You need a gadget called helicoil Chuck. You have to drill it out and re tap with
a special tap and then insert the Helicoil.

Paul Lamar

Paul, Let me turn everyone here onto a really GREAT thread repair
system. Chuck Heli-coils do work but they are a very old-tech
item. They do work ok when used very carefully. Since the helicoil
is a wound sping of diamond shaped wire they can be snagged
on one end and stripped or pulled out.

The item we all want is called a timesert. I don't work for
these guys but I would if they asked me! They make a special solid
insert that takes no more room radially than a standard Helicoil
but is at least twice as strong. They invented mechinery to
time the cutting of threads where the outside thread goes out
the inside also goes out. The resulting thin steel sleeve is made
so the last inside thread is un-formed. After cutting the new
thread a roll tap is run thru the ''sert" and swages the bottom
into the hole. Sorry for being longwinded on this one but
these things are so much better than Helicoils you can't believe it.

The Kawasaki mgmt. was so impressed the sold them thru the
dealerships. This was the only time I ever saw Kawasaki sell anything
from an outside vendor that they didn't own!
Check them out at www.timesert.com you will be glad you did.
Bill Jepson

Paul, Bill is absolutely right on this. I've used Timeserts for 
ten years and have had them installed in the spark plug threads
of my Harley for over 9 years. Timeserts are 21st century technology, 
while helicoils are 19th century. As an inspector who
fought vendors installing helicoils for five years (in one of 
those former lives) the big thing that sets timeserts apart is
that once installed they can be gauged to certify that the 
installation is correct and has restored the threads to original
condition. 

Not so with Helicoils, you must torque a screw into 
the hole to set the insert. If it's wrong the helicoil may very
well back out, or worse yet gall themselves into the hole THEN 
back out, bringing your freshly cut oversize helicoil thread form
with them. Not you are truly "up the crick" as my grandfather 
used to say. In my search to determine how best to inspect
Helicoil installations, I found that the US Navy only allows 
a screw to be inserted into a Helicoil twice and then the part is
decertified, i.e. scrap, regardless of the condition of the 
threads, which tells me these things can simply not to be trusted
for the long term where a screw is to be service removable.

My friend Steve, the Porsche fanatic, told me about Timeserts 
when he installed them in his engine cases on the recommendation
of his mechanic to insure that no studs would be pulled out 
when he put high compression pistons in his 911S. You might try
checking out some of the German car high performance shops 
in your area if you only need one thread fixed.

Rick Girard

 
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