Chamfering Stud Ends in 3D

The first thread is where the nut starts, or doesn't

A saw cut leaves a burr and a ragged thread start that make a nut hard to start straight. Chamfering to below the root removes both, so the nut meets a clean, full thread first.

It is a requirement, not a nicety. ASTM A962, which A193, A194 and A320 call up, has studs and bolts pointed, flat and chamfered or rounded, with the point one to two complete threads long. ASME B18.31.2 sets the chamfered length, U, for every stud size: 0.125 to 0.250 in. on a 1 in.-8 stud. A rounded end may be used instead of a chamfer at the maker's choice; the one-to-two-thread rule still applies.

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Points flat and chamfered or rounded, one to two complete threads long, and stud length measured from first thread to first thread: ASTM A962 and A193. Chamfered thread distance U, 0.125–0.250 in. on 1 in.-8, judged by how far a NOT GO major-diameter ring goes on, with the chamfer from the major diameter to the root or below and the end square and fit for marking: ASME B18.31.2. The 45° chamfer: precision machining design guidance. Grade and maker's symbols on one end of studs 3/8 in. and larger: ASTM A962. The stud is drawn as a 1 in.-8 UNC-2A stud and the nut to ASME B18.2.2 heavy hex proportions. The chamfering machine is drawn generic after the shop's own stud chamfering machine: the stud clamped against a stop rod through the spindle in an air-operated split vise (a cylinder sized to the stud, split down the middle, opening left and right), a cutter head with carbide inserts fed onto the end along linear rails, the cutting area enclosed over a chip drawer, the stud turned end for end by hand. The ring gauge and the marker are generic; the marks are drawn as the shop lays them out, INF (the maker's mark) over the grade, B7, over the heat number, here an example, H-24A117. The burrs are drawn larger than life, the enclosure and the head are drawn see-through, and the cuts and the marking are slowed down.