TromboneChat

Hi to all.
I have such a question. I purchased a top 7ST and a backbore ST1 from two different sellers. But for some reason they do not fit together.
I used to have a ST2 backbore and used it with this top.
Can you please help me in this matter?

You might just need to clean the threads. Might be a little excess plating in the threads. Try some kind of oil, and slowly work the backbore into the top a little at a time. Something like key oil.

Slidehamilton wrote: ↑Fri Sep 16, 2022 9:44 pm You might just need to clean the threads. Might be a little excess plating in the threads. Try some kind of oil, and slowly work the backbore into the top a little at a time. Something like key oil.

Thanks, but that's probably not the problem. For some reason, the thread on the backbore is larger by 0.2 mm than on the top.

3/8" x 40 tpi if you need a die...

Warburton changed the diameter of the thread many years ago.
I had him make backbores with the old thread diameter for some bass cups I purchased...

Contact Warburton

MTbassbone wrote: ↑Sat Sep 17, 2022 8:30 am Contact Warburton

I'm waiting for an answer from them

I was wondering about this myself, but reversed: on my ST9 top and ST2 backbore they're a little wobbly threading on, as if the tolerances were too loose. Looking at the threads it appears the top had lost it's plating, which might account for the wobble (threads on the backbore are fine). But it threads and is tight once on.

I should note that I bought my setup from the same place.

To the OP: How did your prior ST2 thread on? And what are the threads like on the top? You may be surprised at how little it takes to fill the grooves, especially with such fine threads, with gunk.

Here are a few photos of my set up. You can see where the plating has been lost on the top's threads.