A2-70 grade stainless steel - also known as grade 304 or 18/8. A general purpose grade of stainless steel. A4-70 grade stainless steel - also known as grade 316 or 18/8/3. A higher corrosion resistant, marine grade of stainless steel.

Thread galling mainly occurs with fasteners made of aluminium, titanium, stainless steel, and other alloys which self-generate an oxide surface film for corrosion protection.

Rural Environments A2 Stainless Steel (Type 304) performs well on exposed surfaces although slight discolouration may occur on sheltered surfaces.

The two most commonly produced grades of stainless steel are 304 (known as 'A2') and 316 (known as A4). Both of these grades will offer excellent corrosion resistance, cleanability, and the ability to handle extremely low (cryogenic) and high temperatures.

Stainless steel is principally known and considered for use because of its high level of corrosion resistance in both wet and dry conditions, particularly in comparison with standard carbon steels.

A2 - The most commonly produced grade of stainless steel. Also known as grade or type 304.A4 - The second most commonly produced grade of stainless steel. Also known as grade or type 316.A/F - A shortened form of 'width across flats'.Acorn Nut - Another name for a dome nut.Allen Key - A tool with a hexagonal cross section used for tightening up screws with a socket head.Allthread - A metal bar that has a thread all along its length.

The following table describes the strength specifications for the different property classes of metric steel bolts, screws and studs:

The following table lists the most popularly used threaded fasteners used today, and the DIN standard or otherwise to which they have been designed:

Threaded Fasteners - An Overview of Thread Standards Standardisation of screw thread forms is an ongoing process begun in the 19th century.

Standard: ASTM A325/Din933 hex bolts Dia.: 1/2""-1 1/2""; Length:1 1/4""-8""; Surface treatment: Plain ,Black oxygenation, HDG Scope The ASTM A325 specification covers high strength heavy hex structural bolts from ½” diameter through 1-1/2” diameter. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts. Refer to the Structural Bolts page of our site for thread lengths and other related dimensions.

The American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services.

The ASTM A153 specification covers zinc coating (hot-dip) on iron and steel hardware. A newer and more appropriate specification developed in 2005 covering the requirement for hot-dip galvanizing of bolts, screws, nuts, washers and other threaded fasteners

Originally approved in 1936, this specification is heavily utilized in petroleum and chemical construction applications. The ASTM standard covers alloy steel and stainless steel bolting materials for high temperature service.

The ASTM A194 specification covers carbon, alloy and stainless steel nuts intended for use in high-pressure and/or high-temperature service. Unless otherwise specified, the American National Standard Heavy Hex Series

Originally approved in 1948, the ASTM A320 specification covers alloy steel and stainless steel bolting materials for low temperature service. This standard covers rolled, forged, or strain hardened bars, bolts, screws, studs, and stud bolts used for pressure vessels, valves, flanges, and fittings. Like the ASTM A193 specification, unless otherwise specified, the 8UN thread series is specified on fastener larger than 1” in diameter.