Am hoping to do the following. I want to put a venturi in an aluminium tube. Venturi ID needs to be small, of order 2.4 mm.

1) Get an aluminium tube with OD >= 30 mm.
2) Put it on a lathe and spin a short section (about 30 mm long) down to make the venturi. I can use a wood former if that helps.
3) Machine cut extra features on the tube, such as a screw thread on the inside.
4) Harden aluminium.

Can that be done? It’s like “aluminium spinning” but starts with a tube instead of a disk.
What grade of aluminium tube, if any, starts very soft but can be hardened?

mollwollfumble said:

Am hoping to do the following. I want to put a venturi in an aluminium tube. Venturi ID needs to be small, of order 2.4 mm.

1) Get an aluminium tube with OD >= 30 mm.
2) Put it on a lathe and spin a short section (about 30 mm long) down to make the venturi. I can use a wood former if that helps.
3) Machine cut extra features on the tube, such as a screw thread on the inside.
4) Harden aluminium.

Can that be done? It’s like “aluminium spinning” but starts with a tube instead of a disk.
What grade of aluminium tube, if any, starts very soft but can be hardened?

Mr Speedy (used to be a fitter/machinist) says:

- 6000 grade onward is weld-able grade

- to use bar, not tube, as you won’t be able to hold tube in a lathe

- aluminium cannot be hardened, but can be anodised, however anodising will make it brittle.

> you won’t be able to hold tube in a lathe

D@#n. Why not?

mollwollfumble said:

> you won’t be able to hold tube in a lathe

D@#n. Why not?

It would crush

mollwollfumble said:

> you won’t be able to hold tube in a lathe

D@#n. Why not?

you can,but you willneed a bar inside it toput it on a lathe

You may be able to use a short length of bar that fits neatly into the end of the tube to stop the chuck from crushing the tube.

stumpy_seahorse said:

mollwollfumble said:

> you won’t be able to hold tube in a lathe

D@#n. Why not?

you can,but you willneed a bar inside it toput it on a lathe

Mr S – Why would you stuff around with doing this when you can simply use a bar of aluminium and “part it off”?

Speedy said:

stumpy_seahorse said:

mollwollfumble said:

> you won’t be able to hold tube in a lathe

D@#n. Why not?

you can,but you willneed a bar inside it toput it on a lathe

Mr S – Why would you stuff around with doing this when you can simply use a bar of aluminium and “part it off”?

the fact that moll is attempting to make a venturi for a start.

tube will make that part much easier

venturi for a rocket engine? get a lump of graphite. personally, it would be easier to turn a venturi rather than spinning one.

mollwollfumble said:

I want to put a venturi in an aluminium tube.

Why?

> Mr S – Why would you stuff around with doing this when you can simply use a bar of aluminium and “part it off”?

I’m actually paying someone to do that right now. But pushing a tube in would give a lighter-weight result, and be easier than making special tools to shape the inside of a venturi.

> you can,but you will need a bar inside it to put it on a lathe

It would be nice if a wooden bar inside would suffice.

> tube will make the venturi much easier

Yes.

> venturi for a rocket engine? get a lump of graphite. personally, it would be easier to turn a venturi rather than spinning one.

Yes, venturi for a rocket engine. Silly me, I already have a lump of graphite that I bought specifically for that purpose. I forgot all about it. Must dig it out ASAP.