In article ,
Allan Adler wrote:

The questions a
(1) How would one make a long metal pipe (e.g. a few feet) which is as thin
and as hollow as a syringe needle?
(2) And what if one wanted the pipe to follow some path other than straight?
Probably it is too thin to bend without closing it off, no matter how
carefully one tries to do it. Maybe one has to make miniature versions
of all of the standard plumbing fixtures and, to make sure the connections
are strong enough, one allows the outer diameters of the pipes to increase
where the threads are. So that feature of the pipe design would also have
to be included.

When I needed tiny pipe recently, I used a piece of refrigerator
cappilary fropm a junk refrigerator. Probably smaller ID than a syringe
but can be bent without closing.

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