Assembly Considerations

• Self-threading screws for joining plastic parts come in two basic varieties: thread-cutting and thread-forming.
  
  
• Thread-cutting screws cut away material from the inner diameter of the boss to form a mating thread. Thread-forming screws do not have a cutting tip but displace material in the plastic boss to create a mating thread.
  
  
• Thread cutting screws produce lesser radial and hoop stresses in the boss than thread-forming screws. They are, therefore, better for long-term performance.
  
  
• Thread-forming screws can be used in multiple assembly/disassembly operations. Thread-cutting screws must be re-installed carefully to avoid damaging the previously cut threads.
  
  
• Because of the high levels of assembly stress, thread-forming screws should not be used with polycarbonate resin or its blends. Thread-cutting screws should be used for these materials.