hinge help

[zahc]

I'm building a welding fixture. I need to hinge together two rods (1/4 to 1/2 diameter) in such a way they are perfectly coaxial when straight, but they can be bent vs. one another, but not rotate vs. one another. A simple, in-line hinge, except it also needs to have adjustable tension so it can be locked in place. I see these on railings all the time but I don't know what they are called. Beach umbrellas have a similar joint. I will have to make my own buy I would rather buy. There must be such devices for holding test tube clamps or photography lighting gear I just don't know what to search for. McMaster has a hundred types of hinges but not these.

[Triphammer]

I've used these or made something like them for what I believe you're describing.


https://www.mcmaster.com/tie-rod-ends

[K Frame]

Try searching on these terms...

Lockable flexible elbow joint


You might also try surfing around here:

http://www.wagnercompanies.com/products-services/railing-systems-and-components/railing-components/connectors-for-pipe-and-tube/

[French G.]

Two pieces of round stock,  longitudinal hole bored to half the length to accommodate the rods, other half mill a flat down to centerline, bolthole in each, one side tapped, one side clearance, relieve the corners of the flat ends so there is room to rotate.

[Fly320s]

Something like this?

https://www.amazon.com/TechnologyLK-EZ-Rod-Hinge-Assembly-Rod/dp/B005Y2YCJO

[dogmush]

To meet the "perfectly coaxial" part I would probably do mostly what French suggested, with the addition that I would face the two ends of the rods so they were nice and perpendicular to the axis.  Then mill two flats half the diameter of the rod (+ a thou or so for clearance), drill and tap one, drill and countersink the other (if the diameter allows) for a cap head bolt, then radius the ends so it rotates.  If you only radius one side, it will index on the machined faces and give you a solid "perfectly coaxial" reference.  Tighten or loosen bolt for tension, or maybe throw a small Bellevue Washer in between.

[zahc]

Something like this?

https://www.amazon.com/TechnologyLK-EZ-Rod-Hinge-Assembly-Rod/dp/B005Y2YCJO

Exactly that. But for $30 each, and the wrong size, it looks like I will be making my own.

[Fly320s]

https://www.standoffsystems.com/product/ez-hinge-assembly/

Maybe a better price here.  Maybe you can get a free sample.

[dogmush]

If that bulbous part at the hinge is OK, then it's pretty easy.

1/4" Spherical Rod End: https://www.mscdirect.com/product/details/35397827

1/2" Rod Yoke.  https://www.mscdirect.com/product/details/82055096?fromRR=Y

Add bolt and nylok for tensioning

[zahc]

Ball joints and U-joints are right out. It's critical that the two rods can't rotate with respect to each other.

I will just make one. I just thought there would be a name for that sort of fitting.