TubaForum.net

Is there enough material on, say, something that looks like a Bach 18 that it could be sanded down to fit in old English receivers?

Could an aspiring at-home tinkerer do this with fine grit sandpaper?

http://forums.chisham.com/viewtopic.php?t=10390

According to this post about outer diameters the small end of the shank... you're trying to get from .520" to .490"... that's a difference of 0.03", which is a little less than 1/32".

First -- I would measure the thickness of the metal at the shank of your mouthpiece
Then subtract 0.015" (half the total, since you're measuring just the thickness on one side) and see what's left
No idea what the measurements would be like, but maybe it'd work out okay? Or maybe it'd be too thin? Or maybe physically possible but just really awkward or difficult to do (and do well/consistenly)
I don't think fine sandpaper is necessarily the tool of choice here

I think my question for this would be, what's the *inner* diameter of a typical British shank mouthpiece vs American shank mouthpiece? Because as shank size increases, it's not like the inner diameter stays the same. The metal thickness across shank sizes is probably comparable, but the inner diameter changes.

Some mouthpieces (like Monette) have really thick walled shanks though. Thin-walled... IDK...

I'd probably turn down most mouthpieces.

arpthark wrote: ↑Tue May 23, 2023 12:15 pm Is there enough material on, say, something that looks like a Bach 18 that it could be sanded down to fit in old English receivers?

Could an aspiring at-home tinkerer do this with fine grit sandpaper?

No, it’s not a job for a home tinkerer.

It’s not unheard of for a mouthpiece to be turned down (in a lathe by a competent machinist) but the shank can become overly thin at the end and need to be trimmed back.

At one point I had a Bach 24W clone that had been turned down to suit a small shank receiver, it worked (fitted fine, etc,) but as I didn’t get on with the rim I sold that mouthpiece - IIRC I covered my costs.

If you have an Bach 18 to spare, enjoy using them and can get one turned down by a skilled person then that route is worth considering; it’s a gamble but it might end up being OK for you ‘cause similar has worked for others.

I agree with Prof. tofu...

(except...) if it's just a Bach 18 knockoff (if not a "my gawd, this Bach 18 knockoff is magical !!!"), you could (??) try your hand at sanding it down...

- use cloth-backed "roll" sandpaper
- c. 250 grit offers quick progress, yet not too fast, and not too rough.
- keep changing pieces (to keep from using worn grit, so your sanding remains at the same rate.
- mark the outside of your rim (12 - 3 - 6 - 9...or more numbers), and keep track of which sides you've sanded, and do your very best to sand each portion of the rotation (including up-and-down) evenly.
- check with calipers for progress and for maintenance of roundness.
- finish off with 1000 grit or finer
- put a towel on the floor, so - if your mouthpiece spins off your makeshift fixture - it has a soft landing.

THIMK: Rattling in the receiver indicates that the small end isn't being taken down as much as the large end...but TYPICALLY the OPPOSITE is what tends to happen with hillbilly shank sand-downs.

IF (??) you actually have a way to spin the mouthpiece between centers (actually ON CENTER and WITHOUT marking it up), you're likely to sand it more evenly, but (again) change out your strips to fresh sandpaper when they wear down.

(Wear googles and one of those not-effective-at-all-for-viruses-but-effective-for-brass-dust masks.) Also, wear long sleeves, because that crap can get into your skin...particularly the tender skin on the insides of your elbows...