The SEMS preassembled screw and washer is another ITW Shakeproof Industrial invention.

We offer many combinations of tooth lock washers, helical spring lock washers, and conical washers preassembled to SEMS machine screw fasteners, thread forming, thread cutting, and self-drilling screws. For your specific SEMS screw preassembled needs, please contact us at

SEMS External Tooth

SEMS – External Tooth Lock-Washer:

  • For use when the surface area can be marred
  • Absorbs assembly torque
SEMS Helical

SEMS – Helical Lock Washer:

  • Meets ASTM specifications
  • Provides resistance to loosening
  • Available in all lock-washer styles
SEMS Dished

SEMS – Dished:

  • Allows for more force on soft or thin materials
  • Internal teeth lock into the bolt to prevent back off
  • Helps prevent damage to the surface area
SEMS Conical

SEMS – Conical:

  • Doesn’t disturb the surface area
  • Adds spring tension to the joint
  • Distributes load over a wider area
SEMS Square Cone

SEMS – Square Cone®:

This innovative Square Cone washer SEMS fastener system includes a free-spinning, integrated Square Cone washer. This dual action spring washer includes two separate configurations and two distinct load deflection rates. Operating in unison, these configurations provide a dependable, controlled-tension, low-torque fastener. Square Cone SEMS screw and washer assemblies supply a higher retained clamp load and enhanced compensation for vibration and thermal cycling. These SEMS fasteners can absorb high tension load while sustaining live spring action, and producing a continual load, regardless of installation torque variations. With an increase in the permissible driving torque range, it component design flexibility.

The Square Cone washer has two-stage loading and long deflection period that add to enhanced control during installation, reduced operation fatigue, and enhanced tool bit life. The load is channeled to the outside diameter of the washer, making the SEMS screw with square washer excellent for clamping delicate materials and spanning large clearance holes.