BIZOMAT MAKEOS · Manufacturing
Face Milling Power Plan (Teeth, Chip Thickness, kc, Spindle Power)
How many teeth should my face mill have for this cut, what specific cutting force applies at the actual chip thickness, and does the spindle have the power?
Plan for a face milling cut: the number of teeth for the teeth wanted in the cut (as the milling cutter teeth tool), spindle speed and table feed, the engagement angle and mean chip thickness and the specific cutting force corrected for it (as the chip thickness and kc tool), and metal removal rate, cutting and motor power and torque (as the milling power tool), against the spindle power.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Cutter diameter | mm | Diameter of the face mill. |
| Width of cut | mm | Width of the surface being milled. |
| Depth of cut | mm | Axial depth of cut. |
| Teeth wanted in the cut | How many teeth you want cutting at once for smooth cutting. | |
| Teeth on the cutter (0 = suggested) | Teeth on the cutter you have; 0 uses the suggested number. | |
| Cutting speed | m/min | Cutting speed. |
| Feed per tooth | mm | Feed per tooth. |
| Lead (entering) angle | ° | Entering angle of the inserts (90° square shoulder, 45° face mill). |
| kc1.1 (specific force at 1 mm chip) | N/mm² | Specific cutting force of the material at 1 mm chip thickness. |
| Exponent mc | Chip-thickness exponent of the material. | |
| Effective rake angle | ° | Effective rake angle of the inserts. |
| Machine efficiency | % | Efficiency of the spindle drive. |
| Available spindle power | kW | Spindle motor power. |
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.
What this means: Cutter diameter
- What it is
- The diameter of the face mill measured across its cutting edges; it sets the spindle speed and the engagement angle.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 125 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Width of cut
- What it is
- The width of material the cutter engages across (radial width of cut); the tool assumes the cutter is centred on the surface.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80 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: Depth of cut
- What it is
- The axial depth of cut: how deep the cutter removes material in one pass, measured along the spindle axis.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 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 and power rise in direct proportion to the depth of cut.
What this means: Teeth wanted in the cut
- What it is
- The number of teeth you want cutting at the same time for smooth cutting, used to suggest a tooth count for the cutter.
- Units and format
- Enter a plain number with no unit. The form accepts 0.5 to 10. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- It sets the tooth count only when teeth on the cutter is 0; otherwise it is used just for the teeth-in-cut warning.
What this means: Teeth on the cutter (0 = suggested)
- What it is
- The number of teeth (inserts) on the face mill you will actually use; zero lets the tool use the suggested number.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 200. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Table feed, removal rate and power rise in proportion to the teeth on the cutter.
- Get it right
- Enter 0 to use the suggested number; the table feed and power are calculated with this count.
What this means: Cutting speed
- What it is
- The surface speed at the cutting edges, from the insert maker’s recommendations for the work material.
- 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 200 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Spindle speed, table feed and power rise in proportion to cutting speed.
What this means: Feed per tooth
- What it is
- The distance the work advances for each tooth that passes, from the insert maker’s data.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.15 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter feed per tooth, not per revolution; the tool multiplies by the teeth and the spindle speed.
What this means: Lead (entering) angle
- What it is
- The angle between the cutting edge and the direction of feed, set by the cutter body; 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.
- Get it right
- A smaller entering angle thins the chip, which raises the specific cutting force the tool calculates.
What this means: kc1.1 (specific force at 1 mm chip)
- What it is
- The specific cutting force of the work material for a chip 1 mm thick and 1 mm wide, from the tool maker’s material tables.
- 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.
What this means: Exponent mc
- What it is
- The exponent describing how the specific cutting force rises as the chip gets thinner, from the same material table as kc1.1.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 1. 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.
What this means: Effective rake angle
- What it is
- The effective rake angle of the inserts as mounted in the cutter; the tool lowers kc by one percent per degree of positive rake.
- Units and format
- Enter a number in °: degrees of angle. The form accepts -30° to 30°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Negative rake raises kc in the same way; check the sign in the insert maker’s data.
What this means: Machine efficiency
- What it is
- The share of motor power that reaches the spindle after drive losses, from the machine maker.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 1% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Lower efficiency raises the motor power needed for the same cut.
What this means: Available spindle power
- What it is
- The power the spindle motor can deliver at the working speed, from the machine’s power curve.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 10000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Check the power at the spindle speed being used; many spindles give full power only above a base speed.
Method and formulas
- Teeth = 6.3 D ÷ W × teeth in cut ÷ 2 (as the milling cutter teeth tool); n = 1000 v_c ÷ π D; table feed = f_z × z × n.
- Engagement φ = cos⁻¹(1 − 2 a_e ÷ D); mean chip h_m = 360 f_z sin κ a_e ÷ (π D φ); k_c = k_c1.1 h_m^(−m_c)(1 − γ ÷ 100) (as the chip thickness and kc tool).
- Q = a_e a_p v_f; P_c = a_e a_p v_f k_c ÷ 6×10⁷; motor power = P_c ÷ efficiency (as the milling power tool).
- Example: a 10-tooth cutter at 509.3 rpm feeds 763.94 mm/min; k_c = 2,997 N/mm² and the cut needs 11.448 kW.
Limitations
- Symmetric face milling with the cutter centred on the width.
- k_c data from the tool maker or handbook for the material.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a face mill and feed for a machine’s power
- Check heavy roughing on a small spindle
- Explain why thin chips need more power per cm³
Who it is for
- Machinists
- CNC programmers
- Process planners
What you get
- Suggested teeth and spindle speed
- Engagement, mean chip thickness and kc
- Removal rate, power and torque
Interpreting the result
- Reducing feed per tooth thins the chip and raises k_c, so power falls less than the feed does.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 808–809, 1084–1101. 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.
Method explained here · BIZOMAT original book
Holding against cutting forces
In Magnetic Workholding by the Numbers
What it covers: Compare a magnet's sliding resistance with milling forces: cutting force from power and speed, peak factors, friction with and without coolant, stops, and vacuum and clamp alternatives.
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.
Open the Face Milling Power Plan (Teeth, Chip Thickness, kc, Spindle Power) calculator