2BA Screw

2BA Screw: Precision British Standard Fastener

A 2BA screw is a type of machine screw that adheres to the British Association (BA) thread system, a set of screw threads historically used in precision engineering and electrical applications throughout the United Kingdom and Commonwealth countries . The “2BA” designation indicates a specific thread size within this imperial-based system.

These screws are fully threaded and designed to be used in pre-tapped holes or with conforming nuts and washers in through-hole applications . As machine screws, they function similarly to bolts but feature a socket or drive in the head that allows them to be turned with a screwdriver or hex key .

2BA screws remain popular today for maintenance of vintage equipment, specialist engineering projects, and applications where a fine, precise thread is required in confined spaces.

2BA Screw: Key Specifications

2BA Screw: Understanding BA Threads

The British Association (BA) thread system was developed in the 19th century to provide a range of small, fine-pitch threads for precision instrumentation and electrical work. Unlike metric or unified threads, BA threads are defined by a thread angle of 47.5 degrees, which differs from the more common 60-degree angle found in metric and UNC threads.

The 2BA thread size sits in the middle of the BA range. It has a nominal diameter of approximately 4.7mm and a fine pitch of 31.35 threads per inch . This fine pitch allows for precise adjustment and strong holding power in thin materials, making it ideal for electrical terminals, instrument mounting, and electronic assemblies.

All BA threads are governed by rigorous standards, with slotted head screws typically manufactured to BS 57:1951  and socket head screws to BS 2470 .

2BA Screw: Head Styles and Drive Types

2BA screws are available in numerous head configurations to suit different applications:

Round Head (Slotted): Features a domed head that sits above the surface, providing a neat, decorative appearance. Commonly used in electrical equipment and decorative applications where the head is visible .

Countersunk Head: Designed to sit flush with the surface when installed, providing a smooth, snag-free finish. Available in 90-degree countersunk angle . Ideal for applications requiring a flush surface .

Raised Countersunk Head: Combines a countersunk profile with a slightly domed top, offering both flush fit and decorative appeal .

Cheese Head: Features a broad, flat head with vertical sides, providing excellent clamping force and a wide bearing surface .

Button Head (Socket): Low-profile domed head with internal hex drive, suitable for applications requiring a smooth appearance with secure fastening .

Socket Head Cap: Cylindrical head with internal hex drive, offering high tightening torque capability for demanding applications .

Drive types include traditional slotted (flat-blade screwdriver) , hexagon socket (Allen key) , and Phillips drive options.

2BA Screw: Material Options

The choice of material determines the screw’s strength, corrosion resistance, and suitability for specific environments:

Brass: Offers excellent corrosion resistance and an attractive appearance, often with nickel-plated finish to resist tarnishing . Commonly used in electrical applications, decorative fittings, and environments where non-magnetic properties are required .

Stainless Steel (A2): Provides superior corrosion resistance and durability, ideal for outdoor use, marine environments, and applications requiring long-term reliability . A2 stainless steel (also known as 18/8 or type 304) offers excellent strength-to-weight ratio .

High-Grade Alloy Steel: Available in grades 8.8, 10.9, and 12.9 for high-tensile applications requiring maximum strength . Suitable for automotive, aerospace, and heavy engineering where load-bearing capacity is critical. Maximum operating temperature up to 300°C .

2BA Screw: Applications

2BA screws find use across numerous industries and applications:

Electrical Equipment: Terminal connections, switchgear assembly, control panel mounting, and component fixing .

Precision Instruments: Mounting of delicate components, adjustment mechanisms, and calibration equipment.

Vintage and Classic Restoration: Maintenance and restoration of vintage radios, test equipment, motorcycles, cars, and machinery originally manufactured with BA threads.

Automotive and Aerospace: Where high-tensile strength and precise thread forms are required .

General Engineering: Machine parts, jigs and fixtures, prototype assembly, and production manufacturing .

Decorative Applications: Due to the high-quality finish available in brass and plated options, 2BA screws are often used for visible decorative fittings .

2BA Screw: Installation and Use

Proper installation ensures optimal performance and joint integrity:

1. Select the Correct Drive: Ensure your screwdriver or hex key matches the drive type and size for optimal torque application without damaging the head .

2. Prepare the Hole: For tapping, use the correct size tap drill for 2BA threads. For through-hole applications, select a clearance drill slightly larger than the thread diameter.

3. Use Compatible Nuts and Washers: 2BA nuts and washers are available to complement the screws, ensuring proper thread engagement and load distribution .

4. Apply Appropriate Torque: Avoid over-tightening, which can strip threads or damage materials. For high-strength steel screws, refer to recommended torque specifications.

5. Consider Thread Locking: For high-vibration environments, thread-locking patches or nylon insert nuts can prevent loosening .

2BA Screw: Quality and Compliance

Quality 2BA screws are manufactured to rigorous British Standards:

• BS 57 : 1951: Specification for slotted head screws, including raised countersunk and round head types .

• BS 2470 : 1936 Series: Specification for socket head screws .

• BS EN ISO 898/1: Mechanical properties of fasteners – carbon steel and alloy steel .

• RoHS and REACH Certified: Ensuring materials are free from hazardous substances .

• ISO 9001: Quality management systems ensure consistent manufacturing standards .

2BA Screw: Availability and Packaging

2BA screws are available in various packaging options to suit different requirements:

• Individual Pieces: For small projects, repairs, and prototype work .

• Packs of 50, 100, or 200: For production runs and regular maintenance .

• Bulk Quantities: For large-scale manufacturing and industrial applications.

When installed correctly with compatible nuts and washers, 2BA screws provide reliable, long-lasting fastening solutions for a wide range of precision engineering, electrical, and general applications.