Stripped a thread? You need an in­sert

Alu­minium threads have a nasty habit of strip­ping just when you don’t want them to. Here’s how to fix them for life with thread in­serts

Practical Sportsbikes (UK) - - Contents - WORDS ALAN SEE­LEY PHO­TOG­RA­PHY ALAN SEE­LEY

EVEN THE MOST cau­tious me­chanic and fas­tid­i­ous ap­pli­cant of the torque wrench will oc­ca­sion­ally strip a thread. It’s frus­trat­ing and you never quite get used to the stom­ach-lurch­ing sen­sa­tion when a thread gives way just on the point of a fas­tener tight­en­ing.

Still, it’s all fix­able and there are a num­ber of thread in­sert so­lu­tions on the mar­ket. ‘Heli­coil’ has be­come the generic term for stripped thread re­pair, much as ‘Hoover’ is to vac­u­um­ing and ‘Sel­lotape’ is to ad­he­sive tape. The ba­sic prin­ci­ple of all is that the stripped-out thread is re­placed by en­larg­ing the hole, tapping it over­size and fit­ting an in­sert with the same size and pitch as be­fore. It’s a far more el­e­gant so­lu­tion than the once-pop­u­lar bodge of tapping a hole out to take a larger fas­tener.

An­other ben­e­fit of a threaded in­sert is that it of­ten of­fers a much stronger thread than was there be­fore, par­tic­u­larly when go­ing into alu­minium.

How­ever they do have to be fit­ted cor­rectly for the fas­tener to work as de­sired. If the hole isn’t prop­erly tapped out, the in­sert can be­come thread-bound or of­fer too small a di­am­e­ter for the fas­tener to go into. It must also be ab­so­lutely con­cen­tric with the orig­i­nal hole or the stud or fas­tener won’t line up with the com­po­nents it holds to­gether.

Here’s how to do it right.

Tools for the job

Cut­ting com­pound. Ham­mer. Drill. Tap. Thread in­sert tool. Tang re­moval tool. Tap

Pete O’dell: a cham­pion of thread in­serts and lib­eral think­ing Only se­ri­ous looking tools for a se­ri­ous job

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