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Precision Machining Utility • Milling, Turning & Drilling

CNC Feed Rate Calculator

Compute exact linear table feed rates from spindle RPM, flute count, and tooth chip load. Features forward and reverse calculations with metric and imperial unit conversion.

End mills, face mills & CNC routers

RPM

Spindle rotational speed in revolutions per minute (RPM).

flutes

Total number of active cutting teeth or flutes on the cutter.

mm/tooth

Target material thickness removed by each cutting tooth per revolution.

mm
Primary Calculated Result✓ VERIFIED RESULT
Feed Rate
600mm/min
Compensated Feed Rate:750 mm/min
Chip Thinning Factor (RCTF): 1.25x20% stepover
■Machining & Performance Parameters
Feed / Rev
0.2 mm/rev
Spindle Speed
3,000 RPM
Chip Load
0.05 mm/tooth
Cutting Speed
94.2 m/min
Material Removal Rate
6 cm³/min
Estimated Cycle Time
2 min min
How This Was Calculated
Feed Rate (F) = RPM × Number of Flutes (Z) × Chip Load (fz)
3,000 RPM × 4 flutes × 0.05 mm/tooth
= 600 mm/min

Machining Safety Notice: Calculated values are theoretical mathematical starting points and not guaranteed safe machining parameters. Actual feeds and speeds depend heavily on machine rigidity, spindle power, workholding stability, tool material and coating, workpiece alloy hardness, coolant application, and vibration characteristics. Always consult tooling manufacturer catalog recommendations before running parts on CNC equipment.

Understanding CNC Feed Rate Mechanics

In CNC machining, feed rate represents the linear travel speed of the cutting tool across or into the workpiece along programmed axes (X, Y, or Z). Achieving the correct feed rate is critical to balancing metal removal rate, tool wear life, surface finish, and cutting forces.

Milling Feed Rate Formula

In rotating multi-tooth milling, feed rate is a direct product of spindle rotational speed, active cutting flutes, and target chip load per tooth:

F = RPM × Z × fz
  • F: Table Feed Rate (mm/min or IPM)
  • RPM: Spindle rotational speed (rev/min)
  • Z: Number of cutting flutes on the tool
  • fz: Chip load per tooth (mm/tooth or IPT)

Turning & Drilling Formula

In lathe turning and hole drilling, tool advancement is governed per full rotation of the workpiece or spindle:

F = RPM × fn
  • F: Linear Feed Rate (mm/min or IPM)
  • RPM: Spindle rotational speed (rev/min)
  • fn: Feed per revolution (mm/rev or IPR)

Worked Step-by-Step Calculation Examples

Metric Example (End Mill)

Machining 6061-T6 Aluminum with a 10 mm 3-flute carbide end mill running at 8,000 RPM with a recommended chip load of 0.06 mm/tooth:

F = 8,000 RPM × 3 flutes × 0.06 mm/tooth
= 1,440 mm/min
Imperial Example (Face Mill)

Facing 4140 steel with a 3.0 inch 5-insert indexable face mill at 650 RPM with a catalog feed of 0.005 IPT:

F = 650 RPM × 5 inserts × 0.005 IPT
= 16.25 IPM
MACHINING TOOLKIT

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FAQ & MACHINING REFERENCE

Feed Rate Frequently Asked Questions

What is feed rate in CNC machining?

Feed rate is the linear velocity at which the cutting tool advances through or along the workpiece. In milling, it is measured in millimeters per minute (mm/min) or inches per minute (IPM). In turning and drilling, feed is often expressed as feed per revolution (mm/rev or IPR).

How do you calculate CNC milling feed rate?

Milling feed rate is calculated using the formula: Feed Rate = Spindle Speed (RPM) × Number of Flutes (Z) × Chip Load per Tooth (fz). For example, a 4-flute end mill running at 3,000 RPM with a chip load of 0.05 mm/tooth produces a feed rate of 3,000 × 4 × 0.05 = 600 mm/min.

Why does feed rate differ between milling, turning, and drilling?

In milling, multiple cutting edges rotate past the material, distributing the cut across multiple teeth. In turning, a single stationary insert contacts the rotating part continuously, so table advancement is governed by feed per revolution. In drilling, feed rate is also programmed per full spindle revolution rather than per tooth.

What happens if my CNC feed rate is set too slow?

If the feed rate is too low relative to RPM, the cutter teeth rub and burnish rather than cleanly shear the workpiece. This generates extreme friction and thermal wear, dulling cutting edges rapidly and work-hardening austenitic materials like stainless steel.

What happens if my CNC feed rate is set too fast?

Excessive feed rate creates chip loads exceeding the cutter's flute gullet capacity and shear strength. This leads to catastrophic tool breakage, excessive tool deflection, chatter marks, and poor surface finish.