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Technical Operations Bulletin AT308, Inc. TOB#:822

Threaded inserts, also known as helicoils, are used to repair damaged threads in three steps. The inserts have an inner coil diameter that matches the desired thread size. A tap is made that matches the outer coil thread. The insert is installed by first drilling out the damaged threads and tapping the hole. Then, the insert is screwed into the hole using an installation tool and leaving the insert in place when unscrewed.

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192 views2 pages

Technical Operations Bulletin AT308, Inc. TOB#:822

Threaded inserts, also known as helicoils, are used to repair damaged threads in three steps. The inserts have an inner coil diameter that matches the desired thread size. A tap is made that matches the outer coil thread. The insert is installed by first drilling out the damaged threads and tapping the hole. Then, the insert is screwed into the hole using an installation tool and leaving the insert in place when unscrewed.

Uploaded by

mikadoturk
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Technical Operations Bulletin AT308,Inc.

TOB#:822

Helicoil Installation

Threaded inserts are used to repair damaged blind hole threads using three steps. Inserts (basically
coiled wire) have been constructed so that the ID of the coil matches that of the desired threads. A tap
is then fabricated to match the thread resulting on the OD of the coil. A small tab (B) is placed on the
bottom of the coil to aid in installation.

Instalation includes, first the damaged threads are


removed by drilling. The hole is then tapped to
accept the insert. The insert is then screwed onto
the installation tool and the toll is then cscrewed
into the newly threaded hole. When the
installation tool is unscrewed, it leaves the insert in
the hole being repaired.

Thread Repair Insert Philosophy

Thread Insert
Insertion Tool

Page 1 of 2
Rev.:01
AT308,Inc. Technical Operations Bulletin
TO#:822

The following discussion is based upon the repair of 3/8-16 thread.

a. The hole with the damaged threads is enlarged with 25/64 or "V" bit from the
thread repair kit. The specific drill size-thread size relationship is indicated in the repair
kit instructions.

b. The enlarged hole is then tapped with the taps from the appropriate repair kit.
Look at the taps carefully. The tap that has the longest lead should be used first to start
the threading process. After the starting tap has "bottomed" out. Used the bottoming
tap (the tap with the shortest lead) to finish the threads to as close to the bottom of the
hole as possible.

c. The thread insert is threaded in place with the use of the installation tool. The
tool has a slotted bottom in which the heoilcoil tap rests during tightening. The helicoil
insert tab (B) need not be removed.

Page 2 of 2
Rev.:01

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