The Hanger Bolt (also known as a “Wood to Metal Dowel” or “Dual Thread Screw”) is a headless fastener designed to connect metal fixtures to wooden structures. Featuring a unique dual-ended design, the Hanger Bolt has a coarse lag thread on one end for biting into timber rafters, and a standard unified or metric machine thread on the other end to accept a nut. This makes it the industry standard for installing solar racking systems, suspending electrical conduits, and assembling furniture legs.
Product Overview: Manufactured from ductile C1008 Carbon Steel and finished with a bright Zinc Plating, our Hanger Bolts offer excellent holding power and basic corrosion resistance. Whether you are mounting solar L-feet to a residential roof or manufacturing high-end tables, these bolts provide a secure, concealed connection point.
Hanger Bolt Specifications
| Product Name | Hanger Bolt / Dowel Screw / Solar Hanger Screw |
| Material Grade | C1008 Carbon Steel (Standard) / Stainless Steel Available |
| Surface Treatment | Zinc Plated (Blue/White) for rust protection |
| Thread Type A | Wood / Lag Thread (Self-Tapping) |
| Thread Type B | Machine Thread (Metric M6-M12 or UNC) |
Engineering Insight: How to Install a Headless Bolt?
Since the Hanger Bolt has no head for a wrench, installing it can be tricky. Professionals use one of two methods:
- The Double Nut Method (Most Common): Thread two Hex Nuts onto the machine-thread end. Tighten the two nuts against each other (lock them). Now, put your wrench on the outer nut and turn. The locked nuts will transfer the torque, driving the lag end into the wood. Once installed, unlock and remove the nuts.
- Hanger Bolt Driver: For high-volume solar installations, use a specialized “Hanger Bolt Driver” bit for your power drill. This tool grips the machine threads internally without damaging them.
For more details on screw drive types, please refer to the Screw drive entry on Wikipedia.
Applications
- Solar Mounting: The #1 choice for attaching aluminum rails to wooden roof trusses. Usually paired with an L-Foot and EPDM washer.
- Furniture Manufacturing: Attaching legs to sofas and tables. The machine thread allows the leg to be easily assembled and disassembled by the end-user.
- Suspension: Hanging pipes or false ceilings from wooden beams.
Frequently Asked Questions (FAQ)
Q: Do I need to pre-drill the wood?
A: Yes. Hanger bolts are thick. If you drive them directly into a beam without a pilot hole, you risk splitting the wood. Drill a pilot hole slightly smaller than the lag thread diameter.
Q: Can I use C1008 steel outdoors?
A: Zinc Plated C1008 is fine for furniture or dry environments. For outdoor solar roofing, we strongly recommend upgrading to our Stainless Steel 304 Hanger Bolts to prevent rust over 20 years.
Need Solar Hanger Bolts?
Handan Bolt manufactures millions of Hanger Bolts (M8, M10, M12). We can supply them pre-assembled with nuts and EPDM washers for solar kits.
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