Chicago screws, also known as binding posts, sex bolts, or barrel nuts and screws, are two-piece fasteners used in furniture, signage, architectural hardware, displays, bookbinding, leather goods, and OEM assemblies.
A typical Chicago screw consists of a female threaded post and a matching male screw. The two pieces fasten together to create a clean finished appearance on both sides of the assembly.
Chicago screws are available in different thread sizes, post lengths, body diameters, materials, head styles, and drive options, including standard and tamper-resistant designs.
This guide explains the most important differences and how to choose the right size and style for your application.
What Is a Chicago Screw?
A Chicago screw consists of:
- a female internally threaded post
- a matching male screw
The male screw threads into the female post and clamps the material between the two heads.
The same general fastener may be described by several names depending on the industry.
| Term | Common Meaning |
|---|---|
| Chicago Screw | Complete male and female fastener assembly |
| Binding Post | Usually the female threaded post |
| Sex Bolt | Industrial term for a male and female fastener assembly |
| Barrel Nut & Screw | Common in furniture, architectural and security applications |
For most purchasing applications, the exact dimensions, thread size, material, and drive style are more important than the name used.
Internal link: [Binding Posts & Screws]
Common Chicago Screw Sizes
Chicago screws and binding posts are available in many thread sizes.
Common inch sizes include:
- #8-32
- 10-24
- 10-32
- 1/4-20
- 5/16-18
The correct thread size depends on the application, hole size, required strength, and mating screw.
For example, a 10-24 Chicago screw and a 1/4-20 Chicago screw use different thread diameters and pitches and are not interchangeable.
When selecting a Chicago screw, also check these dimensions:
Post Length
The post length should match the thickness of the materials being fastened.
Body Diameter
The body or barrel diameter determines the required hole size.
This is especially important when replacing an existing binding post.
Head Diameter
Head diameter affects the bearing surface and finished appearance.
Head Height
Head height determines how far the fastener projects above the surface.
For replacement parts, it is best to check all major dimensions rather than ordering by thread size alone.
Open-End vs. Closed-End Binding Posts
Chicago screws are commonly available with either an open-end or closed-end binding post.
Closed-End Binding Posts
A closed-end binding post has a sealed bottom that limits how far the mating screw can enter.
Closed-end designs are useful when you need:
- controlled screw depth
- a clean finished appearance
- protection from screw protrusion
Internal link: [Closed-End Binding Posts & Screws]
Open-End Binding Posts
An open-end binding post allows greater screw engagement and can provide more flexibility when material thickness varies.
They are commonly used for:
- thicker assemblies
- multiple material layers
- different screw lengths
- applications requiring additional thread engagement
Internal link: [Open-End Binding Posts & Screws]
Chicago Screw Drive Styles
The drive style affects both installation and removal.
Slotted, Phillips and Combination Drives
Standard slotted, Phillips, and Phillips/slotted combination drives are practical for general-purpose applications and can be installed using common tools.
Six-Lobe / Torx Drive
Six-lobe, commonly called Torx-style, drives provide positive tool engagement and are widely used in:
- furniture
- architectural hardware
- commercial fixtures
- equipment
- OEM assemblies
Internal link: [Six-Lobe / Torx Barrel Nuts & Screws]
Security Pin Torx
A six-lobe security drive includes a center pin and requires a matching security bit.
This helps reduce unauthorized removal in applications such as:
- public facilities
- restroom partitions
- commercial furniture
- signage
- architectural hardware
Internal link: [Security Torx Barrel Nuts & Screws]
One-Way Security Drive
One-way Chicago screws are designed for easy installation while making removal with a standard screwdriver more difficult.
They are commonly used where tamper resistance is important.
Internal link: [One-Way Security Barrel Nuts & Screws]
Chicago Screw Materials
The right material depends on strength, corrosion resistance, appearance, weight, and cost.
Steel
Steel Chicago screws are strong and economical for many industrial and commercial applications.
Zinc plating and other finishes can provide additional corrosion protection.
