About this calculator
The rpm that keeps the edge of the drill at the cutting speed the FAA handbooks give for the material: 200 to 300 surface feet per minute in aluminium, 30 to 50 in mild steel on the aircraft, and the general-handbook figures for harder steels, brass and plastics.
Runs in your browser. Pick the material and the drill; the common rivet drills are listed first.
How it works
rpm = cutting speed × 12 / (π × D), with the cutting speed in surface feet per minute and D in inches. The FAA Airframe Handbook gives the shop shortcut rpm ≈ CS × 4 / D, which reads about 5% higher.
Aluminium alloy 200 to 300 sfm and mild steel 30 to 50 sfm come from FAA-H-8083-31A p. 4-17. Tool or hard steel 60, alloy or cast steel 40, soft metals 300 and plastics 200 ft/min come from FAA-H-8083-30B Fig. 11-30, which also lists mild steel at 100 ft/min for machine work.
Limits — when NOT to use this
- Titanium, corrosion-resistant steel and composites are not in either handbook: use the drill or cutter maker's speeds and feeds.
- A drill motor's free speed is not its speed under load; set the speed control, then judge by the chip and the heat.
- Countersinks and reamers run slower than a drill of the same diameter: follow the tool maker's figure.
Sources
- FAA-H-8083-31A Aviation Maintenance Technician Handbook, Airframe Vol. 1, Chapter 4 — transverse pitch 75% of the rivet pitch, not under 2.5D (p. 4-35); drill speeds (p. 4-17).
- FAA-H-8083-30B Aviation Maintenance Technician Handbook, General, Chapter 11 — Figure 11-30, drill speeds by material (p. 11-22).