[Shop-talk] Helicoil for plastic?

[Scott Hall]

Background: all the sink and shower faucets in the house are an 
unidentifiable manufacturer. The house was sitting long enough that 
they're all "sticky"--don't want to operate. They pull "up and down" or 
"in and out" to control water flow, then rotate to control temperature, 
not the "ball" type that pivot up to control flow, then swivel. I've 
never seen the kind I have before.

They're all sticky (don't want to turn on/off), but the worst is the 
bathroom shower I'm using. I've pulled out the control knob several 
times. It is fastened to the control valve with a stainless screw into 
what looks like the phenolic valve. I suspect that I'm destroying the 
screw threads in the valve each time this happens.

My initial plan was to cut into the wall behind the valve and just 
replace the entire assembly. Advantage: I know how to do that. 
Disadvantage: yet another distraction.

However, maybe I can use a threaded insert to hold this handle into the 
valve for now. Googling "plastic helicoil" doesn't help much and I don't 
think I know the right vocabulary. Anyone have a suggestion for keeping 
this handle stuck to its valve and functioning as a shower for six 
months or so until its associated bathroom gets gutted anyway?