Fixing a leaking neck joint

[jrintaha]

My alto's been stuffy sounding and difficult to play for a while - probably caused by getting it knocked over by yours truly.

I've checked for pad leaks several times, and suspected the neck joint, but wasn't fully convinced until I stuffed a teddy bear down the bell and tried to play a low Bb, and heard a stuffy, faint, high sound coming from somewhere. I tried opening the palm keys just a teeny weeny bit to figure out where the leak might be (could be the body octave pad too, it's difficult to check with a leak light), and indeed the sound was higher than what was coming out of the palm F slightly opened. The neck octave pad was a tight seal even at extreme pressures, so it must be the neck joint.

So I started looking at it and noticed that while the neck tenon itself looks perfectly round (did not check with calipers yet, as I can't seem to remember where I put them...), the neck receiver doesn't. So I wrapped some tape around the neck receiver and started hammering it carefully with a small hammer, testing the fit every couple of bashes. It took quite a while, but I finally managed to get the stuffiness out of the tone and the low notes sounding easily, even at small volumes. The lacquer took a bit of damage, but as the horn is from the 70's, and has been played a lot, the lacquer is already halfway gone, so no big deal.

The question is, what's the proper way to do it? Should the neck tenon be expanded with a dent rod / ball that is the tiniest bit too large to fit through, or should the octave key mechanism be removed from the body, and the neck receiver compressed to make the neck fit better?

Cheers,
Jori

 

[jbtsax]

The question is, what's the proper way to do it? Should the neck tenon be expanded with a dent rod / ball that is the tiniest bit too large to fit through, or should the octave key mechanism be removed from the body, and the neck receiver compressed to make the neck fit better?

You have raised two issues, the neck receiver being out of round, and the neck tenon fitting too loosely. I'll address them one at a time.

The way I was taught to reshape a receiver is to use hard steel pin plugs that are graduated in .001" increments. You find the largest one that can be inserted and tap the top edge of the pin with a plastic or rawhide mallet. This moves the brass that is in contact with the pin on just 2 sides since it is slightly oval shaped. This process is repeated with the next larger pin and so on until tapping the pin that just fits no longer allows the next larger pin to go in. When the receiver is badly out of round, it is best to unsolder it and replace it with a new one if one is available.

The above process is always followed by carefully expanding the male neck tenon. The most efficient way to do this is with a "can opener" type expander pictured below. Once the neck tenon has been properly expanded to fit a perfectly round receiver, it will be completely airtight even when the neck tightening screw is loose. The real purpose of that screw is to keep the neck from turning. It does not form a seal when tightened, in fact in many cases it does exactly the opposite if there is a "bubble" in the receiver just below the slot.

All of this may come as bad news to the do-it-yourself crowd, but there is no substitute for having the right tools to do the work correctly. Part of the fee you pay for professional work is to compensate for the investment in tools and equipment that have made the quality repair possible.

 

[kevgermany]

All of this may come as bad news to the do-it-yourself crowd, but there is no substitute for having the right tools to do the work correctly. Part of the fee you pay for professional work is to compensate for the investment in tools and equipment that have made the quality repair possible.

Even though I'm a do-it yourselfer, I agree.

I guess it's the same for flutes?

 

[jrintaha]

jbtsax, thanks for the informative answer once again.

I already figured out you need specialist tools for this kind of job, but as always I'm interested in what kind of tools exactly. Apart from the lacquer loss, I did get a pretty good end result with just hammering, but there's still a tiny leak right where the slot below the tightening screw is - the playability improves slightly when I place a speck of blu-tack there. Lining the rest of the neck joint with blu-tack does nothing.

I might try to get it better now that I found my calipers - I can measure a difference of slightly less than 0.1mm between the widest and tightest points in the receiver. Will take forever, but I've got time on my hands now. It's not as if I could really play my tenor with the way my back is still hurting, so I might just as well try to get the alto in good working order.


Cheers,
Jori

 

[griff136]

Even though I'm a do-it yourselfer, I agree.

I guess it's the same for flutes?

basically it is Kev.

http://www.youtube.com/watch?v=cPh37-SM14w

 

[kevgermany]

Thanks Griff. I asked cos my wife's flute has a receiver that's tapered - but tighter at the head joint end than the body end. One repairer (not a flute guy, though) said it was beyond repair, but maybe not. I fixed it temporarily with some stick on copper tape from Smiths inside the receiver, but thought a better solution must be around. Guess I need to go to a flute specialist.

