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Bell tenon not round

Postby KingBassTrombone » Mon Jul 22, 2019 4:37 pm

I just received a 1933 York 706 in a trade. The bell tenon on both the bell and body is slightly flattened at the rear. The bell still fits, but doesn't easily rotate and sometimes leaks quite badly. How could a home-gamer go about making it round again?
1933 York 706 BBb tuba (adjustable rec. bell)
1902 C.G.Conn Elkhart & New York BBb HeliConn
1873 Evette & Schaeffer 4v Bb Bass Saxhorn
...and more than 15 other low brass...
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Re: Bell tenon not round

Postby bloke » Mon Jul 22, 2019 5:58 pm

Beat the flat spot out - from the inside - with a BARM (big-@$$-rawhide mallet...such as one with a 2" diameter head).

If you want to get really picky (once improved) you're going to need to measure the diameter at all angles, and mess around until the diameter is as close to the same - every way measured - as possible.
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Re: Bell tenon not round

Postby YORK-aholic » Tue Jul 23, 2019 12:07 am

I once turned a circle out of wood to the correct diameter on the lathe and worked that in. Make sure to drill a decent sized hole in the middle so you’ve got something to grip when it’s time to take it out. Otherwise it makes a really effective mute.

You could do the same by rough cutting the circle with a jig/Sabre saw or bandsaw then using a disc or belt sander to get it just right.

Probably not the “right” way, but given that it worked, it’s not the wrong way.
Some old Yorks, Martins and maybe a rotary King...
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Re: Bell tenon not round

Postby bloke » Tue Jul 23, 2019 11:16 am

To get a tenon pushed back out out to the correct point, it must be pushed - via some sort of of force - out PAST the correct point, which is why the wham-o method has a chance (depending on skill) of getting a tenon close to perfectly round.
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