• Surface Condition. Bolts need not be finished on any surface except threads.
  • Top of Head. Top of head shall be full form and chamfered with the diameter of chamfer circle being equal to the maximum width across flats, within a tolerance of minus 15 percent.
  • Head Taper. Maximum width across flats and across corners shall not be exceeded. No transverse section through the head between 25 percent and 75 percent of actual head height, as measured from the bearing surface, shall be less than the minimum width across flats and across corners.
  • Bearing Surface. A die seam across the bearing surface is permissible. Bearing surface shall be perpendicular to the axis of the body within a tolerance of 3 deg for 1 in. size and smaller, and 2 deg for sizes larger than 1 in. Angularity measurement shall be taken at a location to avoid interference from a die seam. Special bearing surface finishes may be provided as agreed between purchaser and manufacturer.
  • True Position of Head. The axis of the head shall be located at true position with respect to the axis of the body (determined over a distance under the head equal to one diameter) within a tolerance zone having a diameter equivalent to 6 percent of the maximum width across flats, regardless of feature size.
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Unit of Measure
Items
Rolled Thread Square Bolts

Square Bolt, 1/4" Nominal Dia.
Rolled Thread Square Bolts

Square Bolt, 5/16" Nominal Dia.
Rolled Thread Square Bolts

Square Bolt, 3/8" Nominal Dia.
Rolled Thread Square Bolts

Square Bolt, 7/16" Nominal Dia.
Rolled Thread Square Bolts

Square Bolt, 1/2" Nominal Dia.
Manufacturer N/A Industrial Fasteners Institute
Product N/A Square and Hex Bolts and Screws
Codes and Standards N/A ASME B18.2.1 1996
Unit of Measure N/A English
Nominal Size or Basic Product Diameter N/A 1/4 in N/A 5/16 in N/A 3/8 in N/A 7/16 in N/A 1/2 in
Nominal Size or Basic Product Diameter (Decimal) N/A 0.2500 in N/A 0.3125 in N/A 0.3750 in N/A 0.4375 in N/A 0.5000 in
Max. Full-Size Body Diameter (E) N/A 0.260 in N/A 0.324 in N/A 0.388 in N/A 0.452 in N/A 0.515 in
Min. Full-Size Body Diameter (E) N/A 0.237 in N/A 0.298 in N/A 0.360 in N/A 0.421 in N/A 0.482 in
Basic Width Across Flats (F) N/A 3/8 in N/A 1/2 in N/A 9/16 in N/A 5/8 in N/A 3/4 in
Max. Width Across Flats (F) N/A 0.375 in N/A 0.500 in N/A 0.562 in N/A 0.625 in N/A 0.750 in
Min. Width Across Flats (F) N/A 0.362 in N/A 0.484 in N/A 0.544 in N/A 0.603 in N/A 0.725 in
Max. Width Across Corners (G) N/A 0.530 in N/A 0.707 in N/A 0.795 in N/A 0.884 in N/A 1.061 in
Min. Width Across Corners (G) N/A 0.498 in N/A 0.665 in N/A 0.747 in N/A 0.828 in N/A 0.995 in
Basic Head Height (H) N/A 11/64 in N/A 13/64 in N/A 1/4 in N/A 19/64 in N/A 21/64 in
Max. Head Height (H) N/A 0.188 in N/A 0.220 in N/A 0.268 in N/A 0.316 in N/A 0.348 in
Min. Head Height (H) N/A 0.156 in N/A 0.186 in N/A 0.232 in N/A 0.278 in N/A 0.308 in
Max. Radius of Fillet (R) N/A 0.03 in
Min. Radius of Fillet (R) N/A 0.010 in
Nom. LT for Bolt Length (6 in. and Shorter) N/A 0.750 in N/A 0.875 in N/A 1.000 in N/A 1.125 in N/A 1.250 in
Nom. LT for Bolt Length (Over 6 in.) N/A 1.000 in N/A 1.125 in N/A 1.250 in N/A 1.375 in N/A 1.500 in
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