Views: 0 Author: Site Editor Publish Time: 2026-10-21 Origin: Site
Joining heavy wood members (beams, joists, and posts) with standard hex bolts presents operational challenges:
Single-Tool Installation: Standard hex bolts require two wrenches (one holding the head, one turning the nut). A carriage bolt self-locks into the wood, allowing a single worker to torque the nut from the access side.
Tamper-Resistant Security: The smooth, rounded dome head provides no external drive recess or wrench flats, preventing unauthorized removal from the exposed exterior face.
Safety & Aesthetics: The absence of sharp hex corners makes carriage bolts standard in playground structures, pedestrian boardwalks, public park benches, and guardrails.
┌─────────────────────────┐ ( Smooth Domed Head ) <--- No drive recess / tamper-resistant └───────────┬─────────────┘ │ [Square Neck] <--- Embeds into wood grain or square steel slot │ [Rolled Round Shank] <--- Through-hole clearance section │ [Precision Thread] <--- Clamped via washer and standard hex nut
Domed Head Geometry: The low-profile convex head deflects tampering tools and provides a clean architectural finish.
Square Neck (Anti-Spin Feature): As the bolt is drawn into the wood by tightening the nut, the square profile cuts into the perimeter of the round pilot hole, creating an anti-rotation lock that prevents the bolt from spinning under assembly torque.
Load Clamping Mechanics: The bolt shank acts in tension, pulling the connected members into tight contact.
| Nominal Diameter | Standard Length Range | Core Material Grades | Recommended Surface Finish | Primary Application Sector |
|---|---|---|---|---|
| M6 / M8 | 20mm – 120mm | Low Carbon Steel / Stainless Steel | Electro-Galvanized (Clear/Yellow Zinc) | Residential wooden fencing, timber furniture, garden pergolas |
| M10 / M12 | 40mm – 200mm | Medium Carbon Steel (Grade 4.8 / 8.8) | Hot-Dip Galvanized (HDG ≥45μm) | Structural timber framing, wooden bridge decking, highway guardrails |
| M16 / M20 | 80mm – 300mm+ | Quenched & Tempered Carbon Steel | Hot-Dip Galvanized / Dacromet | Heavy marine timber wharves, mining timber supports, civil structures |
Answer: Spinning occurs if the pre-drilled pilot hole is oversized, or if the bolt is forced into deteriorated wood. The pilot hole diameter should match the nominal thread diameter of the bolt—never the width of the square neck. The square neck should be firmly tapped into the wood with a mallet prior to tightening the nut.
Answer: No washer is placed under the domed head, as the square neck must embed directly into the timber. However, a heavy flat washer or square plate washer must always be installed under the nut on the opposite side to distribute clamping pressure and prevent the nut from sinking into the wood fibers.
Donghuang Hardware produces metric and imperial carriage bolts conforming to international standards (such as DIN 603 / ISO 8677) with batch traceability and custom packaging.
Product Catalog: Explore bolt selections at dh-hardware.com/Bolt-pl47711397.html.
Direct Inquiries: Contact tony@wf-fastener.com / Phone: +86-13355841616.
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