🔍 Key Concepts

• Micrometer parts: distinguish the sleeve (barrel) scale, thimble scale, and the small vernier scale on the sleeve used for ten‑thousandths of an inch. • Basic reading rule: total reading = sleeve whole/half turns (0.100, 0.025 in) + thimble reading (each division usually 0.001 in) + vernier reading (each division usually 0.0001 in). • On figure C, pay close attention to which sleeve line is just fully visible to the left of the thimble edge, and which vernier line lines up exactly with a thimble graduation.

💭 Think About

• First, decide what the sleeve reading is: how many 0.100" and 0.025" marks have passed the edge of the thimble on figure C? Which tenth and hundredth of an inch does that place you in? • Next, find which thimble line lies exactly on the sleeve reference line. How many thousandths does that add, and does it put you closer to .47 or .48 in? • Finally, look at the vernier scale: which vernier division lines up perfectly with a thimble mark? How many ten‑thousandths does that add, and how does that help you distinguish between the four choices?

✅ Before You Answer

• Be sure you are not counting any sleeve graduation that is partly covered by the thimble; only fully exposed marks to the left of the thimble edge are included. • Confirm the thimble scale value per division (usually 0.001 inch per line) before multiplying by the number of lines past zero. • When using the vernier, verify exactly one vernier line coincides with a thimble line; multiply its number by the vernier value (commonly 0.0001 inch) and add it last.