IMPERIAL

Imperial mild steel round washers are flat, low-carbon steel washers sized in fractional inches to accompany traditional imperial thread forms like UNC, UNF, BSW (Whitworth), and BSF.

These are categorised according to BS 3410 where washers are divided into specific tables that govern their dimensional scope and intended utility:

  • Table 3 (Light & Heavy Series): The standard "everyday" imperial engineering washer, functionally tracking like a metric Form A or Form B. They are optimized for general shop floor mechanics and light-to-medium clamp loads.
  • Table 4 (Light & Heavy Series): Features tightly constrained outer edge radii. These are specified strictly for compact, narrow clearance housings where the washer must sit tucked closely against a flange or step.
  • Table 7 Series: Explicitly designated as "Regular Sized Black Washers" with wide tolerances. They are manufactured with significantly more generous hole clearances and heavier thickness profiles to support structural engineering, civil layout projects, and heavy equipment assemblies.
IMPERIAL
TABLE 3

TABLE 3
TABLE 4

TABLE 4
TABLE 7

TABLE 7