Hm interesting.
I'd like to hear from someone who has done it as well.

If I were working on it and the material was thin enough. I would make two bolt like mandrels the larger the same pitch and the od of the smaller plus 2x thickness of the material, and chase the threads in.
If you have the engine lathe to cut the mandrel threads, it could also be used to chuck up the mandrel and chase the threads down with a roller "dull cutter".

Gene Olson
Sculptor
Elk River, MN

I have done this somewhat satisfactorily by cutting a nut in half (of the thread needed) and then pressing the halves of the nut over a bolt covered with a blank metal pipe shape. This necessitates hand work to finish the threads. I used a pipe die to thread a piece for the male side on the container. Of course you don't get the "rounded" style of threads.

The wood threading tap and dies are made of hard wood and have the "rounded" style. I wonder if the metal was soft enough if they would work?

A tool machining supply company might have metal cutting tap and dies that will do the "rounded" style thread.

scrollerbear

Threaded neck and cap. I think I'd start with wrapping some half round wire around a suitable sized mandrel. Let's say 1" tall. I'm going to do this on a press. Using the concept that when I smash a piece of rubber It gets thin under the press, that material moves to the side. It takes the vertical pressure and makes the pressure go horizontal. You will need two silver cylinders that telescope each other and will both fit over your mandrel. seamless is best. Neoprene instead of rubber. I'll have to make a tube of it about 1" thicker than the cylinders. put a release agent between the telescoping, soon to be parts. could be plastic wrap. insert the mandrel. put the cylinder of neoprene over that. put a tight fitting pipe section over the package. use your socket set to find a cylinder that fits between the pipe and your hollow about midway. press it. should produce two threaded to each other cylinders. That's the concept. Very doable very quick. Anneal before pressing. hydraulic necking. On your form is just a matter of setup on the press. Brad

here's an idiea(hope i can expain it clear anough in english)

someone at my school made round box with a screw top lid once.

he mad a drawing iron(again dont no if its the right word. what you use to draw thread)shaped like this

[| |] [| |]
---------------------
--------vvvv---------
| | | |
------[]----[]-------
---------------------
[| |] [| |]

ok not a very clear bleu print. it basicly two rectangular steal bloks with two heavy bolts at the sides. in the midle you file the profile of a screw(the vvvv). when you take a strip of silver r whatever soft metal you are using you can draw it in between the bloks(fixed in a vice). every pass you tighten the bolts a bit more.

in the end youve got a strip of silver with the groover you want. you can bassicly use this principle to make thread into whatever shape you want
now you can roll this around a mandrel(mandrel is jus a round rod at the diameter you want wright?)
and saw it off. now bend your tube to be slightly so that the groves don't line up straight but in the spiral of a screw. solder it. hammer it around a mandrel with a rubber hammer and carfuly work your seam with files without damaging the grooves.
now just repeat the same proces with the lid only whit theg grooves on the inside(be careful not to damage the grooves with the mandrel.
now this princyple doesn't work for very well on small diameter tubes but the i think i could do it on your example pic(thoug the size doesn't show)
what was youre diameter again?

ther are some details about the drawing iron that I find kind a hard to explain. if youre realy interested in this idea I could post a pic. I hope you catched my drift and understand what I ment.

goodnight, ambition

I've made threaded pieces by wrapping two wires around a rod, "unscrewing" them, solder one around the rod and the other to the inside of a tube. This was for screw clasps on wide bracelets.  Oughta work fine here.

I suppose I'd probably try to roll the threads on the lathe using a radius wheel and progressively harder pressure until I got the right depth. That would get the male threads, now what about the female? Perhaps chuck up the male threads (hard from the last rolling pass) and spin a sleeve onto them with some parchment between the two for clearance. Burn out the parchment and unscrew the femal from the male. Might work, just brainstorming what I'd try if I was determined to make rounded threads in tubing.

What I would probably do in practice, is to make three pieces of nesting tubing and then cut a spiral slot in the middle one to engage a stud or two on smallest one. Solder the middle one inside the largest one and you have the female. The smallest one with the stud(s) becomes the neck of the bottle. A slow ramp on the slot should give you a tight seal on a gasket with about a quarter turn, I'd think. More screwing around.

This was a really great question, with a bunch of good possible answers!

In case anyone wants it - there is a tutorial available for 4 bucks from Lap Jrnl that shows the method referenced of using a coil of wire, spacing the coils, cut in half, solder one on outside of a tube, the ohter on the inside - presto - screw.

Here is the link:
http://www.lapidaryjournal.com/jj/1299jj.cfm

HTH!

~Janice