Hanger Bolts: Complete Guide
Types, Sizes, Installation Methods & Applications for Wood-to-Metal Connections
Hanger Bolt Types
Standard, reversed, and heavy-duty configurations
Sizes & Threads
Complete sizing chart with thread specifications
Installation Guide
Proper techniques and required tools
Applications
Common uses and project examples
Downloadable Reference Guides
Quick access to all hanger bolt specification charts and guides
What Are Hanger Bolts?
Hanger bolts (also called dowel screws or stud bolts) are unique dual-threaded fasteners featuring wood screw threads on one end and machine threads on the other. This hybrid design allows for permanent installation into wood while providing a threaded stud for attaching metal hardware, fixtures, or creating adjustable connections.
The wood screw end bites securely into wood grain, while the machine thread end accepts nuts, threaded hardware, or coupling components. Hanger bolts are essential for furniture assembly, fixture mounting, equipment installation, and any application requiring a strong wood-to-metal connection.
Key Advantages of Hanger Bolts
Permanent wood anchoring: The wood screw end provides secure hold without backing out like a traditional bolt would in wood.
Versatile attachment: Machine threads accept any compatible nut, washer, or threaded component for flexible connections.
Load distribution: Transfers loads from metal hardware into wood structure effectively.
Adjustability: Allows for height adjustment and easy assembly/disassembly when using nuts.
Hanger Bolt Types and Configurations
Standard Hanger Bolts
Wood screw threads on one half, machine threads on the other half. Most common configuration for general applications.
- Lag screw thread on wood end
- UNC machine thread on bolt end
- Equal or near-equal thread lengths
- Available in zinc, galvanized, stainless
- Most versatile option
Reversed Hanger Bolts
Machine threads on one end with wood screw threads starting mid-shaft, allowing deeper wood penetration.
- Machine thread section extends further
- Wood threads closer to center
- Greater adjustability above wood surface
- Used when more stud length needed
- Ideal for thick hardware or multiple nuts
Heavy-Duty Hanger Bolts
Thicker diameter and coarser threads for high-load applications requiring maximum holding strength.
- Larger diameters (5/8" to 3/4")
- Coarse wood screw threads
- Grade 5 or higher steel
- Structural hanging applications
- Equipment mounting
Dowel Screws (Double-Ended)
Wood screw threads on both ends without a machine thread section - for wood-to-wood connections.
- Coarse wood threads both ends
- No machine thread section
- Joins two pieces of wood
- Furniture knockdown hardware
- Not a true hanger bolt but related
Stainless Steel Hanger Bolts
Corrosion-resistant option for outdoor, marine, or high-moisture applications.
- 304 or 316 stainless construction
- Excellent corrosion resistance
- Marine and outdoor use
- Food service equipment
- Higher cost, lower availability
Hot-Dip Galvanized
Thick zinc coating provides superior outdoor protection for deck, fence, and exterior applications.
- Heavy zinc coating
- Superior outdoor protection
- Deck and fence construction
- Playground equipment
- More affordable than stainless
Need Help Selecting Hanger Bolts?
Our fastener experts can help you choose the right size, configuration, and finish for your specific application.
Call (866) 573-0445 Browse All Hanger BoltsUnderstanding Hanger Bolt Threads
Wood Screw End (Lag Thread)
The wood screw portion features coarse, aggressive threads designed to cut into wood fibers and create strong holding power:
- Coarse pitch: Wide spacing between threads for wood fiber grip
- Gimlet point: Sharp tapered point for initial wood penetration
- Deep threads: Significant thread depth for maximum holding strength
- Untapered shank: Provides consistent diameter throughout threaded section
Machine Thread End (UNC)
The machine thread end follows standard UNC (Unified National Coarse) specifications:
- Standard pitch: Compatible with standard hex nuts and threaded hardware
- Precision threads: Clean, consistent thread profile
- Full diameter: Threads go to full nominal diameter
- Class 2A tolerance: Standard free-fitting tolerance for easy assembly
Thread Length Considerations
Wood thread length: Should penetrate deep enough for holding power but not through the wood piece. Typically 50-75% of the hanger bolt length.
Machine thread length: Must provide enough projection for hardware thickness plus nut engagement (minimum 1.5 times the diameter).
Example: For a 4" hanger bolt, approximately 2" wood threads and 2" machine threads is typical.
