The Experts: SEMS overview

Q:  What are SEMS?

A: SEMS are a bolt combination with a permanently attached washer or set of washers. It is also referred to as captivated washers, screw/bolt-washer assemblies or combi bolts. The word SEMS originates from The Illinois Tool Works Inc., who made machines that produced pre-asSEMbled washers and screws. In spite of the original patents and trademarks, the word SEMS is generally recognised as a generic term applicable to screw and washer assemblies. The washers are installed on the bolt blank before thread rolling. Since the outer diameter of the threads becomes larger than the inner diameter of the washers, the washers are prevented from prising loose from the bolt. It is normally possible for the washer/washers to slide on the non-threaded part of the bolt.

SEMS offers several benefits in terms of faster or easier assembly and handling. The Nord-Lock combi bolts, which are relatively new within our product range, combine the convenience of a bolt with a pre-assembled Nord-Lock washer pair for superior locking capacity.

The Nord-Lock combi bolt offers the following:

  • Ensures faster product assembly, thanks to pre-assembled and pre-lubricated parts.
  • Decreases failures relating to improper mounting or failing to attach washers.
  • Facilitates product assembly in the case of extremely small dimensions.
  • Makes service and repair in rough surroundings or hard-to-reach areas easier and safer.
  • Facilitates inventory and logistics, thanks to having fewer item numbers.
  • Makes disassembly faster and easier, as loose washers can be hard to remove, especially from tapped holes.
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