how to make twist-lock connector?

I need a connector for a combined physical mounting and low-pressure pneumatic application.

The overall dimensions of the connector with the male and female parts mated needs to be less than 3/8" diameter by 1-1/4" in length. The male part needs to be 1/4" in diameter, ideally 1/2" long. There will be a 9/64" hole drilled through the connector to pass low-pressure air. The end of the male part needs to mate precisely with the bottom of the female part to prevent air leakage. I need to insert the connector and twist it to lock, and it has to lock at exactly the same place (rotationally) every time. The details of the locking mechanism aren't too important -- a bayonet mechanism with a stud is ideal.

I have no idea how to make such a thing. I have a lathe, mill, the usual power/hand tools.

Has anyone made a twist-lock connector of any kind? The bayonet style apparently has a complex slot machined by who-knows-what. Any clues as to how to make something like this would be much appreciated.

-- Renaissance Productions, Inc:

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If you can twist it thru several revolutions it's easy to just thread it. Even one thread will hold a lot in that small size.

Reply to
Nick Hull

What you don't say is if the connectors need to shut off when unmated, or what the acceptable leakage rate when mated is.

First off I would suggest you inspect the wares of the Clippard Corporation as they do make miniature air fittings of all types. They make a connector similar to the one you are proposing but it is screw-home type, not bayonette. It uses a schrader valve core to make it seal up when disconnected, and is 1/4 inch diameter roughly.

If you don't require the connector to shut off when unmated I would suggest you modify a commercially available electronics connector that is bayonette mount. I would immediately go to Trompeter Corporation's catalog as they make some of the best miniature bayonette mount connectors in the business. I am familiar with their minature triax connectors in particular. There's a large number of electronics connector companies out there and the trouble is that many of them have long lead times and large min orders. Trompeter stocks everything they sell.

I might also suggest you scan the McMaster Carr catalog - I seem to recall that they sell a bayonette grease fitting that is quite small. It's possible you could modify that with an o-ring seal to suit your application directly.

Good luck - Jim

Reply to
jim rozen

Threads won't work, Nick. The ending rotational position needs to be exactly the same every time -- threaded connectors vary based on tightness and wear. Granted a bayonet-type connector may eventually vary based on wear, but not (in my experience) as much as threads. Thanks though.

-- Renaissance Productions, Inc:

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No need for shutoff when unmated. Will try your sources, thanks.

-- Renaissance Productions, Inc:

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hint: the cam doesn't have to be inside the nut, it can be on the male part...

Reply to
Jon Grimm

It doesn't matter that the threads wear, you can still end in the same rotational position. I have a .22 rifle (browning take down)and the bbl comes off with a quarter turn and goes back on with a 1/4 turn (interrupted threads). There is a stop that makes it exact, the bbl probably has more need for exact alignment than your connector. It also has a take-up nut to compensate for any wear. Presumably you will be using some form of "O" ring for sealing anyway.

Reply to
Nick Hull

How is the stop constructed, Nick?

Unfortunately I have no room for take-up nuts within the physical space available. As for barrels having more need for exact alignment, I think probably not since the bullet doesn't care where the rifling starts and the sight can be off as much as a couple degrees and 99% of all shooters wouldn't notice, but I could easily be mistaken; in any case people will be checking these connectors with a loupe to see that it is exact, so it needs to be exact, and I am talking about significantly less than half a degree.

I'm not sure on that Nick. It depends on how well the thing seals without it. I will probably be using brass to make the connectors, and there are lots of brass fittings that seal perfectly. Once I figure out how to construct the basic connector I'll figure out what's next -- perhaps an O-ring, perhaps a Delrin end-piece, until I get the basics working it's pointless to guess about sealing.

I don't really have anything against threads aside from never having cut them and these will be pretty small (1/4" od). The "interrupted" threads thing seems like it would require some machining inside the female part to achieve the interruption? Depending on what kind of mechanism I can find to act as an exact "stop" I could go with non-interrupted theads, the number of turns to lock isn't nearly as critical as where it ends up.

Are there standard methods of achieving a precise top on threaded joints? It's something I've never noticed or paid attention to, time for some head-scratching.

-- Renaissance Productions, Inc:

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First off, look at a number of different styles of the connector that you want to do. They will give you the proper ideas for how they go together. The fancy slot is really easy to do. Start the cut at the end of the slot and go towards the top by 1/2 of the width of the cutter, rotate the work by so many degrees and then cut back down to the bottom. Repeat exactly 180 degrees (or 120 degrees if you want a 3 point one) and you have that fancy cut.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Reply to
Bob May

Interesting thought. You could take some of the Clippard disconnects and interrupt the threads on them, they would come up with a quarter turn or so.

Jim

Reply to
jim rozen

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