TromboneChat

Any suggestions on how to loosen backbore shanks that are threaded (DE, Ar resonance, LI Brass, etc.). I usually periodically unscrew them, but I lent out a mouthpiece and the person must have really twisted the mouthpiece in the horn, and now the backbore is stuck.

Thanks!

If it's one of mine it has a hex so you can use a wrench.
Can't help you on the others.

Tappy taps with a mallet.

Doug Elliott wrote: Tue Sep 16, 2025 8:15 am If it's one of mine it has a hex so you can use a wrench.
Can't help you on the others.

I wish more did! It's an AR Resonance unfortunately

A strap wrench with a soft, grippy strap (rubber, silicone, or similar) usually works without damaging the shank. Some of the larger ones are difficult to adjust down small enough for a mouthpiece shank, but the smaller ones I've tried work.

Burgerbob wrote: Tue Sep 16, 2025 8:16 am Tappy taps with a mallet.

Yup.

As I often remind folks, do this for a long time. Firmly, but not a whack.

Vibration is what you want. Do it for a couple of minutes. You should be tired after doing it.

Cheers,
Andy

And for the smooth & slippery, tapered AR Resonance mouthpiece, you'll need a grippy rubber interface (after gently tapping).

For my threaded backbores (Doug Elliott, AR Resonance) I keep the threads lubricated with a small dollop of tuning slide grease. And never over-tighten them. Works like a charm.

Good luck.

+1 for strap wrench

hyperbolica wrote: Tue Sep 16, 2025 11:28 am +1 for strap wrench

You may need two strap wrenches. [Have you tried the crushed-ice/hot-water trick?]

Both are true. I've poured hot tap water over female parts and cold water on male parts. I only have 1 strap wrench and it has always worked, not to say its not a struggle.

hyperbolica wrote: Tue Sep 16, 2025 2:25 pm Both are true. I've poured hot tap water over female parts and cold water on male parts. I only have 1 strap wrench and it has always worked, not to say its not a struggle.

You can keep that cold water part.

Doug Elliott wrote: Tue Sep 16, 2025 3:36 pm

hyperbolica wrote: Tue Sep 16, 2025 2:25 pm... I've poured hot tap water over female parts and cold water on male parts. I only have 1 strap wrench and it has always worked, not to say its not a struggle.

You can keep that cold water part.

That might not have come out the way I intended...

We know there is shrinkage.

...avoiding temptation.

For DE parts I hold the cup with my hand and tap the hex with a hammer. Maybe clamp it with a grip and tap the grip with a hammer….?

What the repair techs use is a rawhide mallet; you can buy one for less than $20. Tap firmly but not aggressively in the direction to loosen the threads. Err on the side of less force and more repetition. You can use the same mallet the same way to loosen stuck valve caps, screw-in leadpipes, or any other threaded part. And if it doesn't come loose after a minute or two of repeated tapping you need to take it to a professional.

Anyone know if just vibration will do it?

With my Doug Elliott mouthpieces I use a crescent wrench on a rag on the he nut shank and a rubber sheet jar opener on the rim. Sometimes the rim loosens before the shank and I'll use the jar opener to hold the cup.

Haven't had any stuck problems with any of my other screw mouthpieces (Giardinelli and Warburton).

Posaunus wrote: Tue Sep 16, 2025 11:16 am And for the smooth & slippery, tapered AR Resonance mouthpiece, you'll need a grippy rubber interface (after gently tapping).

For my threaded backbores (Doug Elliott, AR Resonance) I keep the threads lubricated with a small dollop of tuning slide grease. And never over-tighten them. Works like a charm.

Good luck.

On my Elliott threads I use a couple drops of Conn Superslick Plus slide treatment on the threads. The stuff from the Slide-O-Mix small bottle works too. Neither will foul the slide.

JohnL wrote: Wed Sep 17, 2025 8:52 am Anyone know if just vibration will do it?

I mean, we put some machine parts in an ultrasonic at work and don’t even try to get them apart until they’ve had a good shake; but that’s a different case.

In general, threads are often stuck due to some micro surface corrosion that increases the static friction on the threads. Need to break that up a little bit and you can easily undo that clamp load.

For all those adding line to the threads, beware that reducing the dynamic friction during tightening has some other consequences. With lower friction, for each unit of torque, you will be making the joint tighter than you would with dry threads. If this lube dries out; you have just increased the force required to loosen it.

Cheers,
Andy

elmsandr wrote: Thu Sep 18, 2025 6:12 am For all those adding lube to the threads, beware that reducing the dynamic friction during tightening has some other consequences. With lower friction, for each unit of torque, you will be making the joint tighter than you would with dry threads. If this lube dries out; you have just increased the force required to loosen it.

In other words, you can't win? Stuck if you don't lube, and stuck worse if you lube?

Just don't overtighten - and wiggle the joint regularly - I guess.

If you do not lubricate the threads with a tuning slide-type grease, moisture will accumulate in there. That moisture will eventually turn into calcium and lime making a home in the threads. So it is a choice. Put a lubricant in there that should make it waterproof and remain stable for a long time.....or...... put nothing in there so that calcium and lime deposits can find a home. I choose a lubricant.

I have been using threaded mouthpiece components for over 40 years. When they get stuck or a little tight, I tap the area with a very small delrin hammer. It might take several hundred taps, but the vibration will always knock it loose. Vibration is the most effective way to break up any binding particles in those threaded connections. I still have that same little delrin hammer that I bought in the late 1980s.

This thread is a minefield of euphemism.

elmsandr wrote: Tue Sep 16, 2025 9:04 am

Burgerbob wrote: Tue Sep 16, 2025 8:16 am Tappy taps with a mallet.

Yup.

As I often remind folks, do this for a long time. Firmly, but not a whack.

Vibration is what you want. Do it for a couple of minutes. You should be tired after doing it.

Cheers,
Andy

I think vibration is combined with the small amount of force, I'm not sure it will work alone.

But you could try putting some lube on it and letting it vibrate a long time. I had a thermometer that would not shake down. It had been delivered with a separated fluid. I taped it to the side of my clothes washer and let it go through a
couple of cycles. That worked but if you have an expensive washer that doesn't shake it might not. I'm using a 1990 Maytag that I've repaired a few times but still works well, but it does vibrate on the spin cycles.

harrisonreed wrote: Fri Sep 26, 2025 5:21 pm

This thread is a minefield of euphemism.

I mean, there’s a whole ‘nother thread asking when it is big enough.

Now I want to devise a test of vibration only for freeing a stuck shank or two. I rarely get mine stuck anymore. I do lube the threads, usually with my rotor or key oil at about the same frequency (not enough).

Like Brian, I’m going on a few decades with these and once you figure it out; it is no longer an issue. Probably have to learn from experience once or twice though to get there. Wish I had learned a little more before I added some wrench flats to my LT H cup. (Don’t do this, it looks silly)

Cheers,
Andy

A couple of small pin holes and a pair of pin spanners would be even better than the strap wrench
https://www.walmart.com/ip/Paramount-PA ... om=/search