I don't know the proper names of these parts so bear with me. I'm reconfiguring my bathroom and I'm still using the old cast iron tub. I'm trying to put on the overflow drain but I'm having an issue connecting it. there's the decorative cover that the machine screw goes through into the pvc fitting with the fat rubber washer in between. I can't seem to get the screw to bite the threads. Like, I'm on the back pushing the pvc and washer as hard as I can against the tub to compress the rubber and my dad is on the other side trying to get the screw in. seems like the screw is too short but this is part of a home depot drain kit. is my old giant tub wall too thick? Or am I just doing something wrong?

YOu probably either need a longer bolt, or it is the wrong diameter. Try it into the overflow without the plate to see if it the correct size.

yeah it fits the female threads. Guess its just too short. Odd because I figured a kit would accommodate all tub sizes

get a longer screw. make sure it is stainless or brass.
make sure that the 6 o-clock part of the washer lines up perfectly with the 6 o-clock area of the hole in the tub.

Some kits send two bolts, a long one and a short one, apparently yours did not.