🔍 Key Concepts

• Properties of cast iron when being drilled or tapped • Purpose of cutting fluids and when they are or are not used • What chamfering the entrance of a threaded hole does for the tap and for the finished thread

💭 Think About

• Think about how brittle cast iron is: does it need lubrication to prevent galling, or does it naturally break into small chips? • Which option helps the tap start straight and protects the first few threads in the hole? • For an exam question, which choice reflects a standard best practice before you begin tapping any threaded hole?

✅ Before You Answer

• Verify which materials commonly are tapped dry because their chips break easily and contain graphite for lubrication • Consider whether mineral oil is the usual cutting fluid for cast iron, or if a different approach is recommended • Recall the normal sequence of taps: taper (starter) tap, plug tap, bottoming tap—which one is used first?