SEMS Screws

SEMS Screws, by Clarendon Specialty Fasteners are pre-assembled screws with one or two free spinning, captivated washers. This ingenious combination of components offers many benefits which have revolutionised assembly manufacturing processes, particularly in the Aerospace Avionics sector.

1.6mm SEMS screws now available as part of the new micro range!

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Key benefits:

  • Manufactured in the UK by Clarendon Specialty Fasteners
  • UK, European and US sourced material with full traceability.
  • Lot traceable, material certification and FAIR’s available.
  • Reduces Foreign Object Damage (FOD)
  • Reduces component assembly time
  • Reduces inventory count
  • Improves ease and speed of assembly
  • Eliminates downtime due to lost components
  • Lowers kitting part count

Configure your own SEMS by clicking below:

Download Product Guide:

Configuration Options

There are literally millions of permutations of SEMS combinations and our SEMS Configurator will aid you in the selection process. In summary, the following are offered as standard, with bespoke options also available:

Drive Styles

  • Hex Recess
  • Cross Recess
  • Hexalobular
  • Security Drive
  • Custom

Head Styles

  • Cap Head
  • Pan Head
  • Cheese Head
  • PCB Stand-Offs
  • Custom


  • Metric M1.6 to M10
  • Inch 2-56 UNC to ÂĽ-28 UNF


  • 316 Stainless Steel A4-70
  • A286 Stainless Steel
  • Custom


  • Plain
  • Spring
  • Custom


  • Natural
  • Passivated
  • Chemi-Black
  • Custom

Getting the right SEMS for your application is easy. 
Try the SEMS Configurator via the link below or simply select via the SEMS product guide.

Application Areas

SEMS can be used anywhere where a screw and washer(s) are required. SEMS manufactured by Clarendon Specialty Fasteners are made to a very high quality standard, with full traceability and release to AS9100 which tend to be used more so in Aerospace applications. Application examples as follows:

  • Avionic communication systems
  • Flight control systems
  • Electronic engine control systems
  • Electronic warfare and countermeasures
  • Infra-red systems and cameras
  • Missile & ground munition systems
  • Naval & ground fire control systems
  • Display systems
  • Control consoles
  • Battery packs
  • PCB assembly
  • Drone sub assemblies

Case Study - Connector Assembly

In the following example, the use of SEMS in combination with a nut plate can drastically reduce the number of components used in an electrical connector assembly. The total number of fasteners required reduces from 16 to 5, assembly time reduces and the need for multiple tools is eliminated.

Current Assembly – Standard Screw & Washer Configuration:

4 x Screws
8 x Washers
4 x Nuts

16 x Total Fastener Components

  • Multiple loose components
  • Multiple part numbers to order & stock
  • High chance of FOD
  • Time consuming to assemble
  • Multiple tools required

Enhanced Assembly – SEMS Solution:

4 x SEMS
1 x Nut Plate

5 x Total Fastener Components

  • 60% reduction in parts, simplified ordering & stock management
  • Chance of FOD reduced significantly
  • Quick & easy to assemble
  • Only one tool required