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Folks - I just scored a Renolds Eb tuba off of eBay that is missing its bell fastening screws. Does anyone know what size thread they are?

Thanks!

I will say they are a little funky and King screws do not fit, to save you the hassle. I ended up raiding a hardware store to find the thread but I didn’t take note of the size. I wish I could be more helpful than that!

arpthark wrote: Tue Apr 07, 2026 6:17 pm I will say they are a little funky and King screws do not fit, to save you the hassle. I ended up raiding a hardware store to find the thread but I didn’t take note of the size. I wish I could be more helpful than that!

Thanks - I was hoping that I would not have to hauls the thing into the harware store but it looks like that might be the simplest thing to do. I will report on what I find. My guess is 1/4-28 but I don't have any that size at home right now.

Look up 'thread checker' at Amazon. These things are great! I use mine pretty much every week.

So as it turns out, the hardware store had nothing that would fit, and we tried everything, fine, course, metric, English. It's not 1/4-28, 10-32, 4mm,5mm. Some were close but it was clear they were not the correct fit. So the search continues. Why would they not use a standard size? So weird.

LibraryMark wrote: Tue Apr 07, 2026 4:04 pm Folks - I just scored a Renolds Eb tuba off of eBay that is missing its bell fastening screws. Does anyone know what size thread they are?

Thanks!

I had a similar problem with the lear box screw on my Besson Regent which, iirc, uses an 0BA screw. There are tables that identify the pitch, root diameter and outer diameter of fasteners; I have a small Zeus book (Google: Zeus Precision Handbook) that gives such information and bought it over fifty years ago. The root diameter is much the same, if usually very slightly smaller, than the size of the largest drill shank (plain end) that you can push through the hole. Next you need to determine the pitch and there’s a couple of ways to do that. It’s a long time ago but it think I measured the distance covered and using a pointed and bent piece of wire counted the ridges as I pulled the wire along the internal thread. A better method would be to get a match stick (square sliver of soft wood) gently taper it to enter the hole and then revolve it to form a thread on the soft wood, the distance traveled per revolution leads you towards the pitch and the crushed corner sections will guide you towards the major diameter. You will likely need to use a vernier calliper or similar.

I hope that the above helps.