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  • Unification. Bold type indicates products unified dimensionally with British and Canadian standards. Unification of fine thread nuts is limited to sizes 1 in. and smaller.
  • Tops and Bearing Surfaces of Nuts. Nuts in sizes 5/8 in. nominal size and smaller shall be double chamfered. Larger size nuts shall be double chamfered or have washer faced bearing surface and chamfered top.
    The diameter of chamfer circle on double chamfered nuts and diameter of washer face shall be within the limits of the
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Unit of Measure

Manufacturer

Manufacturer

Industrial Fasteners Institute

Specifications

Product

Nuts

Unit of Measure

English

Nominal Size or Basic Major Dia. of Thread

5/16 in

Nominal Size or Basic Major Dia. of Thread (Decimal)

0.3125 in

Basic Width Across Flats (F)

1/2 in

Max. Width Across Flats (F)

0.500 in

Min. Width Across Flats (F)

0.489 in

Max. Width Across Corners (G)

0.577 in

Min. Width Across Corners (G)

0.557 in

Basic Thickness (H)

17/64 in

Max. Thickness (H)

0.273 in

Min. Thickness (H)

0.258 in

Codes and Standards

Codes and Standards

ASME/ANSI B18.2.2 1987 (R 1999)

Runout of Bearing Face, FIM

Max. Runout of Bearing Face, FIM (Specified Proof Load Up to 150,000 psi)

0.016 in

Max. Runout of Bearing Face, FIM (Specified Proof Load 150,000 psi and Greater)

0.011 in