Unlikey to come out on a disk or caliper bolt though as its only restraining a rotational force, not a pulling one. Now a spark plug, well i can see that is likely to come out in time.

Give Marko a toffee apple, he`s right.

The Helicoil will only come out when we take the part apart, the screw binds on the insert and out it comes.

It doesn't matter what the bolt, screw is holding when it is done up the force is a pulling one (tension) and the force is tensile.(pulling it apart)

Wots a Thrapston........................is it a surgical or sexual device?:D