The Experts: SEMS overview

What are SEMS?

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.

Nord-Lock design and produce customized wedge-locking washers that are fully compatible with SEMS (pre-assembled bolt-and-washer) applications. If you have any questions or specific needs, please reach out to your local Nord-Lock sales office for guidance.

For customers working with smaller volumes or looking for a flexible alternative, Nord-Lock offers a gluing solution that temporarily secures the washer to the bolt. This provides easy handling, supports efficient assembly, and helps you maintain fast production flow. Our gluing option is available for sizes M6 to M27, up to 150 mm in bolt length, and in standard materials.

Do you have a question about bolt securing? Put the Nord-Lock experts to the test. Email your questions about bolt securing to: experts@nord-lock.com