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I found a beautiful Conn 80J BBb at an estate sale. It plays well, except for the third valve stem which will no longer screw into the valve. The second valve stem will screw into the third stems female threads, so it seems like the third valve stem male threads are either a different size or stripped.

Anyone have advice on:
1. Interchangeable valve stems? Brands that may exchange well with older Conn horns
2. Anything else I should think about before getting a new one made?

Thanks!

Allied Supply in Wisconsin has some little small shop jobbers around them that make some parts that are no longer made.

It's pretty obvious that sometime in the past they had a whole bunch of stems made up that fit 14k/36k/38k/10j/etc. (all the same size) made up by someone.

Maybe the first thing to do is to see if your first and second stems fit your third valve. And - if those are loose in the #3 piston, it's the female threads in the third piston that are faulty.
If they do fit, maybe it's worth trying one of those Allied stems.

Can you Helicoil a valve? Might be a better plan that would allow the use of the original stem, since it sounds like the threads on it are OK . . .

You want to contact Dan Oberloh in Seattle. He can fabricate any parts needed.

The viola burn pit, adjacent to his new shop is coming along nicely.

If someone nearby has an old 14K/36K (Elkhart) sousaphone, and one of those stems fits your piston(s),
here's the Allied Supply part #...

C-64195-1

They're quite reasonably priced, but you need to catch your repair shop ordering from them, because Allied has a $50 minimum order policy (and only from shops, no orders accepted from laymen).




Here's someone retailing them on eBay.
The price - ok: "in my view" - is "convenience store" pricing...but (yeah) they're charging for having to "mess with" selling ONE freakin' valve stem.


https://www.ebay.com/itm/274430407357

Are these valve stems rare or unusual? Would it be worthwhile to make a couple dozen or 100?

.

... I guess there's no interest in seeing if a 14K/36K sousaphone's stem fits this piston, and then asking a repair guy to add the Allied replica to their next order ($6 dealer cost) and buying from them for $12 or something... or buying the $18 one off of eBay that I linked.

MiBrassFS wrote: Sat Oct 18, 2025 6:31 am

tadawson wrote: Thu Oct 16, 2025 3:54 pm Can you Helicoil a valve? Might be a better plan that would allow the use of the original stem, since it sounds like the threads on it are OK . . .

People plug, drill, and tap rather than helicoil.

Seems kinda like the same thing, just the 'coil is screw in, and no drilling or tapping, and the plug ?? Friction? Solder? Seems like the coil might have less chance of deforming the valve, and there is very little load on it as well, so "strongest" would seem to be a non-factor.

.

It depends on how well the top plate is silver soldered into the piston tube and how thick it is.

One would never want to do this with one of those expensive Japanese brand marching instrument nickel-plated pistons, because those pistons are completely lead soldered together.

Again, didn't I read that the stem on this particular tuba is the one that the owner suspects has the worn threads, and not the piston?

Not sure . . . mainly just speculating, since a helicoil isn't terribly expensive, and doesn't require heat or pressure, so just wondering if they were used. Seems like it would be pretty low impact on the valve . . .

(I won't even begin to imagine how that thread gets stripped, since there should be almost zero load on it . . . .)

tadawson wrote: Mon Oct 20, 2025 8:17 pm
(I won't even begin to imagine how that thread gets stripped, since there should be almost zero load on it . . . .)

As a certified brass instrument technician and a member of

SEBT
(stick 'em back together)

Third valve stems get caught in doorways by young scholars.
Brass is soft, and the threads get flattened down so that either the stem threads or the piston threads or both get warbled out from being bent and straightened back dozens of times over the years.

It's The Science.

AKA abuse . . . (by any other name).

I'm still a bit surprised that the cap doesn't take the brunt of that, but then again, in 6 or so years of playing a Sousaphone "way back then" I don't think I even so much as scuffed it, so not really well versed in how to break them . . .

tadawson wrote: Tue Oct 21, 2025 11:39 am AKA abuse . . . (by any other name).

I'm still a bit surprised that the cap doesn't take the brunt of that, but then again, in 6 or so years of playing a Sousaphone "way back then" I don't think I even so much as scuffed it, so not really well versed in how to break them . . .

The top cap stem opening is almost always considerably larger than the stem diameter.

Once the threads are loosey-goosey, stop-gap strategies are useless, because of the constant movement/vibration...Even lead-soldering only lasts (typically) a year or so. The tightest-fitting stem-to-piston threads - typically are European and high-end Chinese. Some are so tight that they are very difficult to unscrew without bunging up the stem (or - if someone has a particularly strong grip) mucking up the piston's cylindrical shape.

bloke wrote: Tue Oct 21, 2025 12:59 pm

tadawson wrote: Tue Oct 21, 2025 11:39 am AKA abuse . . . (by any other name).

