GS User Question - Fasten a Square Tube to a Round Tube

Tough, no idea what loads are involved. Contact between dissimilar metals?

Weld plates with tapped holes or threaded studs into the ends of the aluminum and weld matching studs or drill matching tapped holes in the steel pipe.

Then watch the steel rot away.

As observed, no info about loading.

This item will accomplish the stated objective:

This is a rod to latch connector for a vertical rod exit device. The smooth end is 5/16" round, and the thread is 5/16-18. Round end slides into the rod, held in place with a spring pin.

As an aside, why not invite the questioner to join the forum? Isn't that the idea?

Machine undersized square holes in the steel tube, and slide the Al spindles through the steel tube so they are captured on both sides by the steel tube.

Now, freeze the Al tubes, heat the steel tube, assemble and allow to return to room temperature.

If you get the thermal expansion figures right, it should capture the Al spindles.

The sequence above isn't very clear.

Machine holes to proper size. Heat steel tube, freeze Al spindles. Assemble, let return to room temperature. If the spindles can protrude equally from both sides of the steel tubes, that's even better.

How about a sketch? Is this to be a 'T' or a cross configuration? How long are the legs? And how much load is involved?

http://www.esabna.com/us/en/education/knowledge/qa/Can-I-Weld-Aluminum-to-Steel.cfm

Square expansion fitting.

http://www.rosscastors.co.uk/square-expanding-tube-adaptor-to-fit-square-tubing-with-internal-diameter-from-29-32mm.html

1) We don't know if the inside of the alum spindle is square, round, solid...

2) With this fitting it won't be possible to scribe fit the spindle to the round pipe.

3) We still don't know (and probably never will) if any of this matters.

True...and since the question was lifted from GS, we'll never get any answers from the person asking the question.

They should just refer GS people that have questions, directly over here. Lyn can yell at them, and we can all call it a day.

Send 'em all to me. I'll pass the survivors along to the rest of you.

It'll thin the herd.

Look, quite wasting time here and go research my AC thread. It will end up like the garage painting fiasco, but what else do you have to do?