This unique Sems fastener features an integral, free-spinning, Cone washer. With two distinct configurations, this dual action spring washer has two separate load deflection rates. The configurations act in unison to provide a reliable low torque, controlled tension fastener.

The Cone Sems assembly provides a higher retained clamp load and improved compensation for thermal cycling and vibration. This fastener is capable of accepting a high tension load while maintaining a live spring action and generates a constant load, even with variations in installation torques. By increasing the acceptable driving torque range it enhances flexibility in component design.

The Cone washer's long deflection period and two-stage loading contribute to better control during installation, improved tool bit life and reduced operator fatigue. (See Fig.1) Load is directed towards the outer diameter of the washer, making the fastener ideal for clamping fragile materials and for spanning large clearance holes.

Cone SEMS Assemblies A = Across Flats
B1 = Across Corners
B2 = Pan Head O.D.
C1 = Hex Head Height
C2 = Pan Head Height
D = Washer Diameter
H = Overall Washer Height
T = Washer Material Thickness
E = Slot Width
F = Slot Depth
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