NEWS

For metric hex bolts (ISO 4014/4017), the two dimensions you need are across-flats width (W) — the wrench size — and head height (k). An M8 bolt has a 13 mm wrench size and 5.3 mm head height; an M10 has 16 mm and 6.4 mm; an M12 has 18 mm and 7.5 mm. Diameter is the thread diameter (M8 = 8 mm thread), and length is measured from under the head to the end of the thread, not including the head.

Choose stainless steel (304/316) when corrosion resistance is the priority — outdoor, marine, chemical, or humid environments — even though it costs 3–6 times more than galvanized. Choose galvanized (zinc-coated carbon steel) when you need high strength at low cost in moderate environments — indoor, dry, or mild outdoor use — because carbon steel grades (8.8/10.9) are far stronger than standard stainless (A2-70 ≈ 5.8 class). If the application is outdoor industrial or near the coast and strength matters, consider hot-dip galvanized high-strength bolts as the middle ground.

The short answer: For a dry (plain, unlubricated) metric bolt, use approximately 10 Nm for M6, 25 Nm for M8, 49 Nm for M10, 85 Nm for M12, 210 Nm for M16, 410 Nm for M20 (grade 8.8, friction coefficient K = 0.2). For grade 10.9, multiply these values by roughly 1.4. Always verify torque against your specific application, lubrication state, and the relevant engineering standard — the table below gives reference values that cover most general structural and mechanical uses.

Choosing the correct Tek screw sizes requires understanding drill point capacity, screw gauge, thread pitch, length, and material thickness. This guide compares Tek 1, Tek 2, Tek 3, Tek 4, and Tek 5 points to explain where each type performs best, from thin sheet metal to heavy structural steel. It also covers grip range, flute clearance, head styles, load requirements, corrosion resistance, and common installation mistakes. By matching the Tek point and screw dimensions to the application, contractors and engineers can prevent drilling failures, thread binding, damaged fasteners, and weak connections.

This guide explains how to choose self drilling screw sizes for different metal thicknesses and structural applications. It covers screw diameter, thread pitch, grip range, overall length, Total Material Thickness (TMT), and Tek point drilling capacities from Tek 2 to Tek 5. The article also compares carbon steel, stainless steel, bi-metal fasteners, and protective coatings for different environments. By correctly matching drill point capacity, thread design, material, and installation speed to the application, engineers and contractors can prevent drill point burnout, thread stripping, joint separation, and premature fastener failure.