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restoring bore at the top of the upper joint to original specification

Author: Reformed
Date: 2026-04-25 20:12

It is common for most wooden clarinets for the bore at the top of the upper joint to expand over use and time.

I have a grenadilla 1010 which has expanded from the cylindrical 15.24mm to 15.50mm.

I also have an ebonite 1010 which is still at 15.24m, probably because the tens are sleeved.

One noticeable effect of this is that the expanded bore instrument has a very wide F/C 12th, the C at the top of the staff is quite sharp. Whereas the ebonite instrument is in tune.

What is the best way to fix this?

I was thinking of a DIY approach through building up layers of a coating and eventually finishing off with a reamer to the right specification.

This raises the question of what coating to use:
- There are "food safe" lacquers but I doubt their durability,
- 2 pot epoxy varnishes would probably work well (e.g. in the UK - Rustins Plastic Coating), but are almost certainly highly toxic even when set
- A liquid shellac would probably also work but finish up being quite brittle

A custom metal sleeve would also work but I am not sure if anyone would take this on.

In my student days, I remember seeing a fellow students Austrian regular Boehm clarinet (not Reform) where the bore was quite deeply lacquered (from one of the Hammerschmidt brothers maybe?) but have no idea what lacquer was used. There were some small chips around the bore ends.

Any comments welcome!

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