Threads, Fasteners & Springs — A screw thread is a ridge of uniform section, formed as a helix on the external or internal surface of a cylinder, used to convert rotary motion to linear motion and to create clamping force in fasteners.

Introduction / Context:
Screw threads are foundational to mechanical design and manufacturing. They appear on bolts, screws, studs, and inside nuts or tapped holes, enabling power transmission and reliable clamping. The definition hinges on two key ideas: a uniform-profile ridge and a helical path on a cylindrical (or sometimes conical) surface.

Given Data / Assumptions:

• The thread has a uniform cross-sectional profile (form) along its length.
• The ridge follows a helical path around a cylindrical surface (external or internal).
• Use is general-purpose fastening or motion conversion.

Concept / Approach:
A thread’s geometry is described by its form (profile), pitch, lead, major/minor/ pitch diameters, and helix angle. Uniformity of the section ensures consistent engagement and predictable load distribution between mating parts.

Step-by-Step Solution:
1) Identify the ridge profile (e.g., V-form, square, trapezoidal).2) Confirm the path is helical around a cylinder or inside a hole.3) Check uniformity: the same profile repeats at each pitch interval.4) Conclude the statement matches standard thread definitions.

Verification / Alternative check:
Inspect a bolt and a matching nut: the external and internal ridges share a uniform form and engage via a helical path, validating the definition.

Why Other Options Are Wrong:
Limiting threads to external surfaces or claiming non-uniform sections contradicts standard practice. Conical threads exist (e.g., pipe threads), but the statement correctly centers on cylindrical surfaces, which are most common.

Common Pitfalls:
Confusing thread form (profile) with path; assuming only external threading qualifies; ignoring that uniformity is crucial for fit and load sharing.

Final Answer:
Correct