Knowledge base

Stud bolts: threaded studs for ASME flanges

Fully threaded, two heavy hex nuts, material grade to ASTM

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Term explained

Fully threaded, two heavy hex nuts, material grade to ASTM

A stud bolt is a threaded bar with a continuous thread over its entire length that makes up a flanged joint together with two nuts. It has no head; both ends are identical and usually chamfered. Stud bolts are the standard fastener for pipe flanges to ASME B16.5 and B16.47, and for valves, heat exchangers and pressure vessels in the chemical, petrochemical, oil and gas industries and in power plants. In German enquiries they are often called Stehbolzen. The stud bolt differs from the stud to DIN 938 and DIN 939 in its continuous thread and its two nuts; the stud has a metal end and a nut end.

3.2 inspection certificate with studs

What defines a stud bolt

  • Thread: Usually UNC or, from 1 inch, 8UN with eight threads per inch; tolerance class 2A, as UNR with a rounded root. Metric stud bolts are equally common.
  • Length: To ASME B18.31.2, measured end to end excluding the chamfers; the flange standard specifies the length for each nominal size and pressure class.
  • Material grade: To ASTM A193 B7 for general service, B16 for higher temperatures, B8 and B8M in stainless steel; for low temperatures, L7 to ASTM A320. The nuts follow ASTM A194: 2H, 4, 7, 8.
  • Coating: Often manganese phosphate with PTFE anti-friction coating or zinc flake, so that the bolted joint stays free-running during assembly and disassembly outdoors or in a seawater environment.
  • Marking: Grade and manufacturer’s mark on both end faces; the nut carries its grade marking.

How RS Randack manufactures stud bolts

From European raw material of the appropriate grade, quenched and tempered and tested in our own laboratory, threads rolled, marking stamped, nuts from our own nut machining, 3.1 or 3.2 inspection certificate for studs and nuts. Coated stud bolts are rolled so that they remain within gauge after coating. Small batch sizes, special lengths and rush orders for shutdowns and overhauls are our daily business, as are bolts to drawing with special threads.

What you should specify

Diameter with thread series and class, length, material grade of stud and nut, coating, certificate type, quantity and delivery date.

Enquire about stud bolts with nuts and certificates

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