BIZOMAT MAKEOS · Manufacturing
Milling Cut Planner (Speed, Thinned Feed, Power and Torque)
What spindle speed and feed should I program for this milling cut, and will the machine have the power?
Milling set-up from cutter and cut data: spindle speed from cutting speed (capped at the spindle limit), feed per tooth raised to keep the target maximum chip thickness at light radial engagement, table feed and removal rate, average chip thickness and specific cutting force (Kienzle), cutting power and torque against the machine’s power, and the feed that would use full power.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Cutter and cut | ||
| Cutter diameter | mm | Cutter diameter. |
| Number of teeth | Teeth (inserts) on the cutter. | |
| Cutting speed | m/min | Recommended cutting speed for the tool and material. |
| Target maximum chip thickness | mm | Maximum chip thickness the tool maker recommends. |
| Radial engagement | mm | Radial width of cut. |
| Axial depth of cut | mm | Axial depth of cut. |
| Lead (entering) angle | ° | Lead angle of the cutting edge (90° for square shoulder). |
| Material | ||
| Specific cutting force kc1.1 | N/mm² | Specific cutting force at 1 mm chip thickness for the material. |
| Kienzle exponent mc | Kienzle exponent for the material. | |
| Machine | ||
| Maximum spindle speed | rpm | Spindle speed limit. |
| Spindle power | kW | Rated spindle power. |
| Spindle efficiency | % | Efficiency from motor to cutter. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
Cutter and cut
What this means: Cutter diameter
- What it is
- The diameter of the milling cutter measured across its cutting edges.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Number of teeth
- What it is
- The number of teeth or inserts on the cutter that cut in each revolution.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 200. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Table feed and power rise in proportion to the number of teeth.
What this means: Cutting speed
- What it is
- The cutting speed the tool maker recommends for the tool grade and work material, at the cutter’s outside diameter.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 5000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 180 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- If the spindle cannot reach the matching rpm, the tool caps the speed at the spindle limit.
What this means: Target maximum chip thickness
- What it is
- The maximum chip thickness the tool maker recommends for the cutter; the tool works back to the feed per tooth that produces it.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.1 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Chip thickness, not feed per tooth; at small radial engagement the feed is raised to reach it.
What this means: Radial engagement
- What it is
- The radial width of cut: how much of the cutter diameter is engaged sideways in the work.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- It cannot exceed the cutter diameter.
What this means: Axial depth of cut
- What it is
- The axial depth of cut, measured along the cutter axis.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 500 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Removal rate, power and torque rise in direct proportion to it.
What this means: Lead (entering) angle
- What it is
- The lead (entering) angle of the cutting edge relative to the machined surface; a square shoulder cutter has 90°.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 10° to 90°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 90° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A smaller lead angle raises the feed per tooth needed for the same chip thickness.
Material
What this means: Specific cutting force kc1.1
- What it is
- The specific cutting force of the work material at a chip thickness of 1 mm, from the tool maker’s material data.
- Units and format
- Enter a number in N/mm²: newtons per square millimetre (equal to MPa). The form accepts 0.000001 N/mm² to 10000 N/mm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1700 N/mm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Power and torque are directly proportional to it.
- Get it right
- Take kc1.1 and mc as a pair from the same material data.
What this means: Kienzle exponent mc
- What it is
- The Kienzle exponent describing how specific cutting force rises as the chip gets thinner, for the work material.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 0.6. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.25 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Machine
What this means: Maximum spindle speed
- What it is
- The highest spindle speed the machine allows, which caps the speed worked out from the cutting speed.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 12000 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Spindle power
- What it is
- The rated power of the spindle motor, which the power needed for the cut is compared with.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 1000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 11 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- It does not change the power needed; it sets the pass or fail check and the feed for full power.
What this means: Spindle efficiency
- What it is
- The efficiency of the spindle drive from motor to cutter, which turns cutting power into motor power.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 30% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 85% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power needed is inversely proportional to it.
- Get it right
- Type the percentage itself, not a fraction.
Method and formulas
- n = 1000 V_c ÷ π D (capped at the spindle limit).
- Below half-diameter engagement f_z = h_ex D ÷ [2√(a_e (D − a_e))] ÷ sin κ; otherwise h_ex ÷ sin κ.
- v_f = f_z z n; MRR = a_e a_p v_f; engagement angle φ = arccos(1 − 2a_e ÷ D); h_m = 360 f_z sin κ a_e ÷ (π D φ).
- k_c = k_c1.1 h_m^(−mc); P = MRR k_c ÷ 60×10⁶ ÷ η; feed for full power ∝ (P_max ÷ P)^(1 ÷ (1 − mc)).
- Example: a 50 mm, 4-tooth cutter at 180 m/min runs at 1,145.9 rpm and 572.96 mm/min, using 3.1707 kW.
Limitations
- Average power; peak torque on few-tooth cutters is higher.
- Material constants and tool recommendations come from the tool maker.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Program a new milling cut quickly and safely
- Check whether a roughing cut fits the spindle power
- Raise feed for light radial cuts without overloading
Who it is for
- Machinists
- CNC programmers
- Manufacturing engineers
What you get
- Spindle speed, feed per tooth and table feed
- Chip thickness, removal rate and power
- Torque and full-power feed
Interpreting the result
- If spindle power limits, reduce axial depth before feed; feed per tooth controls tool life and finish.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1084–1101, 1162–1167. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · Library collection
Milling cutters and milling strategies: speeds, feeds, chip thickness and parts that are easy to mill
What it covers: How milling works, the main cutter types, climb versus conventional milling, calculating speed and feed, chip thinning, adaptive toolpaths, chatter and design rules that make milled parts cheaper.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
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