M2.5 x 0.45p Metric Coarse Stainless A2-70 G304 Button Head Socket (1.5mm Key) Screws ISO 7380

About Button Head Socket Screws

Button Head Socket Screws have a low-profile rounded dome head with a hex socket (Allen key) drive. Lower head profile than a socket cap screw and a softer visual finish than a countersunk, used where the bolt head will be visible but the customer wants minimal protrusion. Lower install torque rating than a socket cap (about 70 to 80 percent at the same diameter), so use for decorative or moderate-load assemblies rather than maximum-clamp joints. Manufactured to ISO 7380 (metric) or ANSI B18.3 (imperial).

Frequently Asked Questions

Material & Coating

Stainless A2-70 G304 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 (Metric) Metric fasteners measure thread pitch as the distance between thread peaks, expressed in millimetres. Metric also branches into three series: coarse (the default; widest tolerance, easiest to tap), fine (a tighter pitch for higher clamp load or thinner walls), and extra fine (the tightest pitch, used for thin-wall tube, precision instruments, and aerospace fittings where vibration loosening must be minimised). Always match the series as well as the size - a metric fine nut will not engage a metric coarse bolt of the same diameter, and an extra fine nut will not engage either. This product has a 0.45mm coarse pitch, meaning the peaks are 0.45mm apart.

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 screw the thread length runs from the start of the unthreaded section (called the shank) to the end of the thread. To view the thread length for this product, 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.