[Boatanchors] How to repair stripped panel threads

[WA5CAB at cs.com]

John's reply later in this thread is absolutely correct.  The helicoil is the 
preferred method in industry and the military for repairing stripped threads. 
 I've used them successfully down to #2-56 UNC.  The helicoils themselves are 
cheap, and in each thread size come in several lengths.  The dollars are in 
the special tap and the installer and drive tang breaker.

A helicoil is a length of almost (*) square bar coiled up such that the ID is 
slightly greater than the original thread's minor diameter.  The special tap 
has the same pitch as the original thread but a pitch diameter equal to the 
original plus the radial diagonal dimension of the bar.  You drill out the 
original tapped hole with the correct diameter bit, run the special tap through the 
hole, and screw the helicoil into it.  The helicoil has a drive tang bent 
across the inner end that must be broken off after insertion.  If the length of 
the helicoil exceeds the panel thickness, it is best to cut the excess off with 
something like a Dremel tool and abrasive disk.

(*) The bar is actually a "Squashed" square, as standard V-form threads are 
60, not 90 degree.

There are some other methods.  Usable in sheet metal is the nut-sert, which 
is somewhat similar to a hollow pop-rivet.  The drawbacks are that it takes a 
relatively large diameter hole and leaves what amounts to a flat washer on the 
outside surface.  Two others come to mind but are generally only usable in 
aluminum or brass castings and wood.

In a message dated 12/12/2008 11:30:44 PM Central Standard Time, 
texasroadrunner at comcast.net writes: 
> I'm sure this subject has come up before, but couldn't find any hits via 
> google groups.
> Wondering what folks on this list have used to repair stripped threads? 
> I've experienced way too many over tightened fasteners which attach BA 
> panels to their chassis.  Currently I have a bunch of panel screws on a 
> Navigator- some are too loose due to over tightning.    One gent suggested 
> dipping and curing toothpicks in Devcon epoxy and then placing them into the 
> 
> hole before screw insertion.  Short of welding (JB?) a nut on the back end 
> of the threads, looking for other ideas out there.
> 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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