Stainless Steel
Stainless steel binding posts are commonly used when corrosion resistance and appearance are important.
Typical applications include architectural hardware, commercial fixtures, outdoor equipment, and high-moisture environments.
Aluminum
Aluminum Chicago screws are lightweight and naturally corrosion resistant.
They are often used for displays, binding, leather goods, and other applications where lower weight is preferred.
Brass
Brass binding posts provide a decorative appearance and are often selected for furniture, architectural hardware, leather goods, and specialty applications.
How to Choose the Right Chicago Screw
When selecting or requesting a quote for a Chicago screw, provide as much of the following information as possible:
- Thread size
- Post length
- Body diameter
- Head diameter
- Head style
- Drive style
- Material
- Finish
- Required quantity
If you do not know the specifications, a drawing or physical sample can also be used to identify the correct dimensions.
Important: Do Not Measure Length Only
Two binding posts may have similar overall lengths but different:
- thread sizes
- body diameters
- head diameters
- screw engagement
- materials
- drive styles
For OEM and replacement applications, dimensional confirmation is always recommended.
Binding Post Extensions
If an existing binding post is too short, a binding post extension may be used in some applications to increase the usable length.
Extensions are useful when:
- material thickness increases
- another layer is added
- an existing assembly needs additional length
The extension thread must match the existing binding post.
Internal link: [Binding Post Extensions / Extension Screws]
Common Chicago Screw Applications
Chicago screws are used across many industries.
Furniture
Used for panels, cabinets, frames, seating, and other assemblies where a clean finish is desired.
Architectural Hardware
Common in partitions, panels, fixtures, and other commercial installations.
Signage and Displays
Useful for mounting removable signs, panels, displays, and presentation systems.
Leather Goods
Smaller Chicago screws are commonly used in belts, bags, straps, cases, and accessories.
Bookbinding and Sample Books
Binding posts are widely used for menus, catalogs, swatch books, portfolios, and sample kits.
Industrial and OEM Equipment
Custom and standard barrel nuts and screws can be used in equipment, enclosures, panels, covers, and manufactured assemblies.
Public and Commercial Facilities
Security Chicago screws are useful where tamper resistance is required.
Standard and Custom Chicago Screws
Standard Chicago screw sizes are often the fastest and most economical solution.
However, OEM applications may require custom specifications such as:
- custom thread size
- custom post length
- custom body diameter
- special head diameter
- special head style
- security drive
- custom material
- plating or finish
Imperial Rivets & Fasteners supplies standard and custom Chicago screws, binding posts, barrel nuts, and screws for industrial and OEM applications.
We support common sizes as well as custom fastening requirements for applications where standard products do not fit.
Frequently Asked Questions About Chicago Screws
Are Chicago screws and binding posts the same?
The terms are often used interchangeably. A binding post usually refers to the female threaded post, while Chicago screw often refers to the complete male and female assembly.
What are common Chicago screw sizes?
Common inch thread sizes include #8-32, 10-24, 10-32, 1/4-20, and 5/16-18. Available sizes vary by product style.
What is the difference between 10-24 and 1/4-20 Chicago screws?
They have different thread diameters and thread pitches and cannot be used interchangeably.
What is the difference between open-end and closed-end binding posts?
A closed-end post limits screw depth. An open-end post allows greater screw engagement and can accommodate more variation in assembly thickness.
Are security Chicago screws available?
Yes. Security options include six-lobe/Torx with center pin, one-way drives, and other tamper-resistant configurations.
Can Chicago screws be custom made?
Yes. Custom Chicago screws can be manufactured with different thread sizes, lengths, diameters, heads, drives, materials, and finishes.
Need Chicago Screws or Binding Posts?
Need help finding the correct Chicago screw size, binding post, barrel nut, or security fastener?
Send us your:
- drawing or sample
- thread size
- dimensions
- material and finish
- application
- required quantity
Imperial Rivets & Fasteners supplies stock and custom Chicago screws and binding posts for OEM and industrial applications.
Need a size you don’t see? Contact us for availability, samples, or a custom quote.
