What is the difference between BSF/BSW and UNF/UNC?
author: Bertha
2024-06-03
Both of these thread types are used for imperial thread.
BSF and BSW are British measurement systems, while UNF and UNC are American measurement systems.
BSF and UNF are the fine thread systems, while BSW and UNC are the coarse thread systems.
BSF and BSW are British measurement systems, while UNF and UNC are American measurement systems.
BSF and UNF are the fine thread systems, while BSW and UNC are the coarse thread systems.
The difference between BSF/BSW and UNF/UNC is dual:
- The thread angle:
The BSF/BSW have a thread angle of 55°
BSF-BSW thread angle
The UNF/UNC have a thread angle of 60°
UNF-UNC thread angle
- The thread profile:
The BSF/BSW have a wave like thread profile
BSF-BSW thread profile
The UNF/UNC have theorically a flattend crest and root in the thread profile, however to aid the manufacturing proces they are slightly rounded inside a maximum outline.
UNF-UNC theoretical thread profile
UNF-UNC practical thread profile
Be aware that although they look similar, they should not be used as full replacements or be mixed with each other!
- UNF and BSF have completly different thread per inch value. So they don't fit.
- UNC and BSW have the same thread per inch value, accept for the 1/2" size. Theoretical it would be possible to interchange them as they have the same amount of threads per inch. However due to the difference in thread angle, the connection would not be as strong as when using the proper combinations.
Chipboard Screw
Wedge Anchor
