CFS Fastener Head Styles & Drive Types Flashcards

Which head style provides the largest bearing surface and is commonly used in wood and soft material applications?

Answer: Truss head

Truss heads have an extra-wide, low-profile design that distributes load over a larger bearing area, making them ideal for soft or thin materials.

A Torx (star) drive fastener is designated by the letter 'T' followed by a number. What does the number represent?

Answer: A size code corresponding to the drive tool tip dimensions

The number following 'T' in a Torx designation (e.g., T25) is a size code that specifies the dimensional geometry of the drive tool tip, not a direct measurement.

Which drive type is specifically designed to provide a 'cam-out' effect to prevent overtightening on assembly lines?

Answer: Phillips

The Phillips drive was engineered with angled flanks that cause the driver to cam out when a set torque threshold is reached, limiting overtightening in production environments.

What distinguishes an oval (raised countersunk) head from a flat (countersunk) head?

Answer: Oval heads have a slightly domed top surface above the countersink bearing surface

An oval head has the same conical countersink bearing surface as a flat head but features a slightly rounded dome above the surface for a decorative or finished appearance.

Which head style is most appropriate when a fastener must be flush with or below the work surface in a countersunk hole?

Answer: Flat (countersunk) head

Flat (countersunk) heads are designed with a conical bearing surface that seats into a matching countersunk hole, allowing the fastener to sit flush or below the material surface.

A socket head cap screw uses which drive type and is typically tightened with what tool?

Answer: Internal hex (Allen) drive; hex key or hex driver

Socket head cap screws feature an internal hexagonal (Allen) recess and are tightened with a hex key (Allen wrench) or power hex driver.