M20 8.8 Zinc Plated Hexagon Bolts

Product Description

M20 × 2.5mm property class 8.8 zinc-plated steel hexagon-head bolts with a plain shank, manufactured to the traditional DIN 931 / current ISO 4014 part-threaded pattern.

These high-tensile metric bolts feature a conventional external hexagon head, a threaded end and an unthreaded shank beneath the head. The plain shank can provide improved alignment and shear support when correctly positioned through the clearance holes of the joined components.

• Thread size: M20
• Thread pitch: 2.5mm metric coarse
• Threading: Part threaded
• Construction: Threaded end with plain shank
• Available lengths: 60mm, 70mm, 80mm, 90mm, 120mm, 130mm, 160mm and 200mm
• Head style: External hexagon head
• Width across flats: Approximately 30mm
• Recommended spanner or socket size: 30mm
• Head height: Approximately 12.5mm
• Material: High-tensile steel
• Property class: 8.8
• Finish: Zinc plated
• Traditional standard: DIN 931
• Current international standard: ISO 4014
• British adoption: BS EN ISO 4014
• Pack sizes available: 1, 5, 10, 20, 50, 100 and 250

These M20 hexagon-head bolts are suitable for heavy machinery, agricultural equipment, commercial vehicles, structural brackets, steel fabrication, plant maintenance and demanding general engineering assemblies.

The standard M20 × 2.5mm metric coarse thread must be used with a corresponding M20 × 2.5mm nut, threaded insert or tapped hole. It is not interchangeable with M20 metric fine threads such as M20 × 2.0mm or M20 × 1.5mm.

The part-threaded design incorporates a plain shank between the underside of the head and the threaded section. When the correct bolt length is selected, this unthreaded portion can pass through the joined components and provide improved location and shear support compared with a fully threaded set screw.

The approximate plain-shank figures in the table have been calculated by subtracting the stated thread length from the overall under-head bolt length. Manufacturing tolerances and the thread run-out area can affect the exact usable shank length.

When selecting a bolt, ensure that the plain shank passes through the clearance holes without bottoming against the nut or entering too deeply into a tapped hole. Sufficient thread engagement must remain for the intended joint and required clamp load.

Property class 8.8 is a high-tensile steel fastener grade with a nominal tensile strength of approximately 800 N/mm². The second figure indicates a nominal yield-strength ratio of 0.8, giving a nominal yield strength of approximately 640 N/mm².

The bolt should be paired with suitably rated M20 nuts and washers. Correct tightening torque depends on the joint design, lubrication, thread condition, washer arrangement, mating materials and required preload.

The external hexagon head is installed using a correctly fitting 30mm spanner or socket. Ensure the tool is seated fully across the flats before applying torque to reduce the risk of rounding or damaging the head.

The zinc-plated finish provides improved corrosion resistance compared with untreated self-colour steel and is suitable for many indoor and sheltered outdoor applications. It is not normally recommended for prolonged exposure to marine, coastal or highly corrosive environments.

Hexagon bolt length is measured from directly beneath the head to the end of the bolt. The external hexagon head is not included in the stated length.

Please note: DIN 931 is the traditional designation for part-threaded metric hexagon-head bolts. ISO 4014 is the corresponding current international dimensional standard, with BS EN ISO 4014 being the British adoption. Dimensions and specifications are intended as a guide only and may vary within permitted manufacturing tolerances. Check the bolt where shank position, thread engagement, strength or dimensions are critical.

Please Note: Specifications given are intended as a guide only. If critical to your project please check with us first.