Understanding the pitch diameter

an important parameter in fasteners

The width of a cylinder (like a bolt) where the major and minor diameters cross at the middle is known as the pitch diameter. It is often referred to as the effective diameter or centerline. The ability of two threaded pieces to mesh firmly is directly impacted by this parameter. Pitch diameter is the distance between pitch circles in a gear set, while pitch circle is the trace left by the meshing contact points on each gear centerline. Surface flaws or wear cannot readily alter the pitch diameter, in contrast to the outside diameter (OD) or the interior diameter (ID).

The distance between the external thread's top and bottom crests is known as the major diameter.

The dimension that separates the top of the internal thread from the root of the external thread is known as the minor diameter.

Whether the thread is internal or external, the section that protrudes is called the crest.

Whether the thread is male or female, the root is the bottom of the groove that separates its two sides.

The angle between the tooth flanks as measured on the axial plane section is known as the thread angle.

The straight edge that joins the thread crest and thread root is known as the thread flank.

Pitch can be defined as the distance, measured in a direction parallel to the axis, between a point on one thread and the equivalent position on the next thread.