Attention Craig Smith:  You said on Aug 17th that you are looking
for a rod diameter of 0.055", which is 1.397 mm.  I see Doug Baker's
note on the 19th, in which he thinks you will find the screw thread
is 1.5 mm diameter X 0.5 pitch.

I found some very fine threaded steel rod several years ago at a
model shop in Fayetteville, North Carolina.  I bought a handful in case
I needed some more later.  I believe they were used in model planes.

I just measured the rod diameter as 1.75 mm and the outer diameter
of the rolled thread as 2.0 mm with a metric dial vernier caliper.
The pitch on the threads is very fine; I rotated the rod twenty
revolutions per centimeter, or a pitch of 0.5 mm.  This rod has a
threaded length of 2.0 cm and an overall length over 40 cm.

These were the closest I could find to the vertical threaded brass
wire used in the bottom board action of a Kilgen organ windchest.

Best wishes,
Doug Dexheimer
Overland Park, Kansas