How do I calculate drilling RPM?

RPM = (surface speed x 1000) / (pi x drill diameter), with surface speed in metres per minute and diameter in millimetres. In inch units it is RPM = (SFM x 3.82) / diameter in inches. Smaller drills must run faster to hold the same surface speed.

What feed rate should a drill use?

Feed rate = feed per revolution x RPM. Feed per revolution scales roughly with drill diameter, from about 0.05 mm/rev on a 1 mm drill to 0.30 mm/rev and above on a 20 mm drill. Check the drill maker's chart for the exact figure - too light a feed polishes and work-hardens stainless, too heavy a feed breaks small drills.

How does rigid tapping set the feed rate?

In rigid tapping the feed rate is locked to the spindle, so feed per revolution equals the thread pitch. Feed rate = RPM x pitch. The machine's feed override must stay at 100 percent while a rigid tap is in the hole or the tap will strip the thread.

Why does peck drilling take longer than the calculated cutting time?

Each peck retracts the drill clear of the hole and plunges back in, and those moves are not cutting. With a peck depth of one third of the hole depth you lose roughly two extra traverse-and-return moves per hole. The calculator adds that overhead so the cycle time is closer to what the machine actually does.

Drilling & Tapping Calculator

Work out spindle speed, feed rate and cycle time for drilling and rigid tapping, including the extra time the peck retract cycle costs. Change any input and the result updates in your browser.

Operation

Material

Diameter (mm)

Hole depth (mm)

Feed / rev (mm)

Peck depth (mm)

0 = single plunge.

Surface speed override (m/min, blank = material default)

Calculated locally in your browser. Reference values only — confirm against your tooling maker's data before a production run.

Result

Surface speed— Spindle speed— Feed rate— Material removal rate— Cutting time— Cycle time (with retract)—

RPM = (Vc × 1000) ÷ (π × D). Feed = feed/rev × RPM (drilling) or pitch × RPM (tapping). MRR = π/4 × D² × feed/rev × RPM. Peck overhead adds one retract-and-return per peck.

Copy-ready text

Reference

Starting feed per revolution by drill diameter

Drill diameter	Feed / rev (mm)	Peck depth	Note
1 – 3 mm	0.03 – 0.08	1 × D	Peck at or below one diameter to clear chips
3 – 6 mm	0.08 – 0.15	1 – 1.5 × D	Watch runout; a 4 mm drill is easily snapped
6 – 12 mm	0.12 – 0.22	1.5 – 2 × D	The common range in fixture plates and housings
12 – 20 mm	0.20 – 0.35	2 – 3 × D	Check spindle torque and coolant delivery
20 mm and up	0.30 +	2 – 3 × D	Consider insert drills or pilot plus open out

Depth-to-diameter ratio matters as much as diameter. Beyond about 4 × D, chip evacuation governs the process and the peck depth should come down. In stainless and titanium, keeping the drill cutting rather than rubbing is what prevents work hardening and premature failure.

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Basis & references: NIST — Machining and metrology data · ASME B94.11M — Twist drills · ISO 529 — Short machine taps and hand taps

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