ASME B18.5 (T2):2012 Inch Series Round Head Square Neck Bolt is a carriage-bolt style fastener with a smooth round head and a square neck that can seat into wood or plate holes to prevent rotation during tightening.
It is suitable for wood structures, guardrails, agricultural equipment, vehicle bodies, brackets, and assemblies that benefit from one-side tightening. The rounded exposed head improves safety, while the square neck increases installation convenience and anti-rotation performance.
Square-neck size, hole form, grip thickness, and thread length should be matched carefully. For outdoor wood structures or vehicle environments, zinc plating, hot-dip galvanizing, or other protective finishes can improve durability.

Dimensions unit: inch
|
Thread size d |
10# |
1/4 |
5/16 |
3/8 |
7/16 |
1/2 |
5/8 |
3/4 |
7/8 |
1 |
|
|
d |
0.1900 |
0.2500 |
0.3125 |
0.3750 |
0.4375 |
0.5000 |
0.6250 |
0.7500 |
0.8750 |
1.0000 |
|
|
PP |
UNC |
24 |
20 |
18 |
16 |
14 |
13 |
11 |
10 |
9 |
8 |
|
ds |
Max. |
0.199 |
0.260 |
0.324 |
0.388 |
0.452 |
0.515 |
0.642 |
0.768 |
0.895 |
1.022 |
|
Min. |
0.159 |
0.213 |
0.272 |
0.329 |
0.385 |
0.444 |
0.559 |
0.678 |
0.795 |
0.910 |
|
|
dk |
Max. |
0.469 |
0.594 |
0.719 |
0.844 |
0.969 |
1.094 |
1.344 |
1.594 |
1.844 |
2.094 |
|
Min. |
0.436 |
0.563 |
0.688 |
0.782 |
0.907 |
1.032 |
1.219 |
1.469 |
1.719 |
1.969 |
|
|
k |
Max. |
0.114 |
0.145 |
0.176 |
0.208 |
0.239 |
0.270 |
0.344 |
0.406 |
0.459 |
0.531 |
|
Min. |
0.094 |
0.125 |
0.156 |
0.188 |
0.219 |
0.250 |
0.313 |
0.375 |
0.438 |
0.500 |
|
|
s |
Max. |
0.199 |
0.260 |
0.324 |
0.388 |
0.452 |
0.515 |
0.642 |
0.768 |
0.895 |
1.022 |
|
Min. |
0.185 |
0.245 |
0.307 |
0.368 |
0.431 |
0.492 |
0.616 |
0.741 |
0.865 |
0.990 |
|
|
k1 |
Max. |
0.125 |
0.156 |
0.187 |
0.219 |
0.250 |
0.281 |
0.344 |
0.406 |
0.469 |
0.531 |
|
Min. |
0.094 |
0.125 |
0.156 |
0.188 |
0.219 |
0.250 |
0.313 |
0.375 |
0.438 |
0.500 |
|
|
r |
0.031 |
0.031 |
0.031 |
0.047 |
0.047 |
0.047 |
0.078 |
0.078 |
0.094 |
0.094 |
|
|
R |
0.031 |
0.031 |
0.031 |
0.031 |
0.031 |
0.031 |
0.062 |
0.062 |
0.062 |
0.062 |
|
ABOUT US
Better Fastener is a professional fastener enterprise specializing in the manufacturing of steel washers, stainless steel washers, spring washers and sealingwashers. Founded in 2001 as a washer factory, the company expanded into a comprehensive enterprise integrating washers, nuts, bolts, spring nuts and other fastener products in 2010.
The company positions itself as a provider of comprehensive one-stop services for customers, relying on technological R&D, industrial investment and trade distribution.
With an experienced professional team and a sound sales network, Better Fastener has achieved excellent sales performance in both domestic and foreign markets,and has grown into one of the competitive manufacturers and suppliers in China's industrial fastener industry.
Better Fastener is committed to becoming a trusted fastener supplier for customers with reliable product quality, reasonable prices and on-time delivery
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