WHAT THREAD? UNC, UNF, BSF, BSW
How to measure the thread
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
Standard
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.
Fine
Otherwise known as UNEF Unified National Extra Fine.
UNEF (Unified Extra Fine) is the same as UNF except that the number of threads per inch is even higher for each fastener size.
Imperial TPI’s (Threads per inch)
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 |