Imperial Threads
7 indexed entriesPart of Tools & Home Improvement.
Items
1/2"-13 UNC
1/2"-13 UNC has a major diameter of 0.500 inches (12.7mm) with 13 threads per inch, tapped with a 27/64-inch drill. It's the smallest diameter covered by the ASTM A325/A490 structural bolt specifications used in steel building construction, and a common size for heavy-duty lag screws and general fasteners.
1/4-20 UNC
A 1/4"-20 UNC bolt has a major diameter of 0.250 inches (6.35 mm) with 20 threads per inch. The standard tap drill size is a #7 drill (0.2010 in / 5.11 mm). It is the universal standard thread for photography tripod mounts.
#10-24 UNC
#10-24 UNC has a major diameter of 0.190 inches (4.83mm) with 24 threads per inch, tapped with a #25 drill. It's the largest of the Unified numbered-gauge sizes, sitting directly below 1/4-20, and a common general-purpose machine screw used in electrical work, hardware assembly, and light machinery.
3/8-16 UNC
A 3/8"-16 UNC bolt has a 0.375 inch (9.525 mm) major diameter and 16 threads per inch. Tap drill size is 5/16 in (0.3125 in / 7.94 mm) using a 9/16" socket. It is the heavy-duty standard for cinema tripod heads and stage rigging.
5/16"-18 UNC
5/16"-18 UNC has a major diameter of 0.3125 inches (7.94mm) with 18 threads per inch, tapped with an F-size drill. It's a widely used general-purpose size in North American automotive, machinery, and structural hardware, sitting between #10-24 and 3/8-16 in the Unified coarse-thread series.
#6-32 UNC
#6-32 UNC has a major diameter of 0.138 inches (3.51mm) with 32 threads per inch. The standard tap drill is a #36 bit. It's the standard screw for desktop PC cases -- power supplies, expansion cards, and drive bays -- and for US electrical wall plates and outlet/switch mounting.
#8-32 UNC
#8-32 UNC has a major diameter of 0.164 inches (4.17mm) with 32 threads per inch, tapped with a #29 drill. It's a common size for circuit-board standoffs and general electronics hardware, and one of the two thread sizes -- alongside 10-32 -- used for the green grounding screw on US electrical devices.