Making a collar

[polished54]

Hi! Recently I've bought some stainless steel rods to some other project and now I have a few pieces left. I came up with an idea to make a steel locking collar out of it. You know, in the style of Eternity collars or similar. It would require some bending and other things, but I'm familiar with those. The lock itself would be simply a hex screw. But what about hinge? I thought they use a rivet, but the classic rivet would stick out on both sides, and if you look closely you see that one side of the collar is smooth while the hinge rivet is visible only on the other side. It seems that rivet is not placed through the whole diameter of the rod but it's somehow secured inside. I'm lost right now. Apparently there are some gaps in my technical knowledge

So here comes the question: does anyone knows how to make such hinge?

[Gregovic]

This depends very much on how thick the rod you are using is and the tools you have at your disposal. If the rod is thick enough I'd go with a notch in one end, and a thinned bit on the other, then get a hinge pin, drill a hole in the notched end slightly larger than the hinge pin diameter and a hole in the thinned end slightly smaller (press fit), then press the pin into the center part through the notched bit so they are pinned together.

When riveting you can countersink the ends of the holes so the head of the rivet comes flush with the outside surface. Getting this to look good is tricky.

Last option is using a countersunk screw, countersink one end and then drill and tap the other end to receive the screw.

Like I said, it depends on the material (Also, stainless comes in a lot of variety. What works for 304 might not really be doable in 316L which is much trickier to work for instance) and on the tools and skill available.

[polished54]

I forgot to write what steel do I have, its 304 and I have both 5mm and 6mm diameter pieces. I would like to make the collar using the 5mm rod, and perhaps in the future make another with 4mm. The thinner the rod the more it would look like a jewelry (I hope so).
The two parts of the collar will be overlapping just like those I saw in the internet, so one part has a notch, while the other has something which goes into that notch, like you said. I don't have tools for riveting so the first idea you gave me would be the best. That would still require finishing the end, so it's more or less smoth with the surface of the rod, but fine. Thanks

Also you say that 316L is much harder to work with. That's not good as I wanted to use this kind of steel in the future once I succeed with the current 304 experiment.
I'll let you know how the project is going

[Gregovic]

I forgot to write what steel do I have, its 304 and I have both 5mm and 6mm diameter pieces. I would like to make the collar using the 5mm rod, and perhaps in the future make another with 4mm. The thinner the rod the more it would look like a jewelry (I hope so).
The two parts of the collar will be overlapping just like those I saw in the internet, so one part has a notch, while the other has something which goes into that notch, like you said. I don't have tools for riveting so the first idea you gave me would be the best. That would still require finishing the end, so it's more or less smoth with the surface of the rod, but fine. Thanks

Also you say that 316L is much harder to work with. That's not good as I wanted to use this kind of steel in the future once I succeed with the current 304 experiment.
I'll let you know how the project is going

Do you really need the increased corrosion resistance of the added molybdenum of 316 grade though? I assume you're not really going to be exposing it to that many aggressive materials . It kind of depends on what kinds of tools you are working with when you are doing it. When I say harder to work it's mostly when doing machining operations like milling or lathe work where this comes into play. The added molybdenum makes for a much tougher material, meaning it's harder on machining tools. It's nowhere into Titanium ranges of difficult though. So don't let that comment discourage you.

If you are going to be welding it, I do advise to use L grades (304L or 316L) as the lower carbon content makes creating good welds that much easier. Welding higher carbon stuff can be done, but it's something to be left to the craftsmen instead of us mere mortals.

One last comment before you take these experiments further, keep in mind that AISI 3xx series steels contain both nickel and chrome, both of which CAN trigger allergic reactions in humans, so keep that in mind and maybe test if you are allergic to it before you end up with an itchy red ring of annoyance etched into your skin for weeks . It probably won't kill you in any case, but it'd be a shame of all the work. (of relevance here:http://www.bssa.org.uk/topics.php?article=130. Both 304 and 316 grade steel should be fine, but it's good to keep in mind if you do have a nickel allergy)

If all you have to work with are hand tools, you could make the hinge pin out of simple music wire (easily available in a range of sizes, quite tough material and finished to quite close tolerances) and get a reamer to get a press fit to the size of wire you choose. Have fun

[TheGentleman]

Way back when..... I heard about a technique where the hole was drilled a fraction SMALLER than the pin to be used. You then cooled the pin (think liquid nitrogen cool), and heated the hole area. The heat expands the hole, the cold shrinks the pin. Once you drop the pin in place and the temperatures equalize, the pin is actually trying to be larger than the hole it's in. If you drilled the second hole larger than the pin, that should allow you to use the joint as a hinge. If this technique really works, and you can protect a person from the temperature extremes, it would make a good permanent fastening as well. Once the pin is in the hole, it's almost impossible to heat the hole while cooling the pin to release it.

Please tell me this wasn't one of my more realistic, but false dreams.

