TromboneChat

How is it done? Also, how is the tube made? There’s no threads for tube bending but i am really fascinated by it.

Perhaps no thread on TromboneChat – but remember - Google is your friend

You can find out how to do practically anything on YouTube!

Tubes used to be (and sometimes still are) formed from a flat sheet of brass that is rolled into a tube, and seamed with hard solder where the long faces meet (can be overlapping or end-to-end depending on the purpose of the tube), then some extra work needs to be done to flatten the seam and make the tube properly round before drawing. Now most tubes are typically made from extruded (and seamless) industrial tubing.

In either case you then anneal the tube, then draw it onto a mandrel of the wanted inner diameter and through a die of the right size, which pushes the brass onto the mandrel and gives it the correct outer diameter and wall thickness. The overall diameter and wall thickness reduction mean the tube becomes stretches and becomes longer (the material has to go somewhere).

For bending, you anneal again (the drawing will have made the brass hard again), then pour into the tube a material that is both flexible but wants to keep its shape. That can be pitch, some water and chemicals solution that you then need to freeze, or a molten metal/alloy that is flexible at room temp, like lead or cerrobend. That material will keep an outward pressure inside the tube and prevent it from caving in and crumbling, and will keep wrinkling to a minimum. You then place the tube against the form of the curve you want and bend the tube onto that form (in a proper large production, jigs are used for ease and consistency). With seamed tubing, you'd place the seam so it's to the side, not facing into the bend (that side will be compressed and the seam might crumple and get punctured) or away from it (that will be stretched and the seam might split open). You then heat the tube to soften/melt the stuff you put inside it, pour it out and clean the inside of the tube. Often the inside face of the bend will have some wrinkles from the bending which you then need to gently hammer out, and often run balls inside the tube to make sure the inside diameter is even (big industrial productions might have a machine where the tube is encased into a form and fluid pushed into it at high pressure to expand the tubing and take any wrinkle out).

You may get some interesting information here:

https://video.search.yahoo.com/search/v ... tion=click

what he said, not this:
https://www.homedepot.com/b/Electrical- ... 5yc1vZbmcy

https://www.homedepot.com/p/Klein-Tools ... /100660166

Go talk to the Tuba guys for tube manufacture and bending. You'll find a lot more there. Frankentuba group on FB, TubeNet, and there are some other places they discuss this. You can even get some pre-filled leadpipes for tuba from Allied that you can bend to fit.

It is fascinating and fun. Never want to do it again.

Cheers,
Andy