UNC & UNF Bolts & Set Screws

What are UNF Threads and UNC Threads?

UNF and UNC are two systems of Unified Screw Thread Series, which defined based on the number of threads per inch and standardised width gauge, these two thread systems share the fact that they are both measured in imperial units. UNF threads are Unified fine pitch threads, while UNC threads are Unified coarse pitch threads. UNF and UNC thread screws are both used for fastening, but mainly applied in different fields. coarse thread has higher strength and find thread is better for sealing.

Difference Between UNF and UNC Thread

When it is used as fasteners, the preloads of UNF and UNC threads are close. The effect of preventing loosening of fine thread is better than that of coarse thread. When it is used for adjustment, fine thread has more advantages. More difference between UNF thread and UNC thread are as following:

1) The UNF threads have smaller helix angle and better tightness, and it is more conducive to the self-locking of the thread. Therefore, it’s not as easy to loosen compared with UNC threads. It is generally used for thin-walled parts and parts with higher anti vibration requirement.

2)The UNF threads have smaller pitch, there are more teeth per screw in the same thread length, it can reduce fluid leakage, so it is used in the applications where sealing is needed.

3)The UNC thread has less teeth of the same length, larger cross-section size of each tooth, and are more suitable for bearing larger tensile force and impact force.

4)Compared with fine thread, coarse thread has higher strength and good interchangeability.

5) UNC thread also greater tolerances, handles manufacturing and plating better than UNF threading.

6)Due to the varying characteristics, Unified coarse screw thread and unified fine screw thread have different uses.

Our Yeovil Branch is stocked with UNF and UNC bolts and set screws, we would also be able to help you identify any bolt that you are not 100% sure of the exact thread type.

We are also able to order special items that may not be listed here, please call or Whats'app 01935 432744 or email, sales@wentinfasteners.co.uk