The Hex Lag Screw (manufactured to DIN 571 standards) is the premier fastener for heavy timber construction. Often referred to in the trade as a “Coach Screw,” this Hex Lag Screw combines the biting power of a wood thread with the high-torque capability of a hexagonal head, making it indispensable for securing deck posts, railway sleepers, and timber frames.
Product Overview: Unlike standard screws, our Hex Lag Screw is cold-forged from premium Stainless Steel A2 (304) or A4 (316). Choosing a stainless Hex Lag Screw ensures your outdoor structures remain safe and rust-free for decades, even in harsh coastal environments.
Hex Lag Screw Specifications (DIN 571)
| Product Name | Hex Lag Screw / Coach Screw |
| Standard | DIN 571 (Metric) |
| Material Grade | Stainless Steel A2 (304) / A4 (316) |
| Head Style | Hexagon Head |
| Application | Heavy Duty Timber Connections |
Engineering Insight: Hex Lag Screw Design
Why do engineers specify the Hex Lag Screw for structural loads? It comes down to the “Partial Thread” design:
- Clamping Force: The unthreaded shank of the Hex Lag Screw allows the top piece of timber to be pulled tightly against the bottom piece. A fully threaded screw would merely bridge the gap.
- Shear Strength: The solid shank of a Hex Lag Screw offers superior resistance to shear forces (sideways pressure) compared to thinner wood screws.
Hex Lag Screw Installation Guide
To install a Hex Lag Screw correctly, pre-drilling is mandatory. Attempting to drive a large diameter Hex Lag Screw without a pilot hole can split the wood.
- Softwood: Drill 70% of the shank diameter.
- Hardwood: Drill 90% of the shank diameter.
Material Guide: A2 vs A4
- A2 (304): Standard stainless for garden structures.
- A4 (316): Marine grade for docks and piers.
Frequently Asked Questions (FAQ)
Q: What is the difference between a lag bolt and a hex lag screw?
A: They are the same product. “Hex Lag Screw” is the technical term (because it has threads), but “Lag Bolt” is the common site name due to its hex head.
Q: Do I need a washer with a Hex Lag Screw?
A: Yes, use a DIN 9021 (Wide Flat Washer) to prevent the head from sinking into the timber.
Need Bulk Hex Lag Screws?
Handan Bolt is a leading manufacturer of the Hex Lag Screw in both metric and imperial sizes. Contact us for factory direct pricing.
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