Hanger Bolt Size Chart
Hanger bolts are specified by diameter and total length. Common sizes range from 1/4" to 5/8" diameter in lengths from 2" to 8".
| Diameter | Machine Thread (TPI) | Common Lengths | Wood Thread Length | Machine Thread Length | Pilot Hole Size |
|---|---|---|---|---|---|
| 1/4" | 20 TPI (1/4"-20) | 2", 2-1/2", 3", 4" | 1" - 2" | 1" - 2" | 3/16" (0.1875") |
| 5/16" | 18 TPI (5/16"-18) | 2-1/2", 3", 4", 5" | 1-1/4" - 2-1/2" | 1-1/4" - 2-1/2" | 1/4" (0.250") |
| 3/8" | 16 TPI (3/8"-16) | 3", 4", 5", 6" | 1-1/2" - 3" | 1-1/2" - 3" | 5/16" (0.3125") |
| 1/2" | 13 TPI (1/2"-13) | 4", 5", 6", 8" | 2" - 4" | 2" - 4" | 3/8" (0.375") |
| 5/8" | 11 TPI (5/8"-11) | 5", 6", 8" | 2-1/2" - 4" | 2-1/2" - 4" | 1/2" (0.500") |
Note: Thread lengths shown are approximate and may vary by manufacturer. Always verify actual dimensions before ordering for critical applications. Pilot hole sizes are for hardwoods; softwoods may use slightly smaller pilots.
Download Hanger Bolt Size Chart
Complete sizing reference with thread specifications and pilot hole sizes for all common hanger bolt diameters.
Download Size Chart (PDF)Size Selection Guidelines
How to Choose the Right Size
1. Calculate wood penetration needed: Generally 1.5 to 2 times the diameter for adequate holding power.
2. Determine required projection: Measure thickness of hardware plus nut height plus 2-3 threads extra.
3. Select total length: Wood penetration + hardware thickness + nut height + 1/4" clearance.
4. Consider load requirements: Heavier loads require larger diameters.
Example: To mount 1/4" thick bracket to 2x4 wood: 3/8" diameter x 3" length (1.5" into wood, 1.5" projection for bracket + nut).
Need Specific Sizes or Custom Lengths?
We stock a complete range of hanger bolt sizes with special order options for unusual specifications.
Shop All Sizes Request Custom QuoteInstallation Methods and Techniques
Proper installation of hanger bolts requires the right technique to avoid breaking the fastener or damaging the wood. The challenge is that there's no head to grip with conventional tools.
Method 1: Double-Nut Method (Most Common)
- Drill pilot hole: Use drill bit sized per chart (typically 75-80% of shank diameter for hardwood, 70% for softwood)
- Thread two nuts onto machine thread end: Run both nuts all the way up the threads
- Lock nuts together: Hold bottom nut with one wrench, tighten top nut against it to jam them together
- Drive wood threads: Use wrench on bottom (jammed) nut to turn hanger bolt clockwise into pilot hole
- Remove installation nuts: Once wood threads are fully seated, unlock and remove both nuts
Method 2: Hanger Bolt Installation Tool
Specialized tools are available that grip the center shank between threads, allowing you to drive the bolt without using nuts:
- Reduces installation time - no need to thread and remove nuts
- Better centering - grips closer to wood threads for straighter installation
- Less thread damage - machine threads remain pristine
- Available for common sizes - typically 1/4" through 5/8"
Method 3: Locking Pliers (Emergency Method)
Vise-grip or locking pliers can grip the smooth shank between threads in a pinch, but this method risks marring the threads and should be used only when other methods aren't available.
⚠️ Installation Best Practices
- Always drill pilot holes: Never try to drive hanger bolts without a pilot - this will split wood or break the bolt
- Use correct pilot size: Too large = weak hold, too small = split wood or broken bolt
- Keep it straight: Align carefully - angled installation weakens hold and may break the bolt
- Don't overtighten: Stop when wood threads are fully engaged; excessive force strips wood fibers
- Predrill in hardwoods: Dense woods like oak, maple, walnut require accurate pilot holes
- Check penetration: Ensure wood threads don't break through the back side
Download Pilot Hole Drilling Chart
Recommended pilot hole sizes by wood species and bolt diameter for optimal holding strength.
Download Pilot Hole Chart (PDF)Tools Required
- Drill and bits: Power drill with bits matching pilot hole sizes
- Wrenches: Two wrenches for double-nut method (one size for the nuts)
- Hanger bolt tool (optional): Specialized installation tool for easier driving
- Measuring tools: Ruler, depth gauge, or depth stop collar for consistent pilot depth
- Square or level: To ensure perpendicular installation
- Sockets and ratchet: For final assembly with nuts on machine thread end
Download Installation Guide
Step-by-step procedures for proper hanger bolt installation with illustrations and tips.