I'm still a bit surprised that the cap doesn't take the brunt of that, but then again, in 6 or so years of playing a Sousaphone "way back then" I don't think I even so much as scuffed it, so not really well versed in how to break them . . .

The top cap stem opening is almost always considerably larger than the stem diameter.

Once the threads are loosey-goosey, stop-gap strategies are useless, because of the constant movement/vibration...Even lead-soldering only lasts (typically) a year or so. The tightest-fitting stem-to-piston threads - typically are European and high-end Chinese. Some are so tight that they are very difficult to unscrew without bunging up the stem (or - if someone has a particularly strong grip) mucking up the piston's cylindrical shape.

Not to beat this to death, but again pointing to a helicoil as a better solution . . . they don't get loose (as you indicated that solder does), and I don't imagine that valves would tolerate brazing . . . or much of any higher temp process.

Aren't those things offered in only a few standard threads though?

I guess some of the stems are in fairly standard threads but some of them are sort of oddball and semi-proprietary.

I keep going back to what I think I read earlier which is that stems number one and number two screw in tightly too piston number three, which would indicate that the stem for number three is worn and not the female threads on number three piston itself.

Also, it still appears as I must have ghost posted about being able to buy those stems for vintage Conn pistons at a reasonable price.
It's as if I didn't post it at all, seemingly.

I dunno . . . unless someone went so far as to invent a bastard thread that isn't part of any standard, it looks to me like most anything from #1 (2mm metric) coarse or fine on up is covered . . . .https://www.stanleyengineeredfastening. ... _rev12.pdf

.

MiBrassFS wrote: Thu Oct 23, 2025 1:17 pm I don’t remember needing to plug and drill/tap a Yamaha marching baritone piston. The valve stems are so long that they don’t generally sport the geometry that would strip out the piston. The tuba pistons were also not a problem doing a plug and drill/tap job, but it’s a toss up on those because parts were cheap and available. The time/materials vs part cost made it a customer call.

“High end Chinese”

Heh, heh… bloke’s funny…

Some Yamaha instruments are examples of high-end Chinese, but instead of charging a few hundred bucks for entry level trumpets, they charge 1300 or 1400 bucks for them because they're Yamaha.

I would pick the JP knockoffs of Yamaha marching brass over Yamaha marching brass, simply due to the the way the valves are built... but the JP cases also last longer than a couple of years, as a bonus.
Anyone who's never seen them is going to be skeptical, because they're going to imagine that they're just like other stuff they've seen made in China other than Yamaha Chinese.

Just to go into a little bit of detail, Yamaha marching brass pistons are completely lead soldered together and then nickel plated. Anyone who might try to silver braze an insert in the top of a Yamaha piston and then re-drill and re-tap is going to be in trouble, because they're going to end up un-soldering the piston from itself.

JP Pistons are stainless steel and tolerances are really excellent.
Yamaha tolerances are also very good but again they're just held together with lead solder and they're not as stable.

As far as extracting busted off stems from either of these, I tend to sharpen a narrow screwdriver really sharp and tap pretty smartly into the broken off stem, and then just unscrew it with that same screwdriver. It works about 80% of the time if not more often. The JP threads are .7mm tpi whereas Yamaha are .75 tpi.

As far as American marching brass is concerned, I'm really impressed with the defunct Kanstul mellophones, but their stuff all tends to be very delicate and easy to tear up.

King mellophones are probably the second best - including all makes from all countries. I generally like King marching brass. I'm saddened that it seems to be made now by employees rather than by craftsman.

I just don't understand the paper thin sousaphone bodies that have been made in the United States for around four decades now. The JP knockoff of the King sousaphone is a considerably higher quality knockoff than the Taiwanese copy, the JP sousaphone valve sections are actually superior to King (which these days isn't difficult), and JP bodies are enough thicker than King bodies so as the JP sousaphone's weigh about 2 lb more than King and don't dent as easily.

As far as valve sections are concerned, I'd be happy with a JP sousaphone valve section stuck on a King sousaphone, I'd be happy with the JP valve section from their C tuba stuck on any European York style valve section C tuba. I'll be fine with their rotary valve sections installed on any other instruments from any other country. I'm just a little bit annoyed that JP rotor stop arms aren't really tight on JP rotor valve stems, but - in the past - this was an issue with Miraphone as well (clicking noise unless the center screw is tightened).