I'm trying to convert old "razor only" receptacles to GFCI protected ones in bathrooms. Since the old outlets are large 2-gang 4" boxes, I had to get GFCI conversion kits (manufacturer's specs) with a 2-gang, 1 centered receptacle support plate and wall plate:
The problem: the holes where the new GFCI receptacle should screw in (the small circles in the support plate at the right in the image above) are untapped.
It is extremely difficult to screw in the receptacle's screws into those holes. The hole size seems about right, matching the shaft diameter of the screw without the threads. A 7/64" drill bit slides smoothly in the hole.
The receptacle's screws are tapered at the tips and they can get the threading started, but it gets stuck quickly. I tried using the old receptacle's screws to continue the threading and it is so difficult that the screw head broke. I also found another switch with what appear to be self-tapping screws of the same thickness and threading, and they can't even get started.
I unfortunately don't have taps. I also thought of drilling the holes a bit larger, but the next drill bit size seems to be 1/8" which looks too big.
Am I missing something? I would think this must be a standardized part that is meant for simple installation without so much difficulty or additional steps such as thread tapping. For example, this how-to guide.