ASTM A962, behind A193, A194 and A320, says what is marked and where: the grade symbol and the maker's identification on one end of studs 3/8 in. (10 mm) and larger, on bolt heads 1/4 in. (6 mm) and larger, and on every nut, never on a bearing face. It does not say how, so a legible laser mark meets it; specifications that want depressed marks need a mark with depth, such as dot peen.
On stainless steel the heat of the mark matters: laser colouring can lower the corrosion resistance of some stainless steels. Where corrosion at the mark matters, the method is agreed first: dot peen, or laser marking followed by outside passivation.
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model dataWhere the marks go: ASTM A962 (studs 3/8 in. and larger on one end, bolt heads 1/4 in. and larger, never the bearing surface, every nut) and ASTM A194 (one face of the nut, not the wrench flats). How the beam is steered and the kinds of laser mark: NASA-HDBK-6003C. Stainless steel: NASA-HDBK-6003C and published salt-spray and pitting studies of laser-marked 304L and implant stainless. The stud is drawn as a 1-1/4-8 UN B7 stud and the bolt and nut to 1 in. heavy hex proportions (ASME B18.2.1 and B18.2.2). The maker's mark is INF, marked above the grade symbol with the heat code below (on a nut face the three are equally spaced round it), and H-24A117 is an example heat. The near-infrared beam is invisible in life and is drawn faint; the lens-to-part distance is illustrative and no depth is shown for the mark. The marker, enclosure, laser source, controller, fixture, test report and mill certificate are generic, and the documents show no results. The marking is slowed down, and the marked end is shown enlarged.
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