Hex Socket Head Cap Screw M8x40 8.8 — Dedra SI-M8X40/KL-8.8

Dedra SI-M8X40/KL-8.8 is a hex socket head cap screw M8x40 with a strength class of 8.8, designed for mechanical assembly, metal construction and equipment fastening. The screw features a cylindrical head with an internal hex drive for torque transfer using an Allen key or hex bit. Its medium-high tensile strength and standardized metric thread make it suitable for secure clamping in machinery, automotive repairs and industrial installations where reliable joint integrity is required.

Advantages

The hex socket head allows compact installation in confined spaces while providing accurate tightening control. Strength class 8.8 ensures a balance between tensile strength and toughness for durable joints under moderate to high loads. Metric M8 thread and 40 mm length make the fastener compatible with common nuts and tapped holes, supporting straightforward replacement and interchangeability in repair and assembly tasks.

Suitable for

• Assembling machinery frames and metal structures
• Fastening components in automotive maintenance and repairs
• Industrial equipment installation and service
• General mechanical repairs and retrofit work

Key specifications

• Size: M8 × 40 mm
• Head type: hex socket (Allen) cylindrical head
• Strength class: 8.8 (medium-high tensile strength)
• Thread type: metric coarse thread
• Drive: internal hex socket compatible with Allen keys and hex bits

How to use

Select a matching nut or a threaded hole with compatible M8 metric thread depth suitable for the 40 mm length. Insert the screw through the parts to be joined, engage the nut or thread, and tighten using the correctly sized Allen key or hex bit. Apply torque gradually and evenly to achieve the recommended preload for the application; avoid over-tightening to prevent thread or fastener damage. Where applicable, use threadlocker or a spring washer to prevent loosening under vibration.

Usage recommendations

Use the screw in applications compatible with strength class 8.8; for corrosive environments select appropriate surface protection or stainless alternatives. Ensure the Allen key fits the internal hex precisely to avoid stripping the head, and verify thread engagement length to maintain joint safety.