[Gregovic]

Not really that unrealistic. When you are talking about a small pin you don't really even need to crimp the pin into the hole using temperature difference, a good clamp or vice combined with some carefully chosen tolerances will suffice. It will never be truly unremovable as the pin can be driven out with some extra tooling but making something truly impossible to remove is completely impossible. Give me a way of fastening and as an engineer I'll come up with a way to remove it again. Some of it might be uncomfortable for the person who is wearing the item, but none of it should result in permanent damage to the wearer (Though most of the time it'll destroy whatever item is getting removed)

Using heat, cooling or both to press fit a part is a technique used quite often if using force on the item is undesirable or simply impossible at the point of installation, so something that'll be quite well fixed in place once temperatures equalise can be dropped into place easy when it is warmed up. This is most often done with (ball) bearings, where using force if very undesirable as it might affect the lifetime of the bearing (even the slightest deformation or cracking on the balls or races can seriously influence bearing lifetime). See for a demo with some entertaining comment: https://youtu.be/LVODJm05plw (warning: some semi-foul language)

[polished54]

Thanks for your advices. It seems I have the whole concept ready in my mind. This cooling method obviously would work but I'll try something simpler first, and just force the pin into the hole. If that fail I'll be thinking about more clever way. Also I'll do experiment on aluminum rods that I also have left to see if all those concept work.

So you tell me that 304 steel is fine? So why they all make their toys with 316L? All the chastity cages, collars and other things claim to be made of 316L, I also must have such steel! Ok, just kidding Maybe you're right, maybe it's an overkill.
I've read that most collars are made of 8mm rod, so mine 5mm would be already lighter and smaller, maybe I won't need to try making 4mm collar. As far as I' concerned I'm not allergic to metal, hovewer it's not me who would wear the it

[Gregovic]

Thanks for your advices. It seems I have the whole concept ready in my mind. This cooling method obviously would work but I'll try something simpler first, and just force the pin into the hole. If that fail I'll be thinking about more clever way. Also I'll do experiment on aluminum rods that I also have left to see if all those concept work.

So you tell me that 304 steel is fine? So why they all make their toys with 316L? All the chastity cages, collars and other things claim to be made of 316L, I also must have such steel! Ok, just kidding Maybe you're right, maybe it's an overkill.
I've read that most collars are made of 8mm rod, so mine 5mm would be already lighter and smaller, maybe I won't need to try making 4mm collar. As far as I' concerned I'm not allergic to metal, hovewer it's not me who would wear the it

316L has become sort of the defacto standard because people assume that because it's "higher grade" it must be better. The reputation on 304 has been tarnished a bit by cheap crap from china being labelled as 304 stainless when it didn't really qualify for the moniker. Combined with the fact 316L has developed a reputation of being "surgical steel" (Nevermind AISI 304 is perfectly legit to be used for surgical implements, just not for long term implantation) so people assumed it would be the only safe material for body contact.

Depending on the object 316's higher yield strength and hardness might be better, for most stainless steel objects 304 is perfectly acceptable. As long as it actually meets AISI 304 standards, unlike a lot of the China 304 "stainless". Its a call you have to make yourself.

[polished54]

Good to know, thanks I have relatively easy access to 304 steel, where they sell low quantities. The other company I asked about 316L told me that I can get a discount if I buy 3 tonnes
Also just out of curiosity I calculated what would happen to a 3mm hinge pin that I want to use when cooled with liquid nitrogen. Unfortunately according to wikipedia's coefficient for thermal expansion of steel, it would contract only by 0.008mm. Not very useful. I'll drill one hole with 3mm, the other with 2.9mm and see if that hold together. If not I can go down to 2.8 or even 2.7.

[Sir Cumference]

Don't drill the hole all the way through, drop in the pin with a bit of glue and file it flush.

The only way to remove it, will be by driling it out.

[Blacky]

Just out of curiosity: How will you do the bending?

[polished54]

Since I make a 12cm diameter collar out of a 6mm steel rod, it should be bendable in hands around some round wooden block or pipe or some other shape. I tried it before with slightly bigger diameter and it worked.

The only problem would be making that notch in the rod, as routing steel with <2mm wide router bit can be tricky. I tried cutting the rod with a saw and then filing the sides. Perhaps with some precise template it can be done consistently. I don't need much overlap, just 6mm of space would do fine, as I have bought 2.5mm hex screws, and the hinge pin would be 3mm diameter.

I won't use glue, just force-push the pin, but still file it smooth with the surface. That would make enough for the hinge. Or did you mean a way to permanently lock it on someone?

And I made a 'collar' before, out of flat aluminum piece by simply bending it 16 times 22.5 degrees. It does not have any hinge, to wear it you have to spread the ends and slip it on your neck. Then you press the ends and lock with a padlock. It does not look great, quite the opposite, but serves the purpose

[Sir Cumference]

A push fit will probably work perfectly well too.

As soon as you can't push the pin through, it will be very hard to remove, and even the tiniest friction will hold it.
But working the hinge may make the pin crawl out if it is not held in place.
Think about the pins in door hinges. They will crawl out, even when being so tight, that you needed a hammer to insert them.

(I was thinking "lock")

[Gregovic]

A push fit will probably work perfectly well too.

As soon as you can't push the pin through, it will be very hard to remove, and even the tiniest friction will hold it.
But working the hinge may make the pin crawl out if it is not held in place.
Think about the pins in door hinges. They will crawl out, even when being so tight, that you needed a hammer to insert them.

(I was thinking "lock")

If all you have is handtools getting a pushfit and using some glue (loctite or somesuch) is perfectly legitimate to prevent crawl. And on a small pin, if you use the permanent stuff it's NOT coming out