I'm having to fix a steel cable (1/8" dia) to a small metal ball (1/4") in order to hook the cable into a slot. This is a replacement part for a device I've been using, but due to overload the original factory-made connection went -- the cable progressively slipped out of the ball.
I had a local workshop make a replacement -- they stuck the cable through a brass ball, jammed a conical piece of steel into the center of the open end of the cable, and liberally bathed the whole thing in solder. Upon my first trial, the joint snapped with a loud pang when it wasn't even loaded with half of its intended strength (max force in normal use will be about 700lbs).
My question is: How is this done professionally? Of course I could just order the original replacement part, but with overseas shipping and all I'd like to save some time by having this made locally.
The design of the unit, regrettably, doesn't allow any other way of fixing the cable to the rest.
You should be able to easily find 1/4" steel cable with a rating of over 3 tons so annealing shouldn't become a major problem. However: Is this an application where someone could be injured by the end pulling out? If so I might suggest assembling the cable end into a wedge shape by brazing, with a central tiny wedge inside (or by bending the strands inwardly over themselfs) and quenching while it's still hot followed by a lighter heat to finish temper (a lot of technique needed here). Then match the cone shape by milling/filing out the ball and finish by running the cable through the ball and lightly soldering. Not too stupid sounding, I hope. Dennis in nca
Sounds like your local shop had started along the right track, but didn't quite get there.
Instead of a cone shaped wedge, make the hole through the ball a "cone" shape. Doesn't have to be perfect, but definitely the "small end" of the hole must be the "cable size", just large enough for the wire rope to pass through. In your case, 9/64" should do", and the large end as large as you can make it on a 1/4" ball. Nominally, these are 3 times the cable diameter, but you can't "do" that with what you have. The cone "finish" should not be smooth, in fact it should have a surface that is slightly roughened for the last step.
Insert the cable through this smaller hole, and then seize it with tape or wire to allow you to splay the end for three times the diameter.
Turn the end of each of the now separated lays back on itself, bent so that the ends will meet "inside" the wire rope. Bit of a bitch to do, but forms a "rosette".
Pull really hard on the cable, attempting to pull the whole bud back through the ball. It can not pull out, due to you have effectively "doubled" the diameter of the cable.
While it is under this tension, now you solder it in place. The solder, babbitt, lead, or what ever, (I've even used epoxy), doesn't need to "melt into" the cable as though you were tinning or brazing. It just has to flow around it, so don't heat the cable anymore than necessary. It doesn't take much heat to damage these now individual little wires. This "socketing" doesn't stop the cable from pulling through, but merely keeps it in place so that it can't go the "other" way and push free when the tension is released.
Done properly, the cable exiting the small end will be "whole" and still twisted in it's proper lay, and none of the "splay" will be visible at the small hole end. On the large end, you may find that the little "loops" are visible. On items where it matters, these MUST show in fact, so that you know it wasn't just like what your local shop did.
What is this a part of?? It is quite common for fittings such as you describe to be Nico pressed, but you need the proper equipment and expertise to do this. If it is possible to take the cable to a marine outfitter, they may be able to do provide what you need.
And using a safety factor of 5, you should be using 3/16" cable for a
Funny, I was just looking into this. Suggest you poke around the Web site
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and find their "catalog request" page where you can download their architectural hardware catalog as PDF. In there they explain in great detail all about small wire rope and it's end fittings.
It should have been swaged on using a roller die.
You can buy mechanical fittings that go on with regular hand tools. These are more expensive, but they develop 100% of the wire rope strength. Or, you can have McMaster-Carr make you up your assembly.
I owned and operated a machine shop next to the Denver airport and swaged cable as part of our services. You need a high impact swager and the right die for the part to be fitted to the cable. No solder nor welding is involved. It actually cold fuses the fitting to the cable end. Look for a shop doing aircraft repair or servicing.
thanks for all the suggestions. I put the shop back on track; all this now amounts to is a race between the shop and the $2 replacement part shipped from overseas.
solder is the wrong stuff. Spelter ( zinc ) is used to attoch fittings to cables, but if I recall correctly the US Navy does not permit using slings with fittings attached with Spelter to be used to handle explosives.
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