Hanger Bolt

What is a Hanger Bolt?

A hanger bolt is a specialized double-ended fastener that is an indispensable component in woodworking, furniture assembly, and construction. It features threads on both ends but with different designs: one end typically has machine screw threads (fine, uniform threads), while the other end features lag screw threads (coarse, tapered threads). The central section is often an unthreaded shank. This unique design allows it to perform a bridging function—the lag thread end is driven into wood or another soft material, creating a strong, permanent anchor. The machine thread end then protrudes, ready to accept a nut or be screwed into a tapped hole in metal or another piece of hardware. This makes the hanger bolt the perfect connector for attaching table legs, leveling feet, chair swivels, and other fixtures to wooden bases.

Detailed Product Specifications & Parameters

Understanding the precise specifications of hanger bolts is crucial for selecting the correct fastener for your project. Our products are manufactured to exacting standards from high-quality materials.

Common Materials and Finishes

• Materials:
  • Steel: Most common, offering good strength and affordability. Often available with various platings.
  • Stainless Steel (18-8 / 304, 316): Excellent corrosion resistance for outdoor, marine, or high-moisture environments.
  • Brass: Good corrosion resistance and aesthetic appeal, often used in decorative applications.
  • Zinc-Plated Steel: A cost-effective finish providing a basic level of rust protection for indoor use.
  • Hot-Dip Galvanized: A thick zinc coating for superior corrosion resistance in demanding outdoor applications.
• Finishes: Zinc plating, clear or yellow chromate, hot-dip galvanizing, plain (unfinished), and brass.

Key Dimensional Parameters

Technical Performance Data

Hanger Bolt FAQs

Q: How do I install a hanger bolt correctly?
A: Correct installation is a two-step process. First, for the lag screw end, drill a pilot hole in the wood. The pilot hole diameter should be slightly smaller than the root diameter (the core) of the lag thread—typically about 70% of the shank diameter for hardwoods and 90% for softwoods. This prevents wood splitting. Second, drive the lag thread into the pilot hole. You can use a special hanger bolt installation tool, a wrench on the square/hex drive (if present), or jam two nuts together on the machine thread end and use a wrench on the outer nut. Drive it until the unthreaded shank is flush with or slightly into the wood surface. The machine thread end will then be protruding, ready for assembly.

Q: Can I use a hanger bolt to join two pieces of metal?
A: No, that is not their intended purpose. The lag screw end is specifically designed to grip into wood or similar fibrous materials. It cannot cut threads into metal. To join two metal pieces, you would use a standard bolt, screw, or a stud that has machine threads on both ends (a double-end stud).

Q: What is the difference between a hanger bolt and a dowel screw?
A: This is a common point of confusion. Both are double-ended fasteners, but they differ in their thread types. A hanger bolt has two different threads: machine screw thread on one end and lag screw thread on the other. A dowel screw has the same type of thread on both ends—typically lag screw threads or a similar coarse wood thread. Dowel screws are used for hidden wood-to-wood joints (like furniture knock-down fittings), while hanger bolts are for wood-to-metal or wood-to-hardware connections.

Q: How do I determine the right size hanger bolt for my project?
A: Follow this sizing guide: 1) Lag Thread Size: Choose based on the thickness and density of the wood. Larger diameters (3/8", 1/2") provide greater pull-out strength for heavy loads. 2) Machine Thread Size: This must match the nut or the tapped hole in the hardware you are attaching (e.g., a table leg plate). Check if it's 1/4"-20, 5/16"-18, etc. 3) Overall Length: Ensure the lag thread length is sufficient to penetrate at least 2/3 of the wood's thickness for a secure hold. The machine thread length must be long enough to fully engage the nut plus allow for a washer.

Q: Are there left-handed thread hanger bolts?
A: Standard hanger bolts have right-hand threads on both ends (turn clockwise to tighten). Left-handed thread hanger bolts are extremely rare and are custom-made for specific applications where rotation during operation might loosen a right-hand thread. For 99% of applications, the standard right-hand thread is what you need.

Q: What are the most common applications for hanger bolts?
A: Hanger bolts are ubiquitous in furniture and fixture manufacturing. Key applications include: Attaching table and desk legs using a threaded insert or plate; Securing leveling glides and feet to furniture bases; Mounting chair swivel mechanisms to wooden seats or bases; Fastening machinery and equipment to wooden floors or skids; General wood-to-metal connections in cabinetry, railings, and architectural millwork.

Q: How do I prevent a hanger bolt from loosening over time in wood?
A: Several methods enhance security: 1) Proper Pilot Hole: As mentioned, the correct pilot hole size is critical for maximum thread engagement and grip. 2) Adhesive: Applying a small amount of wood glue or thread-locking adhesive (like those used for metal) to the lag threads before installation can bond them to the wood. 3) Mechanical Locking on Machine End: Once assembled, use a lock washer (split or tooth) or a nylon-insert lock nut (nyloc nut) on the machine thread end to prevent vibration from loosening the connection.

Q: Can hanger bolts be removed and reused?
A: Removal is possible but can be difficult and may damage the wood or the fastener. To remove, you must unscrew the lag thread end from the wood, which requires gripping the machine thread end (if accessible) or using locking pliers on the shank. The extraction process often strips the wood fibers, reducing holding power for reinstallation. It is generally recommended to treat hanger bolt installations as semi-permanent; if disassembly is frequently required, consider alternative fastening systems like threaded inserts in the wood.