The cross sectional shape of a thread is called its form or threadform. It can be square, triangular, trapezoidal or other. The term form refers to the shape, pitch and diameter of the thread. Most triangular threadforms are based on the isosceles triangle and are known as vee-threads because of the shape of the letter V. On 60 degree threads the isosceles triangle is more specifically, equilateral. For buttress threads the triangle is scalene. The theoretical triangle is normally truncated to varying degrees, meaning that the tip of the triangle is cut short. This truncation in manufacturing is deliberate for practical reasons such as the thread cutting tool cannot have a sharp point, it stops burring, the threads need clearance between mating parts, and it also creates stronger threads. The manufacture of a sharp thread would probably be impractical; the only application of such a thread would probably be used where a cutting action is required.
