I'm trying to figure out the screw size to the Spyderco Karahawk's ring screw size. Do I need to buy one of those sizing charts or is there some trick to measure screw size without it? I can but screws in 0-80,1-72,2-56,4-40 etc. but know for sure it isn't a 4-40. I measure and do calculations but nothing matches up with what niph khits dat cam has. I plan to buy a chart with my screw purchase because this keeps happening with Spydercos. For now is there anything I can do with simple tools at home?