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Re: ABS crack repair

Author: Chris P
Date: 2021-01-11 13:44

The immediate area by the thumb tube is notoriously weak and many plastic clarinets will crack there.

The problems are made even worse as plastic will shrink and expand a lot with temperature changes compared to metal which is relatively stable, so when plastic gets cold, it will shrink and the metal thumb tube will put stress on the plastic. You also have two toneholes (thumb tube hole and side F# tonehole) at the same level within close proximity and that will also be a weak point where the joint can crack.

Another plastic clarinet that has been known to break at this same point are Artley/Armstrong clarinets. They used to have a plastic thumb tube but changed to a metal one and that caused more of them to crack. The older plastic thumb tubes expand and contract at a similar rate to the plastic joint and that puts far less stress on the injection moulded joint.

In essence, plastic and metal just don't mix. If you can successfully weld the crack, then by all means do that - otherwise it's often a lost cause and better to replace the top joint. As well as the weld, you can mill out slots and fit ties across the cracks to reinforce things (like butterfly joints), then hide the ties with filler.

Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.

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