Machine Screw 2-56 x 1/2" p-ph-s
This is the small phillips panhead screw used to secure most playfield microswitches. The screw has a captive internal tooth lockwasher attached to the head.
Commonly used on many 1990's Bally and Williams games.
Reference:
Basic diameters and threads of Standard SAE numeric system small machine screws are shown below.
The diameters of machine screws are indicated with the number of threads per inch count.
Here is a list of common sizes in inches:
2-56: 0.0860" or 43/500" in diameter; 56 threads per inch
4-40: 0.1120" or 14/125" in diameter; 40 threads per inch
5-40: 0.1250" or 1/8" in diameter; 40 threads per inch
6-32: 0.1380" or 69/500" in diameter; 32 threads per inch
8-32: 0.1640" or 41/250" in diameter; 32 threads per inch
10-32: 0.1900" or 19/100" in diameter; 32 threads per inch
10-24: 0.1900" or 19/100" in diameter; 24 threads per inch
12-24: 0.2160" or 27/125" in diameter; 24 threads per inch