Stupid Mechanical Question

[Kneale Brownson]

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Helicoils ( http://www.irwin-ind.com/helicoil.htm )  and Timeserts (
http://www.timesert.com/ ) go into a larger, specially-threaded hole than
originally was tapped into the receiving part and are sized to provide the
inner thread of the original hole so that you can use the same fastener.

Helicoils are a wire insert that screws into a thread created by a special
tap.  The installation tool breaks off the tang used to thread the coil
in.  Sometimes folks add an adhesive.    The wire coil is formed so that
its inner surface forms a new thread.  I had Helicoils installed in the
spark plug holes of a Mercedes aluminum head from the back side (head off)
because the tech said they'd be most likely to survive that way.  I
replaced spark plugs in that head for several years afterward with no problems.

Timeserts are a bushing with inner and outer threads that also go into a
larger hole that's tapped for the outer threads.  I think they have some
mechanical anchoring device.  The BMW cycle list I read regularly has had
numerous postings on repairing aluminum threads used with the fasteners
that hold the cylinders to the blocks, and the consensus seems to be that
Timeserts are more reliable than HeliCoils for that application.

At 08:09 AM 07/26/2002 -0400, TM wrote:

>Can someone tell me the principles and the actual procedure
>on how a helicoil works?
>
>Thanks,
>Taka
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