OK, now I know what I'm looking for I have a question about strength.
I am in the process of making a pair of manacles for a friend for a hallowe= en costume. The manacles are meant to look steampunk and are of a steamed c= urved hardwood with brass fittings. The hinge will be brass and I plan on r= eplacing the hinge pin with a d-ring. This is for a small length of brass c= hain (3-4 links). Despite these being a costume piece, I am more then sure = that they will see use and I am more then sure that some bright spark will = try to "break free" by tugging on the links. You know how that goes, I'm su= re you've seen that in the movies! Anyway, to save face I have decided to s= pot weld shut the gap in the d-links so it doesn't separate under tension.
I don't quite see how the D-ring will replace a pin, and don't see the wisdom of making the manacles strong, but all that aside, is the D-ring brass, or is it steel? And is the D-ring junction in the middle of the flat side of the ring?
For a ring, brazing might work better, for either steel or brass, because most little spot welders can only weld together bits of metal sandwiched between the electrodes, with current from electrodes flowing through the sandwich. Most heating occurs at the junction between the two sheets, because that junction typically has much higher resistance than other points in the circuit.
If you try to spot weld a D across the junction (perpendicular to the plane of the D) with nothing pushing the ends together, it won't work particularly well. It might make a connection stronger than most people can pull apart, but probably wouldn't resist being bent apart by hand (if someone can bend the ring). There are commercial welders for D-rings, that push the ends together and run the current axially through the junction, in the plane of the D, making a connection as strong or stronger than the wire of the ring.
No. Spot Welding won't work without spending a few grand on special tooling, and I doubt you want to do that.
When they manufacture welded chains for sale they have to use special cupped jaws on a industrial-duty spot welder to clamp the two ends together and transfer the power to the chain link ring on the gap side. And it takes a LOT of power to weld chain links, because part of the power is wasted going the other way around in the chain link rather than across the gap. They usually use a 600-Amp class industrial arc welder for welding chain links, not your little 100-Amp hand-held spot welder - it's made for thin sheet-metal, period.
You'll have to Braze the links and D-rings shut. Oxy-Acetylene torch, brazing rod, brazing flux. You can close up brass chain and make it a lot stronger, and look hand-made.
Silver Braze is a lot easier to work with, but it's more expensive per stick (though you don't use that much) and the color is going to be slightly different from the brass chain. But that's the stuff they use for connecting air-conditioning refrigerant lines.
The D-Rings might be Brass Plated Steel wire, don't be surprised. Check with a magnet. It'll braze the same - but the steel in the core won't melt on you, it'll just fuse the joint. The entire brass chain link will melt on you if you get it too hot.
I'd like to see the design where you can replace the hinge pin and braze the ends shut, though - you need to spread the D-ring and then bend it closed into the hinge to replace the pin - then the ends will be hidden inside.
You would have to bend the tabs of the hinge leaves OVER the brazed-shut D-Ring to make that work.
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You can buy a small Oxy-Acetylene Welding and Brazing Torch Kit for a couple hundred at Lowe's, Home Depot, Harbor Freight, Northern Tool, etc. and you can keep and use it for many little jobs around the house and garage for many decades. Tank exchanges (empty for full) will be $20 to $40 depending on local market rates.
The little "Porta-Tote" style torches with the plastic bottle carrier,
20 cubic foot size Oxygen and 10 cubic foot 'MC' size Acetylene are between $200 and $300, shop around. The small cylinders will be enough for this project, but a little *too* small for working on cars and home repairs.
Air Conditioning guys buy the Porta-Torch rigs solely because they can be hauled up on the roof or under a house easily... If you go this route, consider buying a second set of cylinders so you have more gas when {not if...} they run dry on you in the middle of a job. About $200 for a filled set.
For doing bigger things like car body repairs and gate hinges, you want to step up to the 50CF Oxygen and 25CF 'B' Acetylene size welding rig - a little more investment up front (about $400 for the torch, 25' hose, regulators with a cart and a set of cylinders, and about $220 for a filled set of spare bottles) but they are big enough to actually DO something.
The main plan was to make my own Brass d-ring. Instead of having the split inside the hinge, it would have been at one end of the flat section just before it curves round into the D shape. That's why I was concerned about it separating under tension.
But looking at the options I think I might have to try a D ring with two Ds. Sort of like a keyring!!
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