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Re: Helicoils and TA's (again)

To: "Foster, Stan" <stan.foster@hp.com>
Subject: Re: Helicoils and TA's (again)
From: "Robert M. Lang" <lang@isis.mit.edu>
Date: Tue, 11 Jul 2006 12:48:22 -0400 (EDT)
On Tue, 11 Jul 2006, Foster, Stan wrote:

> I've read all the posts going back a couple of years on this topic and
> amazingly I still have questions..

Mes ouis.
 
> I have to fix one loose stud and I have the 5/16x24 helicoil kit that
> conveniently  comes in a pack of 12....

Yes, def. convenient.

> I was wondering if the hole for the defective stud actually needs to be
> drilled further or if I can just use the tap in the existing hole to cut
> the thread for the helicoil ?

The hole in the TA does not need to be drilled futher.

However, the special heli-coil tap is not a "bottoming tap". so it doesn't
go deep enough in the hole to get the good part of the threads. SO, you
have two choices: 1. tap carefully and stop running the tap in when it
gets hard to turn OR 2. carefully remove the pointey tip on the heli-coil
tap so you can get another turn or two when you run the tap in.

I modified my heli-coil tap for the latter.

> I also wonder about breaking off the tab that is used to screw the coil
> into the hole. Since the hole is a dead-end can this tab be broken off
> and if so how, or is it just left in place ?.

You def. want to break the tab off the helicoil once it's in the hole. It
can be safely snapped off and then just blow the crud out with some
compressed air.

> Finally, I have 12 helicoils, should I leave well alone and fix the one
> broken one or go for broke and do them all now while I have the thing
> apart ?

Don't do more than you need, but make sure the other holes are okay. If
you see "galling" on the threads in the TA, you should def. consider using
a heli-coil because it's just a matter of time before the threads "wear
out" and you can't get a torque setting on the stud/nut.

If the TA is out of the car, then it might be worth paying a machinist to
drill the holes and install the heli-coils.

Word of warning: be SURE that the studs are square to the TA, because if
they get cock-eyed, it's a PITA to install the hub carrier! Note: this is
NOT experience talking... nooooooo. :-)

But to help make sure you get the hole in the right place (and square),
it's def. worthwhile to make up a jig so your drill doesn't get "tipped".
I can post details (again) if necessary.

> Stan

Bob "How did I cock up that TA Stud" Lang
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