A pal of mine is making a gadget and needs but a short length of square metal tubing that will accept a 5mm square drive. OD is relatively unimportant. This is to act as a drive coupling. Must be fairly sturdy, probably steel or stainless would be best.
Any ideas please where to find such material?
Thanks
Nick.
How short? Would an old clock-winding key do? I would expect a clock repairer to have a box of old keys, although most would be round with a square end.
Thanks Jeff,
excellent lateral thinking.
1 inch would do the job. I'm not sure a clock winding key would do as they are internally tapered. However a clockwork train winding key is internally parallel. Food for thought. I have a box of both types of windings keys.Many thanks indeed
Nick.
Sorry, thinking head not on. I don't know that clock winding keys are internally tapered. I do know that clock winding stems are square and tapered and that clockwork train type mechanisms winding stems are parallel.
I will ask a friend.
Many thanks
Nick.
If it is a short length, what is wrong with drilling a bit of material and filing or broaching the hole square?
An alternative would be the judicious application of a large hammer to the outside of a bit of 1/4" ID tube, using mandrels up the inside of the tube to give the shape. The first would obviously need the corners turned off to fit inside the tube, with subsequent mandrels each nearer the finished shape.
You can, of course, get drills that will drill square holes (with rounded corners) but that would be overkill unless he was planning a production run.
Colin Bignell
take round tube and squash it in a vice, twice?
Steel tube of this sort of size can be found in car rigid brake pipes.Its not beyond the wit of man to hammer or press it into the right shape.
However, for a drive coupling, one would probably mill or machine or file a lump to the right shape to fit into a round tube or over a rod.
Or turn down something like a cheap socket with a 5mm head if such exists.
Hope it works out. If the "squaring the circle" suggestions from the other replies don't work, another possibility - although more complicated - is to use circular tube with grub screws tapped in to grip opposite sides of the square.
Just noticed that radiator bleed keys are about 5mm square. Don't know if the 5mm goes down more than a few mm though...
Does the coupling *have* to be square for some reason?
MBQ
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