Sex Bolts & Barrel Nuts: Complete Guide
Chicago Screws, Binding Posts & Screw Posts for Professional Through-Bolting
Types & Styles
Standard, low-profile, and specialty configurations
Size Charts
Complete sizing for barrel and screw lengths
Applications
Furniture, albums, leather goods, and more
Installation
Proper assembly techniques and tips
Downloadable Reference Guides
Quick access to all sex bolt specification charts and guides
What Are Sex Bolts and Barrel Nuts?
Sex bolts (also called barrel nuts, Chicago screws, binding posts, or screw posts) are two-piece fasteners designed for through-bolting applications where a clean, finished appearance is needed on both sides of the assembly. Unlike traditional nuts and bolts, sex bolts feature a female-threaded barrel that receives a male machine screw, creating a low-profile, symmetrical connection.
The name "sex bolt" comes from the mating of male (screw) and female (barrel) components. These fasteners are particularly popular in furniture, leatherwork, bookbinding, and any application requiring a removable, attractive fastener that looks good from both sides.
Key Advantages of Sex Bolts
Dual finished appearance: Clean, professional look on both sides of the assembly without exposed threads.
Low profile: Minimal protrusion on both sides compared to traditional nut and bolt assemblies.
Easy disassembly: Can be removed and reinstalled multiple times without damage.
Versatile sizing: Available in many lengths to accommodate different material thicknesses.
No threading damage: Barrel protects internal threads from damage during handling.
Sex Bolt Types and Configurations
Standard Sex Bolts
Classic two-piece design with flat-head barrel and mating machine screw for general-purpose through-bolting.
- Flat barrel head (both sides)
- Female-threaded barrel
- Mating male machine screw
- Most common configuration
- Brass, aluminum, or steel
Chicago Screws
Specific style of sex bolt with slotted heads on both pieces, commonly used in leather goods and bookbinding.
- Slotted heads (both barrel and screw)
- Nickel or brass finish typical
- Leather and book binding standard
- Multiple finish options
- Various post lengths available
Binding Posts
Extended-barrel style designed specifically for binding documents, albums, and multi-page assemblies.
- Longer barrels for thick stacks
- Often have decorative heads
- Available in 1/4" to 3" lengths
- Album and portfolio standard
- Nickel, brass, or black finish
Low-Profile Sex Bolts
Reduced head height on barrel for applications with clearance restrictions or flush-mounting requirements.
- Ultra-thin barrel head
- Countersunk screw option
- Electronics and panels
- Tight clearance applications
- Aluminum or steel
Decorative Sex Bolts
Fashion-forward designs with decorative heads for visible installations in furniture, bags, and accessories.
- Ornamental head designs
- Antique or polished finishes
- Leather goods and fashion
- Custom engraving available
- Multiple colors and styles
Shoulder Screw Sex Bolts
Hybrid design combining shoulder screw precision with barrel nut convenience for pivot applications.
- Precision shoulder on screw
- Bearing surface for rotation
- Threaded portion for barrel
- Pivot and hinge applications
- Limited availability
Need Help Selecting Sex Bolts?
Our fastener experts can help you choose the right barrel length, thread size, and finish for your application.
Call (866) 573-0445Sex Bolt Sizing and Specifications
Sex bolts are specified by thread size, barrel length (or "post length"), and head diameter. Understanding these dimensions is critical for proper fit:
Key Dimensions
- Thread Size: The diameter and pitch of both the male screw and female barrel threads (must match)
- Barrel Length (Post Length): The overall length of the female barrel, which determines maximum material thickness
- Barrel Head Diameter: The outer diameter of the barrel's head (varies by style)
- Screw Length: Total length of the male screw portion (typically slightly shorter than barrel for clearance)
- Head Diameter: The outer diameter of the screw's head (usually matches barrel head)
Sizing Formula
Required Barrel Length = Material Thickness + 1/16" to 1/8" clearance
Example: For 1/2" thick material, use 9/16" to 5/8" barrel length to ensure proper clamping without bottoming out.
Always select the next standard size up if exact match is not available - slightly longer is better than too short.
Standard Thread Sizes
| Thread Size | Typical Head Diameter | Common Barrel Lengths | Max Material Thickness | Typical Uses |
|---|---|---|---|---|
| M3 (3mm) | 6-8mm | 4-15mm | 3-14mm | Electronics, small leather goods |
| M4 (4mm) | 8-10mm | 6-20mm | 5-18mm | Light assemblies, thin panels |
| M5 (5mm) | 10-12mm | 8-25mm | 7-23mm | General purpose, leather goods |
| 6-32 | 5/16"-3/8" | 3/16"-1" | 1/8"-15/16" | Common American size, albums |
| 8-32 | 3/8"-1/2" | 1/4"-1-1/4" | 3/16"-1-1/8" | Furniture, heavy leather goods |
| 10-24 | 1/2"-5/8" | 1/4"-1-1/2" | 3/16"-1-3/8" | Heavy furniture, structural |
| 1/4"-20 | 1/2"-3/4" | 3/8"-2" | 1/4"-1-7/8" | Large furniture, industrial |
Download Sex Bolt Size Chart
Complete sizing reference for thread sizes, barrel lengths, and head dimensions.
