🔍 Key Concepts

• Twist drill geometry: included point angle vs. lip clearance • Effect of workpiece hardness on drilling parameters • Difference between cutting speed and drill size (diameter)

💭 Think About

• How does increasing the hardness of the metal change the shape or setup of the drill rather than just how fast you spin it? • Which part of a twist drill controls how strong the cutting edge is and how likely it is to chip or wear in hard material? • Think about drilling soft aluminum vs. hardened steel: which feature of the drill must change to support a stronger, blunter cutting edge?

✅ Before You Answer

• Be clear on what included point angle means (the angle at the very tip formed by the two cutting edges). • Know that cutting speed is usually reduced, not increased, for harder metals. • Remember that diameter is usually chosen by the required hole size, not by hardness of the metal.