[Shop-talk] What's better than helicoil?

[Randall]

> I
> remembered that a while back on this list there were recommendations for
> other
> types of thread repair kits besides helicoil that were considered better.
> I
> didn't save the information, but wish I did.  Can anyone help with
> recommendations?  I would be looking for a good quality kit for both
> metric
> and SAE thread repair.

Gene,
Opinions vary, but based on a long-ago conversation with a professional
mechanical engineer I believe a properly installed helical insert (Helicoil)
is just as strong as the solid types.  He had a complicated explanation of
how the helical inserts deform under load to spread the load more evenly
throughout the threads, rather than concentrating forces near the surface;
which I don't recall entirely.  But he believed they were actually stronger
than the solid inserts.  No doubt there are exceptions to that rule, and I
should have asked about them, but I didn't.

The solid inserts do have some advantages, though.  They don't require
special tools for installation, and they can be installed into oversize
holes.  Some of them come with a more positive locking mechanism as well.

I keep them in mind as a backup position if I ever have a Helicoil pull out.
In almost 40 years of turning wrenches, the only Helicoil failure I have
ever seen was one that came out with a spark plug.  We used Loctite and
anti-seize (obviously not at the same time) when replacing it with another
Helicoil, and never had any more trouble with that cylinder head.

Randall