ASME B18.2.1 Hex Bolts DIN M6-M64 1/2"-2 1/2" stainless steel fasteners

1. ASME B18.2.1 Bolts and Screws

ASME B18.2.1 is the standard specification covering the dimensional requirements for nine products types of inch series bolts and screws recognized as American National Standard. All dimensions of bolts and screws conforming to this standard are in inches and apply to unplated and uncoated product. When plating or coating is specified, the finished product dimensions shall be as agreed upon between supplier and purchaser. A bolt is an externally threaded fastener, generally used with a nut. It fits in an over-sized hole and is tightened by an end nut. A screw is also an externally threaded fastener, generally used without a nut. It normally fits in a threaded hole.

2. Construction and Manufacture

Bolts and screws manufactured in accordance with ASME B18.2.1 are all headed fasteners. The terminology “headed” indicates the basic construction style of the fastener, which is a partly or fully threaded rod or shank with a head. The head may be manufactured to various types such as square, hex, hex flange, and lobed, etc. Top of the head shall be full form and chamfered, with the diameter of chamfer circle equal to the maximum width across flats. The head height shall include the thickness of the washer face where provided. Besides, the head may be cross-drilled for self-locking purpose. Generally, the under-head surface and the washer face (if provided) are called bearing surface. As illustrated in Figure-1 and Figure-2, a fillet shall be furnished so that the head-to-shank transition can be more smooth which means low stress concentration.

Figure-1: a typical drawing of headed bolt conforming to ASME B18.2.1

The body style furnished shall be either full size body or reduced body at the discretion of purchaser. The end of the shank shall be pointed (chamfered). The chamfer angle may vary depending on specific manufacturing process. The presence of the pointed end is to reduce the possibility of damage to the leading threads and to promote ease of assembly with a tapped hole or nut. The bolt or screw may be furnished in “full thread” (threaded for full length) or “half thread” (not threaded for full length, partly threaded) construction. The threads shall meet the requirements of ASME B1.1 except that lag screw thread dimensions are otherwise specified. Thread series on the bolts and screws may be coarse (UNC), fine (UNF), or 8 thread series (8 UN), except askew head bolts, which shall be unified coarse (UNC) only, and lag screws, which are otherwise specified.

Figure-2: a typical drawing of headed screw conforming to ASME B18.21.

3. Material

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