How to Calculate Thread Length on a Bolt
At Arun Fasteners we are often asked about the thread length on differing size Hex Head Bolts. Below is a helpful guide. NOTE: It is
The pitch is the distance from the crest of one thread to the next in mm. TPI (Threads per inch) is used by inch thread
Otherwise known as UNC Unified National Coarse
standard threads (coarse thread)
UNC meaning Unified Coarse, is the most dominant used in the USA. Often used in the agricultural industry because of their strong coarse threads. Generally available in steel and stainless steel. Come in higher grades – high tensile and higher grades available.
Otherwise known as UNF Unified National Fine.
The pitch is the distance from the crest of one thread to the next in mm. TPI (Threads per inch) is used by inch thread
| SIZE | UNC | BSF | UNF | WHIT/BSW | SIZE | UNC | BSF | UNF | WHIT/BSW |
| 3/16” | 32 | 24 | 1 1/8” | 7 | 9 | 12 | 7 | ||
| ¼” | 20 | 26 | 28 | 20 | 1 ¼” | 7 | 9 | 12 | 7 |
| 5/16” | 18 | 22 | 24 | 18 | 1 3/8” | 6 | 8 | 6 | |
| 3/8” | 16 | 20 | 24 | 16 | 1 ½” | 6 | 8 | 12 | 6 |
| 7/16” | 14 | 18 | 20 | 14 | 1 ¾” | 5 | 7 | 5 | |
| ½” | 13 | 16 | 20 | 12 | 2” | 4 ½ | 7 | 4 ½ | |
| 9/16” | 12 | 16 | 18 | 12 | 2 ¼” | 4 ½ | 6 | 4 | |
| 5/8” | 11 | 14 | 18 | 11 | 2 ½” | 4 | 6 | 4 | |
| ¾” | 10 | 12 | 16 | 10 | 2 ¾” | 4 | 3 ½ | ||
| 7/8” | 9 | 11 | 14 | 9 | 3” | 4 | 3 ½ | ||
| 1” | 8 | 10 | 12 | 8 |
At Arun Fasteners we are often asked about the thread length on differing size Hex Head Bolts. Below is a helpful guide. NOTE: It is
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