What determines the thread percentage in machining?

The thread percentage in machining is primarily determined by the tap hole diameter. The tap hole diameter is critical because it establishes the minor and major diameters of the screw thread, impacting how full the threads are when the tap is inserted. A properly sized hole for the tap ensures that the threads are cut to the correct depth and profile, which directly relates to how much of the thread is engaged in the material being machined.

The machined threads' profile can affect their strength and functionality, especially when screws are being torqued or subjected to tensile forces. If the tap hole diameter is not appropriate for the specified thread size, it could lead to insufficient thread depth or an improper fit, thus altering the effective percentage of the thread engagement, which is essential for ensuring secure assembly in mechanical applications.

While factors like tool material, type of cutting fluid, and feed rate can influence the machining process, they do not specify the geometry and engagement of the threads to the same extent as the tap hole diameter. These elements can affect the cutting efficiency, surface finish, and tool wear but don't directly dictate how the threading is engaged with the material.