- Necessarily, the threads into the pistons need to be smaller diameter with any of these types of designs.
- Stainless steel stems (or nickel silver, or bronze) would be less fragile, but everyone makes them of brass - whether lacquered, silver plated, or nickel plated.
- Children today aren't encouraged to be careful, and nor are they punished when they are clumsy.
- Lot's of this type of valve stem (Yamaha, Jupiter, JP, Jinbao, Eastman, etc., etc...) break much more easily than old-style piston stems.
Two places to acquire JP valve stems are Allied Supply (USA) and JP (London, UK).
Yamaha stems (two different lengths - euphonium/marching baritone and tuba) are very similar.
Yamaha stems use an M4 x .75 thread.
I believe I've discovered that JP uses (simply) an SAE 8-32 thread.
If you have a Yamaha stem on hand (junk/missing parts plastic-guide tuba/baritone/euphonium) and are able to chase its metric thread to this SAE thread, you probably end up with a good-enough JP stem.
me...last night:
I got home from my Sunday gig (BADLY needing a long nap - having played an out-of-town concert Saturday night), found out that Mrs. bloke had done a Sunday morning school pick-up of five sousaphones...that they needed me to repair Sunday, so they could have them ALL back Monday morning (wtf?).
One was nothing more than a sousaphone valve stem (that school-aged child had rammed into a door frame)...
I did my regular trick with the screwdriver (pounding a slot into broken-off threads, and unscrewing them out of the valve).
I had some more (euphonium and tuba JP stems arriving TODAY/Monday (they arrived about 1:00 in the mail), but that band director wanted all that stuff at 9:30 A.M...so I silver brazed the threads back onto the rest of the stem, pickled the stem in acid (while still hot - to clean it) and then decided to re-tap the two bottom spirals of the threads (to avoid struggling to screw the stem back into the piston).
It was then that (already knowing the thread was different, but suspecting M4 x .70 - vs. .75) - instead - I tried the 8-32 die, and it chased the JP threads perfectly.
bloke "People re-sell Yamaha parts on eBay (as the only places to get those are California - which has become unresponsive - and Allied, so I'm toying with the idea of selling JP stems/guides/buttons and such on eBay...but the reason that I won't is because I don't like triffling with reselling parts, and never have."