Red Seal Machinist Practice Exam

What does TPI stand for in machining?

1. Threads per inch

2. Threads per interval

3. Tool path index

4. Tool performance indicator

The correct answer is: Threads per inch

The term TPI stands for "Threads per inch," which is a crucial measurement in machining and manufacturing, particularly concerning threaded fasteners such as screws and bolts. Understanding TPI is essential because it specifies the density of threads along a given length of the fastener, providing critical information about its fit, strength, and application in various mechanical systems. In applications involving screw threads, a higher TPI indicates smaller, finer threads, which may provide better grip or be more suitable for precision applications, while a lower TPI yields larger threads that are typically stronger and may be used where greater load-bearing capacity is required. Recognizing TPI is important for machinists when selecting or designing threaded components to ensure compatibility and functionality in assembly, maintenance, or manufacturing processes.