How is spindle speed calculated for a CNC endmill?

Spindle speed uses n = (Vc × 3.8197) / D, where Vc is the surface speed in m/min and D is the tool diameter in millimetres.

What is radial chip thinning and when does it apply?

When the radial width of cut is below half the tool diameter, each tooth removes a thinner chip, so the feed rate is multiplied by a chip-thinning factor kt.

How do I check the cut against my machine limits?

The calculator compares spindle speed, cutting power and tool deflection against the configured machine limits and flags the result Compliant or Review.

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CNC Feeds & Speeds Calculator

Calculate spindle speed, feed rate, and material removal for milling and turning operations.

Workpiece & Tool Setup

Workpiece materialVc 300 m/min · fz 0.050 mm/tooth · kp 0.011

Tool material

Coating

Operation mode

High-efficiency milling, light radial and deep axial passes.

Tool diameter

Flute count

flutes

Radial width of cut (ae)

Axial depth of cut (ap)

Tool stickout length

Live Readouts

Compliant

Spindle speed134rpm

Feed rate2.72in/min

Chip thinning1.667×

Removal rate0.091in³/min

Cutting power0.02hp

Deflection0.000in

Spindle134 / 24,000 rpm

Power0.02 / 20.12 hp

Deflection0.000 / 0.002 in

Cut Engagement

ae 0.047 · ap 0.709 in

Tool deflection0.000 / 0.002 in

Stickout 1.417 in · D⁴/L³ indicator

Worked Formula

Step 1n = (Vc × 3.8197) / Dn = (420.0 × 3.8197) / 12.00n = 134 rpm
Step 2F = n × z × fz × ktF = 134 × 4 × 0.0776 × 1.667F = 69.2 mm/min
Step 3MRR = ae × ap × FMRR = 1.20 × 18.00 × 69.2MRR = 1.49 cm³/min
Step 4P = MRR × kpP = 1.49 × 0.011P = 0.02 kW

Hardware BOM

3 lines · 3 units

Item	Specification	Qty
12.0 mm 4-flute endmillEM-12-4F	Carbide · AlTiN · Adaptive HEM	1 ea
Aluminium 6061-T6 stockALUMINIUM-6061	6061-T6 · 18.0 mm depth of cut	1 ea
Tool holderBT30-ER20	Stickout 36.0 mm · 12.0 mm shank	1 ea

CNC Feeds & Speeds Presets

12 presets