METRIC 12.9 SOCKET HEAD CAP SCREWS (DIN 912) are typically manufactured from alloy carbon steel, quenched and tempered for strength, usually black oxide (plain) finish. They have a minimum tensile strength of 1220 MPa, (M2 to M48) and generally agreed to be the equivalent to Imperial Grade 8 bolts @ 172000 psi.
This series socket head bolt are identified with a "12.9" marking on the head. Coarse threads are most common. Thread length is formulated at 4 x diameter, or fully threaded for shorter lengths less than the formula. Length is measured from under the head.
The number preceeding ".", ie 8.8, 10.9, 12.9 refers to the maximum load that the fastener can handle as a percentage of its ultimate tensile strength, ie: 80 or 90 %. Torquing or loading beyond the safe limit, known as the elastic range causes the fastener to suffer an unrecoverable stretch & deformation resulting in shear or fractional failure.
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Zinc Plate or Fine Thread by special order, ask your rep to confirm availability.