Side-by-Side Comparison
Imperial Threads (UNC/UNF)
1/4"-20 UNC vs. #8-32 UNC
Comparing 2 standards across 7 specifications. 7 key differences identified.
Comparing:
1/4"-20 UNC
#8-32 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.
8-32 UNC is a numbered Unified Coarse machine screw thread with a major diameter of 0.1640 inches (4.166 mm) and 32 threads per inch (TPI). Requiring a #29 (0.1360 inch) tap drill, it is the standard fastener for North American electrical ceiling junction boxes, light fixtures, and kitchen cabinet hardware knobs.
Specification Comparison Table
7 Parameters| Parameter / Spec | ||
|---|---|---|
|
Nominal Major Diameter
|
0.2500 in (6.350 mm) | 0.1640 in (4.166 mm) |
|
Threads Per Inch (TPI)
|
20 TPI (Coarse pitch: 1.270 mm) | 32 TPI (Coarse pitch: 0.794 mm) |
|
Fine Pitch Equivalent
|
1/4"-28 UNF (0.907 mm pitch) | #8-36 UNF (0.706 mm pitch) |
|
Recommended Tap Drill Size
|
#7 drill bit (0.2010 in / 5.10 mm) or 13/64 in | #29 drill bit (0.1360 in / 3.45 mm) |
|
Minor Diameter (Internal)
|
0.1959 in (4.976 mm) | 0.1302 in (3.307 mm) |
|
Tensile Stress Area
|
0.0318 in² (20.5 mm²) | 0.0140 in² (9.03 mm²) |
|
Common Drive Size
|
7/16" Hex (11.11 mm) / 3/16" Allen (4.76 mm) | PH2 / Slotted / Square #2 |