BIZOMAT MAKEOS · Manufacturing
Cutting Speed or Feed for Full Machine Power
How fast can this cut run before it uses all the available spindle power?
Highest cutting speed (turning) or table feed (milling) that uses the available spindle power for a given depth, feed or width of cut and specific cutting force.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Operation | choice | Turning or milling. |
| Available spindle power | kW | Spindle power available at the speed you will run (from the machine power curve). |
| Machine efficiency | % | Overall efficiency from motor to cutting edge. |
| Specific cutting force kc | N/mm² | Specific cutting force for the material at your chip thickness (tool supplier data). |
| Depth of cut (axial in milling) | mm | Depth of cut (turning) or axial depth (milling). |
| Feed (turning) | mm/rev | Feed per revolution (turning). |
| Workpiece diameter (turning) | mm | Work diameter, to give the spindle speed (turning). |
| Width of cut (milling) | mm | Radial width of cut (milling). |
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: Operation
- What it is
- Whether the cut is turning, where the tool finds the highest cutting speed, or milling, where it finds the highest table feed rate the power allows.
- Units and format
- Choose one of 2 options from the list: Turning; Milling.
- Example
- The form opens with “Turning” selected as a worked example. Choose the option that matches your case.
- Get it right
- Feed and workpiece diameter are used only for turning; width of cut only for milling.
What this means: Available spindle power
- What it is
- The spindle motor power available at the speed you will run, read from the machine’s power curve or manual.
- 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 11 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The maximum speed or feed and the removal rate are directly proportional to power.
- Get it right
- Many spindles deliver less than rated power at low speed; use the value at your speed.
What this means: Machine efficiency
- What it is
- The share of motor power that reaches the cutting edge after losses in belts, gears and bearings, from the machine maker or your own measurement.
- 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
- The maximum speed or feed and the removal rate are directly proportional to efficiency.
- Get it right
- Type the percentage itself, not a fraction: 80 for 80 %.
What this means: Specific cutting force kc
- What it is
- The specific cutting force: the cutting force per square millimetre of chip cross-section for this work material at your chip thickness, from tool supplier 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 2000 N/mm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The maximum speed or feed and the removal rate are inversely proportional to kc.
- Get it right
- Use the value for your chip thickness, as kc rises for thin chips; N/mm² is the same as MPa.
What this means: Depth of cut (axial in milling)
- What it is
- The depth of cut: in turning, how far the tool cuts into the radius; in milling, the axial depth along the cutter axis.
- 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 4 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The maximum speed or feed is inversely proportional to the depth of cut.
- Get it right
- In turning this is the radial depth per side, not the change in diameter.
What this means: Feed (turning)
- What it is
- How far the turning tool advances along the work in one revolution of the spindle.
- Units and format
- Enter a number in mm/rev: millimetres per revolution. The form accepts 0.000001 mm/rev to 10 mm/rev. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.3 mm/rev as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The maximum cutting speed is inversely proportional to feed.
- Get it right
- Per revolution, not per minute. Used only for turning.
What this means: Workpiece diameter (turning)
- What it is
- The diameter of the workpiece where it is being cut, used to turn the maximum cutting speed into a spindle speed.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The spindle speed at the power limit is inversely proportional to this diameter.
- Get it right
- Used only for turning. It changes the spindle speed, not the cutting speed limit.
What this means: Width of cut (milling)
- What it is
- The radial width of cut in milling: how much of the cutter diameter is engaged across the work, measured square to the cutter axis.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 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.
- Effect on the result
- The maximum table feed is inversely proportional to the width of cut.
- Get it right
- Used only for milling; in full slotting it equals the cutter diameter.
Method and formulas
- Turning: vc = P η × 60 000 ÷ (kc ap f) (m/min); n = 1000 vc ÷ πD.
- Milling: vf = P η × 60 × 10⁶ ÷ (ae ap kc) (mm/min).
- Removal rate at the limit = P η × 60 000 ÷ kc (cm³/min) for either operation.
- Example: 11 kW at 80% with 4 × 0.3 mm in kc 2000 allows up to 220 m/min.
Limitations
- The tool supplier’s speed limit and the machine’s speed and torque limits may be lower than the power limit.
- kc changes with feed and tool wear.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan the fastest roughing cut a machine can take
- Find whether a cut is power-limited or tool-limited
- Compare machines for a job
Who it is for
- Machinists
- CNC programmers
- Manufacturing engineers
What you get
- Maximum cutting speed and spindle speed (turning)
- Maximum table feed and removal rate (milling)
Interpreting the result
- Run at the lower of the power-limited and tool-recommended values, with a margin for wear.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1084–1101. Topic reference; no source tables or recommended settings are reproduced.
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