Stripped bell screws

[roweenie]

Here's an obscure dilemma:

Two of the three detachable bell screws on my York tuba are apparantly stripped.

I believe it to be an odd thread size (my best guess is 1/4 - 32, as 1/4 - 28 is actually too coarse), so I'm pretty sure that it's hopeless that I'll find something comparable.

I thought of re-tapping the lugs (or bell screw flanges) at 5/16 - 24 and using King screws, but the lugs are quite narrow at 3/8", and there wouldn't be much "meat" left after taking more material away for the wider screws.

So, here's my question:

Is there a bell screw available, measuring between those two diameters (1/4" and 5/16")? Maybe something foreign with a metric thread? At this point, I'll try anything ---

What say you tech gurus?

Thanks!

[Rivercity Tuba]

Go see Matt

[roweenie]

Matt's a great guy, and a first-rate tech, of course. I just saw him last week, regarding another issue.....

Basically, since he's so good, he's busier than a one-armed paper hanger. If it's something I can address, I'd rather not bother him with it - drilling and tapping is well within my parameters (I've rebuilt engines, etc.)



(Yorkmaster on left, York on right)


I'm fairly certain that the bell screw from the B & M Yorkmaster would also be close, but workable (a similar fine thread, and it seems to be a hair thicker, which is perfect).

BTW, there's something about detachable bell Yorks that's never "quite right"....in my time, I've seen several of them that have 3 holes drilled into the bell tenon, to accommodate the bell screws. If you get one that fits without having to do this, it's a special occasion. I think it has to do with the tapered design, FWIW.

[Dan Schultz]

If that horn is like the York 'Master' tubas.... those screws are metric. I might have some in my junk pile. I'll have a look.

Sequel.... I have a few screws that appear to be 6.6mm x .75mm. I think they came from a Marzan (aka York Master). The OD is about .240". I've been known to run in a 1/4-20 tap and use modern bell screws. I can send you four of the bastard size ones I have.