Double-Headed Bolts: A Comprehensive Guide
Introduction
A double-headed bolt (also called a double-ended stud, double-head screw, or dowel screw) is a cylindrical fastener with threads on both ends and an unthreaded (smooth) center section . These bolts are designed to connect two components simultaneously and are indispensable in applications requiring strong, reliable, and often hidden joints .
Key Features
Dual Threading: Threads can be identical or different (e.g., machine screw on one end and wood screw on the other) to suit varied materials .
Smooth Center Shaft: The unthreaded mid-section provides structural integrity and precise spacing .
Materials & Strength: Common materials include carbon steel (e.g., Q235, 45#), alloy steel (e.g., 35CrMoA), and stainless steel (e.g., 304, 316) . High-strength variants (B7, B16, etc.) are used for extreme conditions .
Applications
Double-headed bolts are widely used in:
Heavy Machinery & Structures: Mining equipment, bridges, cranes, boiler steel frames, and large-span steel buildings .
Automotive & Energy: Reducer frames, valves, petroleum refining, and railway systems .
Furniture & Construction: End-to-end joints, baluster attachment, and monorail beam suspensions .
Installation Guidelines
Preparation: Use lubricants to ease installation and prevent seizing .
Pilot Holes: Predrill holes to match the bolt diameter; hardwood may require slightly larger holes .
Alignment: Ensure the bolt axis is perpendicular to the surface; use a square to verify .
Torque Control: Tighten with calibrated tools to avoid over-torquing, which may compromise joint integrity .
Surface Treatments
To enhance durability and corrosion resistance, double-headed bolts undergo treatments such as electroplating, blackening, phosphating, or non-electrolytic zinc flake coating .
Standards & Customization
Manufactured to standards like GB897-GB901, these bolts range from M3 to M100 in diameter, with customizable lengths . Special orders can include heat-treated grades for high-temperature or high-pressure environments .
Conclusion
Double-headed bolts offer a robust solution for demanding mechanical and structural connections. Their versatility, strength, and adaptability make them essential in industries ranging from construction to energy. Proper selection, installation, and maintenance ensure long-term reliability in critical applications.