Download Installation Guide (PDF)Need Installation Tools or Hardware?
Shop drill bits, nuts, washers, and specialized hanger bolt installation tools.
Shop Nuts & WashersCommon Applications
Furniture Assembly
Attaching table legs, bed frames, and knockdown furniture where wood meets metal brackets or levelers.
- Table and desk leg mounting
- Bed frame assembly
- Furniture leveling feet
- Modular furniture connections
- Adjustable shelf brackets
Light Fixture Mounting
Installing pendant lights, chandeliers, and hanging fixtures to wood ceilings or beams.
- Ceiling light fixtures
- Chandelier hanging
- Pendant light installation
- Track lighting mounts
- Decorative hanging hardware
Shelving and Storage
Creating adjustable shelving systems and mounting storage brackets to wood structures.
- Adjustable shelf standards
- Garage storage systems
- Closet organization
- Wall-mounted brackets
- Heavy-duty shelving
Deck and Outdoor Construction
Attaching posts, railings, and hardware to deck and fence structures.
- Post cap installation
- Railing bracket mounting
- Deck board fastening
- Pergola hardware
- Outdoor furniture assembly
Equipment Mounting
Securing machinery, tools, and equipment to wood workbenches or platforms.
- Workbench vise mounting
- Tool installation
- Machinery leveling
- Equipment isolation mounts
- Shop fixture attachment
Cabinet Hardware
Installing handles, knobs, and adjustable feet on cabinetry and built-ins.
- Adjustable cabinet feet
- Leveling mechanisms
- Pull-out hardware
- Drawer slide mounting
- Door hardware installation
Download Application Guide
Common uses and project examples with recommended specifications for each application type.
Download Application Guide (PDF)Material and Finish Options
Carbon Steel (Zinc Plated)
Most common and economical option for indoor applications:
- Bright zinc: Thin zinc coating, basic corrosion protection, indoor use
- Yellow zinc: Slightly thicker coating, better protection, mild outdoor use
- Good strength: Adequate for most residential applications
- Widely available: Easy to find in common sizes
Hot-Dip Galvanized
Heavy zinc coating for outdoor and weather-exposed applications:
- Thick coating: Superior outdoor corrosion protection
- Deck and fence use: Ideal for treated lumber applications
- Long-term durability: Extended service life in weather
- Slightly higher cost: More expensive than zinc plated
Stainless Steel
Premium corrosion resistance for demanding environments:
- 304 grade: Excellent corrosion resistance, most applications
- 316 grade: Marine-grade, saltwater and chemical exposure
- No coating needed: Material itself resists corrosion
- Food-safe: Suitable for food service equipment
- Higher cost, lower availability: Premium option for critical applications
Finish Selection Guide
Indoor furniture/fixtures: Zinc plated sufficient
Outdoor decks/fences: Hot-dip galvanized recommended
Marine/coastal: 316 stainless steel required
Food service: 304 or 316 stainless steel
High-moisture areas: Galvanized or stainless
Load Capacity and Strength
Hanger bolt load capacity depends on multiple factors including diameter, wood species, installation depth, and load direction:
Factors Affecting Holding Strength
- Bolt diameter: Larger diameters provide greater shear and withdrawal strength
- Thread engagement depth: Deeper penetration into wood increases holding power
- Wood species and density: Hardwoods provide 2-3x holding power compared to softwoods
- Wood condition: Moisture content, age, and grain orientation affect strength
- Load direction: Withdrawal (pull-out) loads are weakest, shear loads are stronger
- Edge distance: Installation too close to wood edge reduces capacity significantly
Typical Withdrawal Values (Hardwood)
Approximate withdrawal loads for hanger bolts installed in oak with proper pilot holes and 1.5-2" penetration:
- 1/4" diameter: 200-300 lbs
- 5/16" diameter: 350-500 lbs
- 3/8" diameter: 500-700 lbs
- 1/2" diameter: 800-1200 lbs
- 5/8" diameter: 1200-1800 lbs
⚠️ Important Load Considerations
Use appropriate safety factors: For overhead or critical applications, apply minimum 4:1 safety factor.
Wood species matters: Values above are for hardwood. Softwoods (pine, fir) have 30-50% lower capacity.
Dynamic loads: Vibration, impact, and cyclic loading reduce long-term capacity - consult engineer for critical applications.
Multiple fasteners: Don't assume capacity multiplies linearly - adjacent fasteners interfere with each other's wood stress zones.
Ready to Order Hanger Bolts?
Browse our complete selection of hanger bolts in all sizes with same-day shipping on in-stock items.
Shop All Hanger Bolts Call for Bulk Pricing