🔍 Key Concepts

• How a micrometer actually grips and measures round objects • Which part of a twist drill determines the size of the hole it will cut • The difference between supporting sections of the tool vs. cutting or guiding surfaces

💭 Think About

• Ask yourself: which part of the drill does the work of cutting the hole to a particular diameter? • Consider: if you measured this other part instead, would you get the same value as the hole diameter? • Think about how a micrometer’s anvils contact a cylindrical surface—where should they touch to read the true cutting size?

✅ Before You Answer

• Make sure you’re focusing on the cutting diameter, not the strength or support section of the drill • Eliminate any surfaces that are recessed or relieved, since they won’t represent the full cutting diameter • Check which feature actually defines the nominal drill size stamped on the tool