Conn 5j valve caps

[York-aholic]

Are there any top valve caps that will interchange with Conn 5j caps?

I’m not loving the 5j caps...

[bloke]

You had to ask this question two days after I returned to 5j back to a school.

[York-aholic]

You had to ask this question two days after I returned to 5j back to a school.

[bloke]

You had to ask this question two days after I returned to 5j back to a school.

no worries, they'll tear it up again soon.

[York-aholic]

They are definitely bigger than Olds/King, but just slightly smaller than Holton 340/345 and York .750 bore valve casings.

Not an emergency. I have all four 5j caps and am fully functional.

[bloke]

What about the threading of 14K/34K/36K/38K caps?

I'll measure a 5J cap (if I can find one) against those, and then eyeball the TPI.

If the i.d. is the same, I would consider it unlikely that the TPI would differ.

If the sousaphone caps (definitely more elegant) are also lower-slung (top of risers might be lower...??), you can simply cut that difference off the stems...I've done this when tossing King top caps in the King parts drawer and screwing on Olds O-99/Bach 869 caps.

[bloke]

REPORT:

Sadly (nonsensically, in my view), the 5J thread size is slightly different from the legacy Conn sousaphone threads.
(I'm thinking the first 5J's were made when the Abilene factory was set up, no?)

Neither are those the same threads as Buescher/Bundy/Selmer/Signet threads.

To improve them, you'll probably need to take them to a friendly machine shop or guy-with-a-lathe and ask them to remove the turret walls from the caps and then add some knurling back to them (or carefully hacksaw them off and then artfully file, sand, and buff the chopped-off remainders).
Assuming a machine shop or lathe-owner, you'll probably want the sides knurled, since the knurling will have been cut off and discarded.

Since the center risers of the 5J top caps are so narrow (obviously depending on the thick felt donut washers, rather than the risers), you'll also need to have them bore some 5/8" o.d. cylindrical brass with a .440" i.d. hole, so that very short pieces of the proper length can be cut off that subsequent brass tubing, slipped over the o.e.m. risers and soldered into place (for a decent "foot", onto which your button felts can impact).

[York-aholic]

Thank you @bloke for figuring all that out for me!

I can do the lathe work, minus the knurling. Once I get the rest of that project up and running, I’ll look at valve cap modifications. “Pimp my valve caps”

Thank you again.