 

[jrintaha]

A small update: I managed to get an airtight, if ugly and probably not permanent solution: I brushed a very thin coat of super glue on the neck tenon after having cleaned it, then let it dry completely. Then I started inserting the tenon into the receiver, sanding carefully with 1500 grit sand paper every time it would not slide further down, then trying again and sanding a little and trying again and again and again...

Quite a lot of trouble for something a skilled tech would have fixed very quickly (and neatly I might add), but as it is now I can't move around very easily, so taking it to a repair shop would have been even more difficult. Plays better than ever now, could be there was a tiny leak in the neck joint in the first place, which was made worse (and noticeable) by the fall. Who knows.

 

[kevgermany]

I've noticed this - badly fitting neck and the result is an instrument that plays badly. Hope your repair lasts! And that you're well on the mend.

 

[aldevis]

This subject is a bit creepy: I always thought that expanding a tenon would change the inner volume of the neck.

Any other material alternative to superglue, for a worn tenon? I was thinking of some kind of PTFE paint.

 

[kevgermany]

This subject is a bit creepy: I always thought that expanding a tenon would change the inner volume of the neck.

It will, and changes the id. Question is, is the change significant, cos it's at the top of the sax where things are most critical.

 

[jrintaha]

I did not expand the tenon in this case, as I just painted the outer side with super glue. So the inner dimensions should remain exactly the same. So in a sense this was a "safe" kludge.

 

[griff136]

It will, and changes the id. Question is, is the change significant, cos it's at the top of the sax where things are most critical.

As the tuning of saxophones is a compromise and is dependant on a load of factors -reed strength, mouthpiece chamber dimensions,embouchure, position of the mouthpiece on the crook cork,key heights and venting,ambient temperature etc, a miniscule change in the crook tenon internal diameter won't have any detrimental effect.

Using the "Tin Opener" style expanding tool is a common procedure to rectify an ill fitting/loose crook tenon.

 

[aldevis]

As the tuning of saxophones is a compromise and is dependant on a load of factors -reed strength, mouthpiece chamber dimensions,embouchure, position of the mouthpiece on the crook cork,key heights and venting,ambient temperature etc, a miniscule change in the crook tenon internal diameter won't have any detrimental effect.

Using the "Tin Opener" style expanding tool is a common procedure to rectify an ill fitting/loose crook tenon.

This is what all the technicians say, like ladies that state "we are only having an affair, I will not try to kill you if we split".

But is there an alternative, adding material to a worn tenon?

 

[jbtsax]

But is there an alternative, adding material to a worn tenon?

Worn valves on quality brass instruments are sometimes given a thick plating and then "lapped" to fit the casing. I have never heard of this being done to a saxophone or flute tenon. It is important to understand that the typical neck tenon expansion is generally .001" or less to achieve an airtight fit. In many cases only selected areas are expanded according to the pattern created by lapping which shows the high and low spots. In any event, it would be only those few notes whose pressure anti-nodes are located in the area of the neck tenon that are affected, and then only to a minimal degree.

 

[Morgan Fry]

Any other material alternative to superglue, for a worn tenon? I was thinking of some kind of PTFE paint.

Cork grease. PTFE tape is too thick IME.

Sure, expanding the tenon will alter the acoustics slightly. But the cylindrical tenon is a compromise anyway, in any case it won't be nearly the problem the leak is. If you are very concerned you could always paint the inside of the tenon after expanding it.

 

[jonf]

Using the "Tin Opener" style expanding tool is a common procedure to rectify an ill fitting/loose crook tenon.

Indeed. I watched Griff doing just this on my elderly Yanagisawa alto - the sax came as a wreck for £80 without the neck, and Griff expanded a new one to fit, as well as sorting out all the leaks. Result - superb sax, plays brilliantly.

 

[griff136]

Indeed. I watched Griff doing just this on my elderly Yanagisawa alto - the sax came as a wreck for £80 without the neck, and Griff expanded a new one to fit, as well as sorting out all the leaks. Result - superb sax, plays brilliantly.

Thanks for your kind words Jon🙂