What is tpi?

TPI: Threads Per Inch

TPI, or Threads Per Inch, is a measurement used to define the fineness or coarseness of a screw thread. It specifies the number of thread crests present within one inch of length along the screw.

  • Definition: TPI represents the quantity of threads counted per inch of a screw's length. A higher TPI value indicates a finer thread, meaning there are more threads packed into each inch. Conversely, a lower TPI signifies a coarser thread with fewer threads per inch.

  • Significance: Understanding TPI is crucial for selecting the correct fasteners for various applications. It affects the strength, holding power, and ease of assembly of threaded connections.

  • Application: TPI is commonly employed in industries such as machining, manufacturing, plumbing, and woodworking where precision and secure fastening are essential.

  • Measurement: Determining TPI involves counting the number of threads present within a one-inch segment of the screw. Specialized tools like thread gauges or pitch gauges can assist in this measurement.

  • Relationship to Pitch: TPI is inversely related to the pitch of a thread. Pitch refers to the distance between adjacent thread crests. The relationship is: Pitch = 1 / TPI. Understanding this relationship is key to correctly using and interpreting thread specifications.

  • Examples: Examples include 1/4-20 (coarse thread) and 1/4-28 (fine thread). The first number is the nominal diameter, and the second is the TPI.

Here are links to some important subjects that relate to TPI: