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This calculator may be used to compute recommended fastener spacing.


  • Enter values for Y: width of cover edge and t: thickness of cover plate
    (Refer to the drawings and variables as described in Fastener Spacing)
  • Select the cover plate material and Spira gasket from a drop-down list.
  • Standard values will be filled in automatically. Enter custom values as desired.

The calculator solves for L: length between fasteners and F0: the force the fastener must exert on the gasket. The calculator automatically updates when any value is changed.

Note: We multiply by 80% as a safety factor.

Width of Cover Edge (Y): (inches)
Modulus of Elasticity of Cover Plate (E):     Cover Plate Material:

Thickness of Cover Edge (t): (inches)

(Delta) Deflection of Gasket (d): (inches)

Diameter of Spiral (D): (inches)      
Minimum force of gasket on cover (F1): (pounds per inch)     Spira Part #
Maximum force of gasket on cover (F2): (pounds per inch)      

Length Between Fasteners (L):   inches

Force fastener must exert to compress gasket 25% of its diameter (F0):   pounds