Fastener Wikipedi-Difference Between Metric and Imperial Threads-ZJB Fastener

 

What is the difference between metric thread and Imperial Thread ?

 

Express :

 

The biggest difference is metric expressed by thread pitch, imperial expressed by thread count.

Such us  :

• Metric: M6-1.0  means diameter M 6 pitch is 1.0mm.
• Imperial:1/4-20 means there are 20 pcs threads in one inch .

 

Angle of thread:

 

The angle is different from Metric and Imperial Threads 

Metric Thread : 60 degree .

Imperial Thread

• UNC :60 degree.
• BSW :55 degree
• 

• Sutiablity of Fastener

   

  In theory:

  Metric Bolt with Metric Nut   

  BSW Bolt with BSW nut

  UNC Bolt with UNC nut 

   

  In practice:

  sometimes for general-purpose bolt and nut , the unc bolt can suit with bsw nut , except 1/2 size, beacause there are very very little different between them . so you can't exact judge the nut whether is UNC or BSW thread by using UNC bolt.

  What should we judge which thread it is ? using the thread gage or More precise measuring instruments.

   

  Related:

   

  What is BSW Thread

   

  What is Metric Thread