They are a BS 2470:1973. The technical data for the material is that it is high tensile grade alloy steel, heat treated to RC39-43. The material has a
Thread Spec: BSW 1/8 5/32 3/16 1/4 5/16. Socket Cap Head Screw Allen Bolts Hex Drive. Drive Style: Hex Drive. Material: Carbon Steel (High
BSW 1/8 5/32 3/16 1/4 5/16Hex Socket Cap Screw High Tensile 12.9 Allen Bolt
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Whitworth High Tensile Socket Grub Screws 3/16 1/4 5/16 3/8
5/16 3/8 1/2 BSW Whitworth capuchon haute traction tête boulons vis à douille EUR 5,47 - PicClick FR
Lawson-HIS FBOI0280 [CL] High Tensile Hex-Head Whitworth Bolt 7/16BSW x 1.1/4 from Lawson HIS
UNC 1/4 Socket Cap Screw High Tensile 12.9 Self Colour DIN912 – Fixaball Ltd. Fixings and Fasteners UK
10 3/8 x 1 1/2 WHITWORTH COACH BOLTS with square nuts £7.49 - PicClick UK
Everbilt 3/8 in.-16 x 2-1/2 in. Hex Socket Head Stainless Steel Socket Cap Screw 825458 - The Home Depot
5/16 BSW Whitworth Hex Set High Tensile R/ 8.8 Self-Colour DIN933 – Fixaball Ltd. Fixings and Fasteners UK
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