1) Why drill speed matters on site
Correct drill speed improves hole quality, reduces wandering, and protects tooling. Too much RPM burns edges, work-hardens metals, and increases breakage. Too little RPM raises thrust, tears material, and can stall handheld drills. The calculator converts cutting speed into practical spindle RPM you can set confidently.
2) Cutting speed basics with useful ranges
Cutting speed is the surface distance travelled per minute at the drill edge. Typical starting values: mild steel 20–30 m/min, stainless 12–18 m/min, cast iron 18–25 m/min, and aluminum 50–90 m/min. Wood often runs higher, but control matters more than heat. Begin conservatively and increase only if chips look healthy.
3) Diameter changes everything
RPM is inversely proportional to diameter, so doubling drill size roughly halves RPM. For example, 25 m/min with a 10 mm bit yields about 796 RPM, while the same speed with a 5 mm bit yields about 1592 RPM. This scaling helps crews maintain consistent edge conditions across bit sets.
4) Feed per revolution and chip control
Feed per revolution links RPM to linear feed. Small bits and hard alloys may start near 0.05–0.10 mm/rev, while larger bits in softer metals may use 0.12–0.25 mm/rev. If chips become powdery, raise feed slightly. If the drill squeals or grabs, reduce feed or sharpen.
5) Lubrication and tool material effects
Lubrication reduces friction and heat, letting you run steadier speeds. Cutting oil often supports a modest increase in speed compared with dry drilling. Carbide tools can tolerate higher speed, but they still need stable workholding and minimal runout. In handheld work, reliability usually beats maximum speed.
6) Time, allowances, and pecking
Cycle time depends on depth, approach, and breakthrough allowances. Add approach for spotting or starting on uneven surfaces, and breakthrough for clean exit. Pecking improves chip evacuation in deep holes, but increases time. A peck factor of 1.10–1.25 is common when chip packing is likely.
7) Matching drill limits and safety
Always respect the drill’s RPM limit and torque band. High RPM with poor clamping can cause grabbing and wrist injury. If calculated RPM exceeds your tool capability, reduce cutting speed, use a larger pilot strategy, or step-drill. Stable posture, sharp bits, and correct PPE are part of the “speed” decision.
8) Masonry drilling guidance
Concrete and brick behave differently because impact energy drives removal. In masonry mode, the calculator suggests RPM by diameter, such as about 1200 RPM near 10 mm and about 900 RPM near 12–16 mm. Keep pressure consistent, clear dust, and stop if the bit overheats. Steady technique often beats higher speed.