It shouldn't cost you anything - it's down to your school to pay for repair work on their instruments.This is a school owned Series II with the 2 screw deal. It was like this when i got it, so i dont know about any previous damage. How much would it cost to fix this?
So, the correct repair is ... Buy a lathe and measuring tools, as well as a hunk of brass of the approprate metalurgy, preferably from recycled shell casings that were melted then hand hammered into the appropriate sized "billet" before machining. Then machine a new tenon to the appropriate surface finish whilst carefully keeping the metal cool as to not anneal it... Stiring a little more.It's interesting how we are led to believe that minute dimensions are critical in the bore of a sax, yet we are quite happy to expand those tenons and increase the bore diameter in the process.
Sure, with the reinforcing ring around it, it is unlikely that the clamping part of the socket would expand. My thinking was more to do with the lower part of the socket. Sure, it has a little reinforcing from the junction with the body, but to counter that, it is much more difficult to shrink a tube that to expand it. (And isn't the socket often thinner metal than the tenon?) So I rather think that when the bottom part of the socket is lose, causing leaks, it is a either congenital defect or caused by distortion (expansion) of the socket during ab-use.You two are naughty!
Re: the OP's question, my understanding was the act of allowing the neck to move while the screw was tightened (partially, I assume) acted the same as a tech's shrinking die, gradually making the neck tenon smaller. Expanding the tenon *should* return it to its original diameter (which should also address Gordon's problem with "messing with" the bore diameter ).
A can opener type reduces the thickness of the metal. But metal cannot be shrunk in volume, so the can opener reduces the thickness by making the circumference larger. If the circumference is larger, then both the ID and OD are larger, the ID slightly more affected than the OD.the can opener expander acts as burnisher and should provide minimal distortion on the internal diameter of the neck. also my answer assumed the reader knowss, you would only use the expander to take up a very small distance... and also to the question, i assumed you are repairing the original neck which is now loose.
The arguement is that it will make the tenon fit better in the socket and the instrument will therefore respond much better than if the tenon was left loose and leaking.But some guys argue in this forum that minuscule alterations to the bore alter the way a sax sounds.