Machine Screw - Size Chart

Tap Drill Size: Use this drill bit when you plan to cut (tap) threads into the hole. The tap drill leaves just enough material for the threads to engage properly.
Clearance Drill Size: Use this drill bit when the screw must pass through freely without threading — such as through the top board in a two-piece wood joint, or through a bracket.
UNC (Coarse Thread): Unified National Coarse. Standard for most general applications. Faster to install, better in softer materials, more resistant to cross-threading.
UNF (Fine Thread): Unified National Fine. Used where greater strength, better vibration resistance, or finer adjustment is needed.
— indicates no fine-thread option is available for that size.