The slide tenon on my 1947 Vocabell slips even when the tenon nut is tight. Is there a home repair for this, or should I take it to a professional? This is a very nice vintage horn, and I don’t want to take any chances with it.

I would suggest taking it to a good tech. If you must DIY, you could file off a millimeter (1/16 inch) from the end of the tenon, which will make it go further into the receiver and may make things firm up a bit. Remember to clean up any shaving you do to remove any burrs.

[quote="BGuttman"]If you must DIY, you could file off a millimeter (1/16 inch) from the end of the tenon, which will make it go further into the receiver and may make things firm up a bit.[/quote]

That is assuming the end of the shank is the issue. It may be that the shank is worn so that the threads contact the slide receiver. In this case, the repair is a little more complex.

[quote="hornbuilder"]<QUOTE author="BGuttman" post_id="166348" time="1640359882" user_id="53">
If you must DIY, you could file off a millimeter (1/16 inch) from the end of the tenon, which will make it go further into the receiver and may make things firm up a bit.[/quote]

That is assuming the end of the shank is the issue. It may be that the shank is worn so that the threads contact the slide receiver. In this case, the repair is a little more complex.
</QUOTE>

Quite true. In either case a layer of plumber's tape (or two) around the tenon could be a work-around. Not a good permanent solution, though.

But first try the obvious.

Clean it thoroughly, not with abrasives but with dish soap and soft brush or similar.

Insert it firmly. The old horns were friction fit and that still is how the trombone works, the screw fitting just keeps it from loosening.

And then try something counterintuitive, but easily reversed. This was suggested by a frequent contributor here and works for some people. Lubricate the tenon. That lets it get to the right spot. This obviously won't work if it is worn down, but you can clean it off if it doesn't help.

And if plumbers is a little thick, good 'ol Scotch Matt finish magic tape lets you start thin and add layers. Lasts a surprisingly long time and is easy to clean off.

Be careful when using “Scotch” brand tape on brass instruments. Yes, it will work as a temporary shim on a tenon and can be removed. However, Scotch tape can create problems with some lacquered surfaces. I have seen many student instruments that were decorated for festive occasions. The Scotch tape can pull the lacquer off. It’s a shame to see to see an instrument with Scotch tape scars that otherwise has a near perfect finish.

[quote="Crazy4Tbone86"]Be careful when using “Scotch” brand tape on brass instruments. Yes, it will work as a temporary shim on a tenon and can be removed. However, Scotch tape can create problems with some lacquered surfaces. I have seen many student instruments that were decorated for festive occasions. The Scotch tape can pull the lacquer off. It’s a shame to see to see an instrument with Scotch tape scars that otherwise has a near perfect finish.[/quote]

Not as much a problem on the tenon -- most of them aren't lacquered.

If the lacquer peels off with tape there is an adhesion problem with the lacquer. In fact, that's a test for proper surface preparation.

The variable that is a wild card with adhesives is time. I have seen electrical tape (although I don’t necessarily recommend it) used to shim press-fit leadpipes. If removed in the first couple of weeks, it comes off just fine. If left on the leadpipe for a few years, the adhesive can actually etch into the brass (unlacquered).

Don’t get me started about masking tape….as an educator, I have seen a lot of it over years. If removed in the first couple of hours, it will come off easily. If left on something long enough, the adhesives in masking tape will destroy everything in it’s path.

My point is that Scotch tape, especially combined with time, will pull off even the best of lacquer finishes. I see this regularly with the student instruments that come through my shop. Full disclosure, most of the Scotch tape that I see on lacquer appears to be well-aged. For this reason, I always ask if the musician wants it removed and I explain the risk of it pulling off the lacquer.

Back to the original topic…yes Scotch tape can be used as a temporary fix on a tenon, and the tenon should not have lacquer on it. The longer the Scotch tape is left on the tenon, the more messy the removal will be. The best way to remedy this is to get the horn to a tech. You are probably just postponing the inevitable…..like the need for a properly sized male taper on the slide side (as Matthew already stated).