CFS CFS Fastener Head Styles & Drive Types 1 — Questions and Answers
Question 1: Which head style provides the largest bearing surface and is commonly used in wood and soft material applications?
- Flat head
- Pan head
- Truss head (Correct answer)
- Hex head
Correct 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.
Question 2: A Torx (star) drive fastener is designated by the letter 'T' followed by a number. What does the number represent?
- The number of points on the star
- A size code corresponding to the drive tool tip dimensions (Correct answer)
- The torque rating in inch-pounds
- The screw diameter in millimeters
Correct 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.
Question 3: Which drive type is specifically designed to provide a 'cam-out' effect to prevent overtightening on assembly lines?
- Hex socket (Allen)
- Torx Plus
- Phillips (Correct answer)
- Square (Robertson)
Correct 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.
Question 4: What distinguishes an oval (raised countersunk) head from a flat (countersunk) head?
- Oval heads require a larger countersink angle
- Oval heads have a slightly domed top surface above the countersink bearing surface (Correct answer)
- Oval heads use a different drive recess
- Oval heads have a larger bearing surface diameter
Correct 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.
Question 5: Which head style is most appropriate when a fastener must be flush with or below the work surface in a countersunk hole?
- Pan head
- Button head
- Flat (countersunk) head (Correct answer)
- Fillister head
Correct 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.
Question 6: A socket head cap screw uses which drive type and is typically tightened with what tool?
- Torx drive; T-handle
- Internal hex (Allen) drive; hex key or hex driver (Correct answer)
- Slotted drive; flathead screwdriver
- Phillips drive; #2 Phillips screwdriver
Correct 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.
CFS CFS Fastener Head Styles & Drive Types 1
Which head style provides the largest bearing surface and is commonly used in wood and soft material applications?