🔍 Key Concepts

• Pitch diameter is the diameter where the width of the thread and the width of the space between threads are equal • Difference between major diameter, minor (root) diameter, and pitch diameter on a screw thread • How the illustration marks diameters from crest-to-crest, root-to-root, and between the two

💭 Think About

• On the sketch, which lettered dimension is drawn at a diameter that lies between the outside (crest) of the thread and the very bottom (root) of the thread? • Which dimension appears to pass through the mid‑height of the thread flanks, rather than touching the very top or very bottom of the threads? • Looking at A, B, C, and H, which one best represents the imaginary cylinder where the thread thickness equals the groove width?

✅ Before You Answer

• Be sure you can point to the major diameter (outside/crest diameter) on the sketch before choosing • Identify the minor (root) diameter on the sketch and notice which letter is in between major and minor • Confirm that the dimension you choose looks like an imaginary diameter through the middle of the threads, not at their tops or bottoms