How to cut a thread on small pipe fittings 1/2 inch in length ?

John : most of my model engineering supplies and tools come from the UK with a few from the US.

Indeed. Until I moved back to the UK from Canada last year, I found it was often cheaper to buy stuff in the UK, even after allowing for tax, duty and carriage. That was true even for Chinese and Indian tools. I suspected this was due to protectionist import duties (into N America) and the fact that locally made tools ("Made in USA" stickers everywhere) were often of indifferent quality but still damned expensive (those stickers must be expensive), thus providing a high floor price for competing (imported) low end products.

I'm aware of the existence of pipe threading heads, manual or powered but for either serial production or workshop one-offs, neither these nor split die are going to be much use to you when it comes to making a double-ended tapered pipe thread.

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Jason: A variation on your theme, if I may ...

Brian: Although you do not yet have a lathe; I believe that you do have a drilling machine [if not, then please ignore what follows]

Instead of a plate; tap a piece of suitable tube, long enough to fit securely in the drill chuck [this may require some initiative, such as silver-soldering a sleeve over a shorter piece] then proceed as Jason suggests.

With the drill unplugged: lay the die-stock on the drill-table and use the machine as a "pillar tool".

I would recommend hand-holding the die-stock, rather than clamping it, because that way it can "float" and accommodate any error of concentricity in the workholding.

MichaelG.

Can't agree Muzzer. Brian already makes longer one and has a die so the problem is holding an end that has been threaded while he does the other end on rather short ones..

If he taps a hole in something to take the threaded end he has done he can handle shorter lengths. It will probably make it easier to do longer ones as well. He may have to buy an NPT tap or may already have one. Personally to be sure of being able to easily remove the part I would drill right through what ever he chooses to tap and open out most of it to a size to suite some suitable screw and tap that section for this screw, the rest for the part. This way he can lightly screw the part he is making in it's end and then hold it firmly firmly in place with the screw - sort of lock screw arrangement using the same principle as lock nuts.

Michael touches on an interesting point. I sometimes use a drill chuck to hold things for hand work. He might find it will bruise the thread that he has done when it's tightened sufficiently to hold the part while the other end has the die run down it. A bit of suitable rubber tube or a couple of wraps with masking tape might help with that.

As to how THEY make them. A cnc machine could make them in one go. If they used capstan type techniques, one threaded end while on the tube, part of and place in a fixture and thread the other end. The fixture might be a collet or something along the lines of what I described above or earlier. If they make millions it can be very surprising how well parts can be orientated and placed in machines automatically. In that case one machine would thread one end and part it off, then on to another machine to thread the other end. All sorts of things are possible even automatic transfer of the part from one machining operation to another on the same or another machine. I get the impression that some brass fittings are initially cast so I'd guess the industry has this sort of thing well sorted out using special purpose machinery some of which might have more than one spindle.

John

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