Definition

Noun: 1. A type of fastener: A cap screw is a threaded fastener, similar to a bolt, designed to be screwed into a pre-tapped (internally threaded) hole in a machine part or assembly. It is typically characterized by a cylindrical head with a hexagonal socket (Allen key) or a similar drive feature.

Usage and Examples

• General Use: Cap screws are used to securely join machine components where a bolt and nut would be impractical.
  • The engineer selected a high-strength cap screw to attach the gearbox housing.
  • Ensure the cap screw is tightened to the specified torque.
• In Manufacturing/Assembly: They are common in precision equipment, engines, and machinery.
  • The assembly manual lists the required cap screw size for this joint.
  • Remove the four cap screws to access the internal mechanism.

Advanced Usage and Technical Context

• Distinction from Bolt: In technical contexts, a "cap screw" is often distinguished from a "bolt." A cap screw is designed to be used with a tapped hole, while a bolt is designed to be used with a nut. However, in common usage, the terms are sometimes used interchangeably.
• Head Types: While often associated with socket heads, cap screws can also have other head styles (e.g., button head, flat head) that sit flush with or within the material surface.

Variants and Related Words

• Socket Head Cap Screw (SHCS): The most common type, featuring a cylindrical head with a hexagonal socket.
• Hex Cap Screw: A heavy-duty fastener with a hexagonal head, designed to be used with a wrench. It is often used similarly to a bolt but is engineered to mate with a tapped hole.
• Machine Screw: A smaller, finely threaded screw, typically used with a nut or tapped hole. Cap screws are generally larger and stronger than standard machine screws.

Synonyms

• Fastener
• Machine screw (in some contexts)
• Socket screw (when referring to socket head types)

Notes on Meaning

The core meaning of "cap screw" is a threaded fastener for machine parts that screws into a tapped hole. Its defining characteristic in engineering is its intended use with a pre-threaded hole rather than a nut. The specific design (head style, drive type, material) can vary based on application requirements.

Noun

1. a threaded screw for machine parts; screws into a tapped hole