Rifling on Conn 3?

[paysonmcc]

I was going through some mouthpieces for students to use and found a Conn 3 in the pile. I checked to see if it was clean enough to play and found something really cool in the throat of the mouthpiece: rifling! Has anyone seen this on any other mouthpieces?

[ghmerrill]

Brand Turbobore: https://www.mundstuecke.ch/en/

[Olofson]

Glenn Zottola mouthpieces hade riffled backbore. Some of us tried them in the 60s.
Yes that´s right JohnL, not riffled. stepped.

[harrisonreed]

Best Brass also has mouthpieces like this.

[JohnL]

That's a really tight twist.

Best Brass also has mouthpieces like this.

Are those cut in a spiral? It looks more like they're simple circumferential grooves.

Glenn Zottola mouthpieces hade riffled backbore. Some of us tried them in the 60s.

I thought Zottola used a stepped backbore. That's certainly what the patent says.
https://patents.google.com/patent/US2798402A

[Crazy4Tbone86]

At one time, I had a lot of the Elkhart Conn mouthpieces. I don’t remember “rifling” marks like that in any of those. Perhaps someone made some aftermarket modifications with a reamer or a drill bit?

[BGuttman]

I'm certain it was aftermarket. My Conn 3 has no rifling in the aperture (or anywhere else on the piece).

[tbonesullivan]

That really looks like a failed attempt at reaming out the throat. Maybe they used a cylindrical file?

[JohnL]

At one time, I had a lot of the Elkhart Conn mouthpieces. I don’t remember “rifling” marks like that in any of those. Perhaps someone made some aftermarket modifications with a reamer or a drill bit?

I'm thinking maybe a tap?

[timothy42b]

Off topic a bit, but a tap and die set can be useful.

I just helped assemble a handicapped ramp for a neighbor who'd had surgery. It's an assortment of pieces to be used temporarily so gets moved fairly often. The crew ran a tap down every threaded hole and a die across every threaded piece before assembling. That avoided a lot of frustration over munged up or just dirty threads.