🔍 Key Concepts

• How bolt sizes and threads per inch (TPI) are labeled • Difference between pipe thread designations (like NPT) and machine screw/bolt designations • What the two numbers in a designation like 1/4-20 usually represent in mechanical/fastener context

💭 Think About

• Ask yourself: does 1/4-20 look more like a description of diameter and number of threads per inch, or something else like thickness or tip size? • Which of the choices commonly uses a format of fraction – whole number to describe diameter and thread count? • Think about where you’ve seen markings like 10-24, 1/4-20, 5/16-18 in shop or maintenance work—what were those items?

✅ Before You Answer

• Verify which item among the choices is normally described by diameter × threads per inch (TPI). • Check whether pipe threads are usually labeled only with two numbers like 1/4-20, or if they typically include a type designation (e.g., NPT). • Confirm that plate thickness and torch tip sizes are not normally specified in a “diameter–threads per inch” format.