🔍 Key Concepts

• Meaning of standard US screw thread notation such as 1/4-20 • Difference between diameter and threads per inch (TPI) • How taps are labeled in machine shop and marine maintenance contexts

💭 Think About

• What does the first number in a designation like 1/4-20 usually describe about the screw or tap? • What does the second number typically refer to when we talk about screw threads in inches? • Look at which choices confuse total number of threads with threads per inch or with length.

✅ Before You Answer

• Identify which answer correctly treats 1/4 as a measurement of diameter, not length. • Check which option correctly interprets 20 as a rate (threads per inch), not a total count of threads. • Eliminate any choice that mixes up pitch (distance between threads) with total number of threads.