Turning, Drilling & Milling

Feed per Revolution Calculator

Calculate feed per revolution (IPR or mm/rev) from table feed rate and spindle speed. Essential for CNC lathes, drilling operations, and multi-flute milling feeds.

UNITS:

OD turning, boring & facing

Solve For

Primary Calculated Result✓ VERIFIED RESULT

Feed / Rev

0.15mm/rev

How This Was Calculated

Feed per Revolution (fn) = Feed Rate (F) / RPM

180 mm/min / 1,200 RPM

= 0.15 mm/rev

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.

Feed per Revolution (fn) in Modern CNC Machining

Unlike chip load per tooth which divides cut advance across multiple milling teeth, feed per revolution (fn) measures tool advance per complete 360° spindle turn.

Turning & Drilling Formula

Solve for feed per revolution from programmed linear feed rate and spindle RPM:

fn = Feed Rate / RPM

For example, a lathe programmed at 180 mm/min at 1,200 RPM has a feed per rev of 180 / 1200 = 0.15 mm/rev.

Milling Multi-Tooth Relationship

In milling cutters, feed per revolution is the sum of chip loads for all active teeth:

fn = Z × fz

A 4-flute end mill with 0.05 mm/tooth chip load advances 4 × 0.05 = 0.20 mm per revolution.

Surface Finish Cusp Height Calculation

In turning, feed per revolution determines the scallop/cusp height left on the turned diameter. Theoretical peak-to-valley height (Rmax) is calculated by:

Rmax ≈ fn² / (8 × rε)

Where fn is feed per revolution and rε is the insert corner radius. Halving the feed per revolution reduces cusp height by 75%, vastly improving turned surface finish.

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FAQ & MACHINING REFERENCE

Feed per Revolution Questions & Answers

What is feed per revolution (IPR / mm/rev)?

Feed per revolution (fn) is the linear distance a cutting tool advances along its path for each complete 360-degree rotation of the spindle. It is the fundamental feed parameter for lathe turning, boring, threading, and drilling.

How does feed per revolution differ from feed per tooth (chip load)?

In milling, multiple teeth engage sequentially, so feed per tooth (fz) is the cut thickness per tooth. In turning, a single tool cuts continuously, so feed per revolution directly equals the advance rate per rotation. In milling, Feed/Rev = Number of Flutes × Chip Load.

How do you calculate feed per revolution from feed rate?

Feed per revolution is calculated by dividing table feed rate by spindle RPM: fn = Feed Rate / RPM. For example, 180 mm/min / 1,200 RPM = 0.15 mm/rev.

How does feed per revolution affect lathe surface finish?

In lathe turning, surface roughness (Ra) is directly proportional to the square of feed per revolution and inversely proportional to tool nose radius: Ra ≈ fn² / (32 × Corner Radius). Decreasing fn or increasing nose radius produces a smoother surface finish.