M20 Bolts

M20 Bolts — Heavy Structural and Industrial Fasteners for Maximum Load

M20 bolts are one of the largest standard metric bolt sizes in regular industrial and construction use in Australia, delivering the clamping force required for primary structural connections, heavy machinery mounts, large civil anchors, and high-load applications across engineering and construction. With a 20 mm nominal diameter and standard coarse pitch of 2.5 mm, M20 is a primary bolt size under AS 4100 (Steel Structures) and the standard specification for heavy-duty anchor bolts in concrete foundations. AIMS Industrial stocks M20 bolts in Grade 8.8 and structural grades, stainless steel, and galvanised from Sydney.

Types of M20 Bolts

M20 hex head bolts (AS 1111.1 / ISO 4014/4017, 30 mm across flats) are driven with a 30 mm spanner or socket and are the standard for structural steel connections and heavy mechanical applications. M20 structural bolts per AS/NZS 1252 are high-strength bolts for fully-tensioned structural connections — they must be used with matching AS/NZS 1252 nuts and hardened washers. M20 socket cap screws (ISO 4762, 17 mm hex key) are used in heavy machine building, press tooling, and hydraulic systems. M20 anchor bolts are the most commonly specified size for column bases and heavy machinery foundation anchors in Australian construction — supplied as cast-in L-bolts, J-bolts, threaded rod with plate, sleeve anchors, or chemset (chemical anchor) assemblies. M20 chemset/chemical anchor rods with epoxy or polyester resin are used for post-installed anchor applications in structural concrete. M20 eye bolts provide heavy-duty lifting and rigging attachment points.

Grades and Materials

Grade 8.8 M20 hex bolts (800 MPa tensile, 640 MPa yield, zinc-plated) are the standard commercial specification for mechanical applications. AS/NZS 1252 Grade 8.8S structural bolts are the correct specification for fully-tensioned structural steel connections per AS 4100 — do not substitute commercial Grade 8.8 unless the design permits snug-tight installation. Grade 4.6 M20 bolts are used for cast-in anchor bolt applications where ductility is more important than strength. Grade 10.9 M20 is available for high-strength clamping and heavy machinery applications. M20 stainless steel bolts in A4-80 (316 stainless) are used in marine, coastal, and aggressive chemical environments. Hot-dip galvanised M20 bolts per AS/NZS 4680 are the standard for exposed structural applications, bridges, and outdoor infrastructure.

Thread Specifications and Dimensions

M20 coarse pitch: 2.5 mm; fine pitch M20×1.5 is available for specific applications. Hex head across-flats: 30 mm. Socket cap screw hex drive: 17 mm. Standard stock lengths: 30 mm to 500 mm for hex bolts. Anchor bolt lengths are project-specific — embedment depth must be determined from design calculations or the anchor manufacturer's technical data. Tightening torque for Grade 8.8 M20 (dry): approximately 430 N·m; structural bolt installation per AS 4100 requires calibrated methods. Always confirm torque requirements with the design specification.

Applications

M20 bolts are the backbone fastener in primary structural steel connections — portal frames, braced bays, moment connections, column splices, and heavy gusset plates in industrial buildings, bridges, and infrastructure. In civil and construction, M20 anchor bolts are specified for every major column base plate, machinery foundation, and structural post. Mining and resource sector plant relies heavily on M20 bolts in crusher frames, conveyor head frames, mill housings, and heavy screens. Heavy transport (truck bodies, trailers, tank mounting) and major agricultural machinery (harvester headers, rock crushers, bale handlers) also use M20 as a primary connection bolt. M20 chemset anchor rods are the dominant product for post-installed structural anchors in concrete where higher loads or edge conditions rule out mechanical anchors.

Selecting the Right M20 Bolt

Confirm the installation method first: snug-tight or fully-tensioned structural applications require AS/NZS 1252 compliant bolts and a specific tightening procedure per AS 4100. For mechanical or non-structural applications, Grade 8.8 commercial hex bolts are appropriate. For anchor bolt applications, the structural engineer must specify anchor type, embedment, edge distances, and design loads — never select a concrete anchor without verified load data. For outdoor or marine service, hot-dip galvanised or A4 stainless steel is essential. Pair M20 bolts with the correct full nut (ISO 4032 or heavy hex nut) and plain washer (ISO 7089-2 or hardened washer for structural connections).

AIMS Industrial supplies M20 bolts in Grade 8.8 commercial, AS/NZS 1252 structural, Grade 4.6 anchor bolt, Grade 10.9, 316 stainless steel, and hot-dip galvanised in a range of lengths. Contact our Sydney team for trade and project pricing, and Australia-wide delivery.