Download Size Chart (PDF)Material and Finish Options
| Material | Finish Options | Corrosion Resistance | Best For |
|---|---|---|---|
| Brass | Polished, antique, lacquered | Excellent (natural patina) | Decorative, leather goods, marine |
| Stainless Steel | Polished, brushed, black oxide | Excellent (all conditions) | Outdoor, marine, food service |
| Aluminum | Anodized (various colors), natural | Good (anodized) | Lightweight applications, colored |
| Steel | Zinc, nickel, black oxide, chrome | Moderate (with finish) | Indoor, general purpose, economical |
| Nylon | Natural (white), black | Excellent (non-metallic) | Electrical insulation, light duty |
Download Material Selection Guide
Detailed material properties, finishes, and application recommendations for choosing the right sex bolt.
Download Material Guide (PDF)Need Custom Lengths or Finishes?
We can source specialty sizes and custom finishes for unique applications and large orders.
Request Custom QuoteCommon Applications
Furniture Assembly
Clean through-bolting for modern furniture with visible hardware as a design element.
- Table and desk legs
- Chair and bench connections
- Shelf brackets and supports
- Bed frame assemblies
- Modular furniture systems
Leather Goods & Fashion
Essential fastener for bag straps, belts, and leather accessories requiring clean, removable connections.
- Bag and purse handles
- Adjustable belt buckles
- Wallet closures
- Jacket and vest hardware
- Decorative leather accents
Albums & Portfolios
Binding posts allow page addition/removal while maintaining professional appearance and structural integrity.
- Photo albums and scrapbooks
- Portfolio presentations
- Swatch books and samples
- Menu covers
- Document binders
Signage & Displays
Stand-off mounting creates floating effect while providing strong, removable attachment for graphics.
- Acrylic sign mounting
- Wall-mounted displays
- Retail fixtures
- Menu boards
- Information panels
Electronics Enclosures
Low-profile sex bolts provide secure panel attachment with easy disassembly for service access.
- Equipment rack panels
- Computer case assemblies
- Control panel covers
- Instrument housings
- Junction boxes
Art & Craft Projects
Versatile fastening solution for creative applications where aesthetics and adjustability are important.
- Mixed media artwork
- Handmade journals
- Wooden toy assemblies
- Custom lamp construction
- DIY furniture projects
Download Application Guide
Comprehensive guide to sex bolt applications by industry, material selection, and sizing recommendations.
Download Application Guide (PDF)Installation and Assembly Guidelines
Proper Installation Procedure
- Measure material thickness: Use calipers or ruler to measure exact thickness of all materials being joined
- Select barrel length: Choose barrel length 1/16"-1/8" longer than total material thickness
- Mark hole locations: Use template or careful measurement to ensure aligned holes
- Drill pilot holes: Drill clearance holes sized for free passage of barrel body (not head)
- Deburr holes: Remove sharp edges that could prevent proper seating
- Insert barrel: Place female barrel through holes from one side
- Thread screw: Start male screw by hand, turning slowly to avoid cross-threading
- Tighten gradually: Use appropriate driver to tighten until components are firmly clamped
- Check alignment: Verify parts are properly aligned and not distorted by overtightening
Hole Sizing Guide
| Thread Size | Barrel Body Diameter | Recommended Clearance Hole | Tight Fit Hole |
|---|---|---|---|
| M3 | ~4.5mm | 4.8mm (3/16") | 4.6mm |
| M4 | ~6mm | 6.5mm (1/4") | 6.2mm |
| M5 | ~7.5mm | 8mm (5/16") | 7.7mm |
| 6-32 | ~0.180" | 13/64" (0.203") | #11 (0.191") |
| 8-32 | ~0.230" | 1/4" (0.250") | #3 (0.237") |
| 10-24 | ~0.290" | 5/16" (0.3125") | #2 (0.302") |
| 1/4"-20 | ~0.350" | 3/8" (0.375") | U (0.368") |
⚠️ Installation Best Practices
Don't overtighten: Excessive force can strip threads, especially in soft materials like brass. Hand-tight plus 1/4 turn is usually sufficient.
Align holes carefully: Misaligned holes cause binding and thread damage. Use templates or careful marking.
Check barrel length: If barrel is too long, components won't clamp. If too short, threads won't engage fully.
Support thin materials: Use backup washers on soft or thin materials to prevent pull-through.
Use thread locker sparingly: Only on permanent installations - makes future disassembly difficult.
Assembly Tips for Specific Materials
- Leather: Use leather punches instead of drilling for cleaner holes. Slightly undersized holes provide better grip
- Wood: Pre-drill to prevent splitting. Use finish washers for polished appearance
- Acrylic/Plastic: Drill slowly to prevent cracking. Deburr carefully to avoid stress concentrations
- Fabric/Canvas: Use grommets or reinforcement rings around holes for increased strength
- Metal: Deburr thoroughly. Consider anti-seize compound for dissimilar metals to prevent galvanic corrosion
Download Installation Guide
Step-by-step installation instructions with hole sizing charts and assembly tips.
Download Installation Guide (PDF)