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I'm in a predicament here. One of my bits for my 1917 Conn 32k has cracked (the gold one pictured). This bit is not original to the horn and was a "shop special" from the repair guy where I purchased the horn. The horn only came with one original bit and the original neck.

I have tried ordering new bits for Conn sousaphones and the bore size is too large to fit fully into the neck receiver correctly. However, in trying that, I realized that it immediately got the horn closer in tune and that the gold bit is the reason I have been perpetually sharp. You can see the wear on the bit for reference as to where it was sitting within the receiver. Ideally this wear mark should be further down the bit for the horn to be brought into tune.

Images are here: https://imgur.com/a/2Z3VTwC

My options are:

• Order every modern bit on the market to see if one of them happens to just fit ($$$).

• See if any of you guys just happen to have some early Conn bits laying around? I will pay of course.

• Or see if anyone can machine me a new bit.

Is there anything else I am not thinking of here? Like getting a new neck with a larger receiver? Or having a shop modify the receiver on the neck?

And before some of you say it... not all sousaphones need to be perpetually out of tune. This is my main horn so it's important to me to make it sound the best it can.

Thanks for any help you can provide!

Ordering new bits - You need to order for the Conn 20K. The modern 36K is just a rebadged King and that’s probably why they didn’t fit.

The first thing I did was order bits for the Conn 20k, and unfortunately those are the bits that didn’t fit. They only go a few millimeters into the receiver.

Before you order anything, please see my private message. New bits are not made the same.

If that instrument is small shank and actually small size (as I've rarely encountered with some obviously Conn-made sousaphones from very far back... I can think of a Blessing stencil .625" bore E-flat sousaphone, in particular)

I have some weird little tuning bits here (I'm sure they were NOT made by Conn) that are roughly in that shank size range.

I'm NOT encouraging you to buy them from me, because I really don't ever want to see them again, if they didn't quite do what you would expect them to do.

The mouthpiece is a small shank / old English shank / bass trombone shank mouthpiece, and - as you can see it - only barely adequately inserts into these two (basically the same size but mismatched) very small tuning bits.

Actually, I would probably more describe these two random small shank bits as being what people would describe as "English shank euphonium" shank size (in between standard shank and bass trombone shank size).

I honestly have NO idea what you need, and - most likely - it is NOT these:

I’m curious what your 36K looks like. Isn’t that a fiberglass sousaphone? Did they recycle the model number?

@bloke Thanks, but I don't think those will work. @iiipopes has one sitting in a box that looks really promising so I am starting there.

@arpthark Here's some images. https://imgur.com/a/61feqoW You are right, I made a typo in the original post - it's a 32K. I posted it to an antique Conn group and they debated over 32k vs 14k but apparently C.G. Conn didn't make 14k's in 1917. I'll fix the typo in the original post.

As I sit here, in front of me is what appears to be an original neck from a @1926 Pan Am, which has the .687 bore, not the now-standard .734 bore. The Pan Am is roughly the student version of a 32K, predecessor of the Cavalier, 14K, and fiberglass 36K. The neck is proportioned differently to current manufacture. The bit I am sending to blacksheep has, from years of use, the line on it indicating proper insertion depth, just shy of one inch. It inserts perfectly on the Pan Am neck. Neither the bit nor the neck appear to have been altered or abused or repaired in any way, and they have the same external contouring at the insertion point on each.