What is plunge drilling?
Plunge drilling is an effective method for roughing out cavities. It makes a deeper hole or cavity through repeated axial cuts using a drill or milling cutter and is especially suitable for rough machining. It is power-efficient, productive and reduces demands on the machine tool spindle as the main cutting forces are directed axially along the spindle. Internal plunge milling is started by drilling a hole for the plunging tool.
Choice of tools
Indexable drills are used for centre cutting with two inserts and are very productive. Seventy percent of the drill diameter can be applied to the next overlapping cut if you use the plunge drill at full indexable insert drill cutting data. Metal removal rate is high.
Plunge milling is similar to plunge drilling using an indexable insert cutter, a round insert cutter or a solid carbide drill. However, a milling cutter has limited step-over – only half of the axial insert cutting edge length. It can be an interesting alternative when diameters are large enough to have a number of teeth engaged to provide high feeds.
- For best stability, always use the shortest possible drill
- Always use internal coolant to ensure sufficient chip evacuation
- Maximum step-over rate is 70% of the drill diameter. This provides an efficient cavity-creation rate while ensuring no material-cores are left in the cavity
- Before plunging, a hole must be drilled conventionally to start the creation of the cavity
- It is beneficial to drill two holes and plunge between them. This leaves plenty of space for chip evacuation