4UN and 4UNR Fixed Pitch Series Thread Chart

Measured in Inches
Size Primary
Inch
Basic Major Diameter
Inch
Basic Pitch Diameter
Inch
Minor Diameter, inch Minor Dia. Area
sq. inch
Tensile Stress Area
sq. inch
External Thread Internal Thread
2-1/2 2.5 2.3376 2.2023 2.2294 3.72 4
2-5/8 2.625 2.4626 2.3273 2.3544 4.16 4.45
2-3/4 2.75 2.5876 2.4523 2.4794 4.62 4.93
2-7/8 2.875 2.7126 2.5773 2.6044 5.11 5.44
3 3 2.8376 2.7023 2.7294 5.62 5.97
3-1/8 3.125 2.9626 2.8273 2.8544 6.16 6.52
3-1/4 3.25 3.0876 2.9523 2.9794 6.72 7.1
3-3/8 3.375 3.2126 3.0773 3.1044 7.31 7.7
3-1/2 3.5 3.3376 3.2023 3.2294 7.92 8.33
3-5/8 3.625 3.4626 3.3273 3.3544 8.55 9
3-3/4 3.75 3.5876 3.4523 3.4794 9.21 9.66
3-7/8 3.875 3.7126 3.5773 3.6044 9.9 10.36
4 4 3.8376 3.7023 3.7294 10.61 11.08
4-1/8 4.125 3.9626 3.8273 3.8544 11.34 11.83
4-3/8 4.375 4.2126 4.0773 4.1044 12.88 13.41
4-1/2 4.5 4.3376 4.2023 4.2294 13.69 14.23
4-5/8 4.625 4.4626 4.3273 4.3544 14.52 15.1
4-3/4 4.75 4.5876 4.4523 4.4794 15.4 15.9
4-7/8 4.875 4.7126 4.5773 4.6044 16.3 16.8
5 5 4.8376 4.7023 4.7294 17.2 17.8
5-1/8 5.125 4.9626 4.8273 4.8544 18.1 18.7
5-1/4 5.25 5.0876 4.9523 4.9794 19.1 19.7
5-3/8 5.375 5.2126 5.0773 5.1044 20 20.7
5-1/2 5.5 5.3376 5.2023 5.2294 21 21.7
5-5/8 5.625 5.4626 5.3273 5.3544 22.1 22.7
5-3/4 5.75 5.5876 5.4523 5.4794 23.1 23.8
5-7/8 5.875 5.7126 5.5773 5.6044 24.2 24.9
6 6 5.8376 5.7023 5.7294 25.3 26