A pitch tap, often also referred to as the root diameter, relates to screw threads and represents the distance between corresponding points on adjacent threads. In simpler terms, it describes how tightly packed the threads of a screw are. The pitch is numerically equivalent to one divided by the number of threads per inch (TPI).
Essentially, understanding pitch is crucial when working with screws and fasteners because it dictates compatibility and the force required for tightening.
Understanding Screw Thread Pitch
- Definition: The distance measured from a point on one screw thread to the corresponding point on the next adjacent thread.
- Measurement: Pitch is typically measured in millimeters (mm) for metric threads and as threads per inch (TPI) for imperial threads.
- Calculation: Pitch = 1 / TPI
Importance of Pitch
- Compatibility: Using screws and nuts with mismatched pitches will prevent proper fastening.
- Force Application: Finer pitches (more threads per inch) generally provide greater clamping force but require more turns. Coarser pitches allow for faster assembly but may offer less holding power.
- Stripping Risk: Incorrectly mating screws can easily lead to stripping of the threads.
Example
If a screw has 20 threads per inch (TPI), its pitch is 1/20 inch.
Summary
"Pitch tap" essentially refers to the thread pitch on a screw, a critical specification for ensuring proper mating and functionality.
