Whats the nornal way to connect up 1/8" OD copper steam pipes
(actually compressed air in this case)? I have made a union and nut,
but I am not sure whether I should solder a ring onto the pipe,
attempt a compression fitting, or make a nipple into which the 1/8"
pipe can be soldered outside the nut. I am thinking the soldered brass
ring, turned true, might be tidiest.
It is usual to silver solder the nipple/olive onto the copper pipe (after
putting the nut on first) Both the 'arrow' shaped nipples of the type sold
by model suppliers and very small olive shapes work in my experience. You
just have to be careful how much SS you use with the latter.
Presumably these arrow-shaped nipples are 1/8" ID and slip over the
pipe. This will increase the hole size required in the union nut and
decrease the shoulder for the union nut to work on. Also I am not sure
it will look half as tidy to have an exposed soldered joint outside
the union nut.
I am avoiding buying items like this as the main reason I am making
this is to improve my skills with the lathe - and everything I make I
learn something more.
For compressed air, soft solder should be satisfactory and the solder
should be inside the nipple and thus, all that ought to be visible will
be a tiny fillet between the top of the nipple and the pipe. If you are
unsure of your skills with a soldering iron, a small tub of solder paste
is not cheap but in the quantities that you can expect to be using it
will probably last a life-time.
Assuming that the required nut is 1/4" x 40 t.p.i it may be worth
spending a couple of pounds on a small pack of commercial nipples and
nuts. Attempting to replicate both nut and nipple may be much more
difficult than you expect and hence be another new skill acquired.
In this instance it doesn't have to be to scale, but for my next
project it will, so if you can give me a pointer to something that
looks like full scale practice that would be excellent. It will be
semi-permanent, the other end of the pipe will have a connector for an
air-hose at the edge of the plinth - which will also have a union. I
have also to discover how much bend this pipe will take before it
kinks - I dare say a search on this newgroup will reveal something on
Are you maybe going to suggest using a tiny silicone o-ring in place
of an olive ? Do they come that small ?
First, anneal the region that you intend to bend. Heat to red heat,
allow to cool (cooling rate does not seem to matter) then re-polish with
fine steel wool.
There are relatively cheap bending tools on the market. But for really
small radius bends that need to follow an accurate line you may well
find that you need to make your own bending jig(s).
Yes. O-ring rulez! :-)
+-------------+ +--+ | |
| | O | | | | <- Nut (bored through)
+-------------+ | | +-----+
--SSS+ +----+SS+------------------- <-Tube
---- . --- . --- C.L.
Not to scale. :-))
VVV is a thread, of course the mating part has one too.
O is the O-ring (bigger, just fits over the tube)
SSS is silver solder.
HHH is where the hex is.
Made something like this with a tube OD of 6mm.
With a 6mm tube, the O-ring might be a 6 x 1. So the sleeve soldered over
the left tube will have an OD of 8mm. The bored nut will have an OD of
10mm. Thread will be M8 x 0.5.
It is wrong if the OD of the O-ring has contact with the thread. It wouldn't
If you follow the tube coming up near the flywheel and going horizontally to
the left and then making a 180° bend into a valve. The joint valve/tube is
of that type. Has to hold 10 bar.
Thanks for your advice, but I am curious to know what is 'classical'
full scale practice, and could I follow it ? I think its covered in
various ancient ME magazines I can spot in the index, but I don't have
Smaller pipes tend to have a coned sleeve and larger ones a ring, though
the practice varied from one railway to another. Remember that a most of
the larger pipes would be flanged, except in the cab, where they mostly
were not, except on the manifold where they often were. Don't ask me to
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