5/16" x 18 TPI UNC Coarse Stainless A4-70 G316 Hex Bolts ASNI B18.2.1

About Hex Bolts & Set Screws

Hex Bolts and Set Screws are the workhorses of the bolting world. The default fastener whenever you need to clamp two parts together with a spanner on both ends. Six-sided head driven with a spanner or socket, and a fully or partially threaded shank. A hex bolt is partially threaded (plain shank under the head); a hex set screw is fully threaded right up to the head. Used for metal-to-metal joints, machinery assembly, structural framing, and any application that needs reliable clamp load.

Frequently Asked Questions

Material & Coating

Stainless A4-70 G316 Austenitic stainless steel. Property class 70 designates a minimum tensile strength of 700 MPa with a 0.2 percent proof stress of 450 MPa. Lightly magnetic in cold-worked form, which does not affect corrosion performance.

Grade selection A2-70 G304 is the general-purpose stainless grade for outdoor and most chemical environments. A4-70 G316 contains 2 to 3 percent molybdenum, giving substantially better resistance to chlorides; A4-70 G316 is the preferred grade for marine, coastal and pool environments.

Important Do not pair stainless fasteners with plain or galvanised steel components in wet service. The galvanic potential difference accelerates corrosion of the less-noble metal.

Class Stainless fasteners are classified by property class: A2-35 / A2-50 / A2-70 in G304 stainless, and A4-40 / A4-70 / A4-80 (Bumax 88) in G316. The first digit indicates the alloy and the second is the minimum tensile strength in 100 MPa increments (e.g. A4-70 = 700 MPa). See the head marking chart and full strength table.

Thread Pitch & Terminology

Thread Pitch (Imperial) Imperial fasteners measure thread pitch as TPI (threads per inch), the number of thread peaks per inch of fastener length. Imperial systems include UNC (coarse), UNF (fine), BSW (Whitworth) and BSF (British Standard Fine). This product has 18 TPI, meaning 18 thread peaks per inch.

How to Measure

Fastener Length This product has a head that sits on top of the material, so the length is measured from directly under the head to the tip of the thread. The head itself is not included in the size.

Thread Length On a bolt the thread length runs from the start of the unthreaded section (called the shank) to the end of the thread. Set screws are fully threaded. If the length is 75mm, the thread length is 75mm. To view the thread length, select a length above.

Resources

Pricing & Delivery

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Disclaimer

Technical data Researched and compiled from numerous industry sources for the sole purpose of providing basic information. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person, and Bolt and Nut Australia is not responsible for any loss, claim or damages arising therefrom. In developing this information, Bolt and Nut Australia has made a determined effort to present it accurately.

Measurements Sizes are taken from supplier catalogues or hand-measured and should be used as a guide. Minor variation between batches is normal. Stock is sourced from various suppliers, so differences may exist between batches in thread length, markings, appearance or finish.

Product Photos & PDF Data Sheets Represent the product type, not exact size. PDFs are a reference guide only. Specifications may change without notice.

If you see any problems with any of our specifications or you require additional information please contact us.