What is the term for a ridge of uniform section in the form of a helix cut around the circumference of a cylinder?

The term for a ridge of uniform section in the form of a helix cut around the circumference of a cylinder is "screw threads." Screw threads are essential features in mechanical design, used for fastening, adjusting, and converting rotational motion into linear motion.

Screw threads can be found in various applications, from bolts and screws to nuts and gear systems. The helical shape allows for a large surface area for contact, which increases the strength and grip when two threaded components are interlocked. This design allows for precise control of movement and load distribution in mechanical assemblies.

The other options refer to different concepts in machine design. For instance, thread roots pertain to the bottom part of the threads where they meet, not the helical feature itself. A helix thread is less commonly used as a term but could be confused with the general concept of a screw thread without specifically denoting the function. Chamfers refer to beveled edges and do not describe any helical feature. Therefore, the definition and applications of screw threads align perfectly with the description given in the question.