Side-by-Side Comparison
Imperial Threads (UNC/UNF)
1/4"-20 UNC vs. #4-40 UNC
Comparing 2 standards across 8 specifications. 8 key differences identified.
Comparing:
1/4"-20 UNC
#4-40 UNC
1/4"-20 UNC is a fractional Unified Coarse machine screw thread with a major diameter of 0.2500 inches (6.350 mm) and 20 threads per inch (TPI). Requiring a #7 (0.2010 inch) tap drill, it is the universal global standard under ISO 1222 for camera tripod mounting sockets, studio light stands, and general machinery bolting.
4-40 UNC is a numbered Unified Coarse machine screw thread with a major diameter of 0.1120 inches (2.845 mm) and 40 threads per inch (TPI). Requiring a #43 (0.0890 inch) tap drill, it is the worldwide computing standard for D-subminiature connector jackscrews (VGA, DVI, RS-232 serial ports).
Specification Comparison Table
8 Parameters| Parameter / Spec | ||
|---|---|---|
|
Nominal Major Diameter
|
0.2500 in (6.350 mm) | 0.1120 in (2.845 mm) |
|
Threads Per Inch (TPI)
|
20 TPI (Coarse pitch: 1.270 mm) | 40 TPI (Coarse pitch: 0.635 mm) |
|
Fine Pitch Equivalent
|
1/4"-28 UNF (0.907 mm pitch) | #4-48 UNF (0.529 mm pitch) |
|
Recommended Tap Drill Size
|
#7 drill bit (0.2010 in / 5.10 mm) or 13/64 in | #43 drill bit (0.0890 in / 2.26 mm) |
|
Minor Diameter (Internal)
|
0.1959 in (4.976 mm) | 0.0849 in (2.156 mm) |
|
Tensile Stress Area
|
0.0318 in² (20.5 mm²) | 0.00604 in² (3.90 mm²) |
|
Common Drive Size
|
7/16" Hex (11.11 mm) / 3/16" Allen (4.76 mm) | — |
|
Common Computing Role
|
— | D-sub / VGA / DVI thumbscrew standoffs |