During my engine rebuild, I found that the hole in my charcoal canister mount is "stripped".
The factory sheetmetal screw no longer bites in the hole:


Hence I have decided to drill (don't know how large yet) out these holes and use U-nuts instead.
I picked up this package from Canadian Tire:

They have a spring-loaded tang.

I want to know what is the proper hole diameter (in the panel) for use with U-nuts of this style.

I am presently imagining two possible hole sizes, which I have named A and B:


A:
Large enough to allow the screw to pass through, but the tang does not fall into the hole. The tang maintains a constant squeeze on the panel.

B:
Large enough for the tang to snap into the hole... this kind of "clips" the U-nut into place, making it semi-captive.

Which of these methods is the correct one?

B
The tang keeps the u-nut from falling out.
~ Paul
aka "Tha Driver"

Custom Fiberglass Parts

I did "B" and it seems to work OK. I just need to paint the exposed metal now.

Thanks.

Another solution would be to drill and install a thread insert

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

I do have a rivnut tool and the rivnuts to go with it...

That said, if the threads of the screw rust and fuse to the rivnut, then when trying to unscrew the screw, the rivnut could simply spin in the panel.

Hence, where possible, I prefer U-nuts to rivnuts.

Cheap fix, a pair of vice grips to squeeze the stripped hole back to usable size. Kind of a one-time shot, as the metal is weaker after stripping, but I had an armrest mount that stripped and kept dropping the big, long bolt out onto my carpet and rendering the armrest shaky. I got frustrated and pinched the hole with vice grips and it has held up for a year now. Works on these crude applications, it seems.