Side-by-Side Comparison
Imperial Threads (UNC/UNF)
1/2"-13 UNC vs. 3/8"-16 UNC
Comparing 2 standards across 7 specifications. 7 key differences identified.
Comparing:
1/2"-13 UNC
3/8"-16 UNC
1/2"-13 UNC is a heavy fractional Unified Coarse bolt thread with a major diameter of 0.5000 inches (12.700 mm) and 13 threads per inch (TPI). Requiring a 27/64 inch (0.4219 inch) tap drill, it is the standard structural fastener for automotive engine cradles, trailer hitches, and building timber connections.
3/8"-16 UNC is a fractional Unified Coarse machine screw thread with a major diameter of 0.3750 inches (9.525 mm) and 16 threads per inch (TPI). Requiring a 5/16 inch (0.3125 inch) tap drill, it is the international standard for professional photography tripod-to-head mounting studs, cinema camera baseplates, and stage microphone stands.
Specification Comparison Table
7 Parameters| Parameter / Spec | ||
|---|---|---|
|
Nominal Major Diameter
|
0.5000 in (12.700 mm) | 0.3750 in (9.525 mm) |
|
Threads Per Inch (TPI)
|
13 TPI (Coarse pitch: 1.954 mm) | 16 TPI (Coarse pitch: 1.588 mm) |
|
Fine Pitch Equivalent
|
1/2"-20 UNF (1.270 mm pitch — standard automotive wheel lugs) | 3/8"-24 UNF (1.058 mm pitch) |
|
Recommended Tap Drill Size
|
27/64 in drill bit (0.4219 in / 10.72 mm) | 5/16 in drill bit (0.3125 in / 7.94 mm) |
|
Minor Diameter (Internal)
|
0.4167 in (10.584 mm) | 0.3073 in (7.805 mm) |
|
Tensile Stress Area
|
0.1419 in² (91.5 mm²) | 0.0775 in² (50.0 mm²) |
|
Common Drive Size
|
3/4" Hex (19.05 mm) / 3/8" Allen | 9/16" Hex (14.28 mm) / 5/16" Allen |