Hello MMD.  Readers of this journal will be getting weary of my harping
on about the brass upper units in these valves.  They will be relieved
to hear that my troubles are over, at least for now.

I think I've already mentioned here that in 1983 I was on sabbatical
leave in Denver, Colorado.  One evening I went to visit Dick Kroekel,
a fellow enthusiast, and at some stage I mentioned that I had recently
purchased a Steck upright Half Duo-Art.  He told me that he had some
parts salvaged from a junked player of this type.  They might be
useful if I ever wanted to convert my player to a full Duo-Art and
would I like them?  There was only one possible answer to that offer,
so I packed them up and mailed them home.

The parts have sat at the back of a cupboard until recently, when
I began to rebuild the Steck.  The major piece was an expression box,
but there were a few other bits too.  When I looked a couple of days
ago, I discovered that one of the other odd bits was a valve chest
identical to my troublesome one.  When I tried the brass units from
Dick's valve chest in mine, they fitted beautifully, neither too tight
nor too loose.  I hardly could believe my luck!  So I've avoided having
to hunt down an appropriate thread tap, which would not have been an
easy job here in Tasmania, about as far from the U.S. as one can get
(without being an astronaut).

However, I have, I believe, determined what the thread is on these
brass units.  It is UNEF 13/16-inch, with 20 threads per inch.
The table of threads quoted by Robbie in MMD 081019
  http://en.wikipedia.org/wiki/Unified_Thread_Standard 
does not include this size, but a table at the efunda.com web site
includes it as a secondary thread size:
  http://www.efunda.com/designstandards/screws/screwunef.cfm 

If anyone knows better, please let us all know.

John Phillips in Hobart, Tasmania