    How about a ''snap ring'' snap ring - Google Search

  3. #3
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    Inexpensive holders for the common 1/4" hex screwdriver et al bits frequently use a simple ball and split spring ring device to hold the bits in.

    The retaining ball sits is a partially drilled hole so it projects into the the 1/4" hex hole but cannot fall through. The ring simply wraps round the holder keeping the ball in place. There is a hole a little less than the ball diameter in the ring to locate it on the ball. Usually the ring also sits in a groove to improve location.

    I've seen a similar device used with three balls for more secure location. No idea what they are called but a long time ago I found a source. Unfortunately for very large numbers only. I needed about 10 for a demo job and ended up using a spring type hose band clamp which just happened to have a suitable hole to retain the ball. Clipped the spring ears off an called it good. One day I shall find a use for the other 90 in the packet! At about a ha'penny each plus postage the financial waste is bearable.

    I see no reason why the same principle shouldn't work in reverse with the ring inside and the ball projecting outwards if you need it to work the other way round.

    ball.jpg split.jpg clamp.jpg

    Clive

    PS On post posting reflection it occurs to me that a simple close coiled spring might restrain the ball(s) well enough whilst still allowing sufficient movement.

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    Round wire retaining ring? They can be custom made to suit application, including spring tension values.

    Round Wire Retaining Rings & Snap Rings | G.L. Huyett

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    I'll say this much....half of the tools I own with those round retaining rings...the rings are broken and gone.

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    This is the best solution I have found for pins and things that work and don't fall out or wear out. I use them all over the place now. It may not answer your need but it looks like it might. The release is just a shaft that has a groove cut in it and a spring at the top. They are very positive. I know it's a little extra work but is also a very elegant fix.


    pin.jpg

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  8. #7
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    Quote Originally Posted by crossthread View Post
    This is the best solution I have found for pins and things that work and don't fall out or wear out. I use them all over the place now. It may not answer your need but it looks like it might. The release is just a shaft that has a groove cut in it and a spring at the top. They are very positive. I know it's a little extra work but is also a very elegant fix.


    pin.jpg
    I was about to recommend exactly this. Common on sailboats to fix sails to the halyard and/or foot, definitely a must-hold-but-tool-less operation.

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    I looked online but couldn't find info on anything except the threaded charging handle.

    What size is the magnet and is it in the handle or bolt carrier? I was wondering if it could be replaced with a more powerful one of similar size.

    The round wire snap ring would work but have you the means to cut a suitable groove for it?

    A picture of the charging handle would help.

    PS: If you have machining ability perhaps make a replacement charging handle that has a split section that would expand into the carrier recess. If you made the the knob 2-piece with the outer part threaded it could be used as a clamp knob to tighten loosen the expanding section. You would need a friction patch so it wouldn't loosen accidentally.

    Look at a concrete expansion anchor to get an idea how this would work, basically same as an expanding mandrel used in machining except the taper would be at the other end.

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    McMaster-Carr

    You can find similar at Carr Lane

    Alignment Pins | Carr Lane

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    I've never seen those pull pins sold that small.

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    Some of them are quite small. Here is an example of 1/4" ball lock pins.

    Ball Lock Pin: Button Handle - Jerico, Inc.

  13. #12
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    Not familiar with that model but after taking a look at the newer manual I think it is a bit clearer.

    If I understand correctly there is a collar o the charging handle that fits in that 3/8" recess and can only be pulled out when at the larger circle at one end of the slot. When the pin walks out of the recess it mars the inside of the aluminum receiver.

    Normally, in something like a blow-back arm spring tension prevents the pin from being pulled out until the spring is removed but that is not the case here. It appears the threaded handle was a much needed fix and the breakage may be happening to those who over-torque it. The manual says install hand tight and then a partial turn with a tool.

    One big issue is that any mod you make can not significantly alter the reciprocating weight or functioning may suffer. I think the round wire spring ring idea has merit but you'll need to cut an appropriately sized groove and perhaps very lightly chamfer the edge of the recess to ease insertion.

    PS: I'd suggest you ask the mod to close this thread and then re-post in the gunsmithing forum where there is more specialized expertise.

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