BIZOMAT MAKEOS · Manufacturing
Turning Cut Planner (Speed, Power, Torque, Finish and Time)
What spindle speed, power and torque does this turning cut need, what surface finish will the feed and nose radius give, and how long will it take?
Plan of a turning operation: spindle speed from cutting speed and diameter (held to the machine’s maximum), passes for the radial stock at the depth of cut, cutting force and power from the specific cutting force (as the turning power tool), spindle torque against the machine’s torque at that speed, theoretical peak-to-valley height and roughness from feed and nose radius (as the turning cusp tool), and cutting time (as the turning time tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Work diameter | mm | Starting diameter of the work. |
| Length of cut | mm | Length turned in each pass. |
| Approach and overrun | mm | Extra travel for approach and run-out. |
| Radial stock to remove | mm | Material to remove on the radius. |
| Depth of cut | mm | Depth of cut per pass. |
| Cutting speed | m/min | Cutting speed for the tool and material. |
| Feed | mm/rev | Feed per revolution. |
| Nose radius | mm | Tool nose radius. |
| Specific cutting force | N/mm² | Specific cutting force for the material at this chip thickness (your value; see the chip thickness tool). |
| Machine efficiency | % | Share of motor power that reaches the cut. |
| Spindle power | kW | Rated spindle power. |
| Largest spindle speed | rpm | Highest spindle speed of the machine (or of the chuck and work). |
| Spindle torque available at this speed | N·m | Torque the spindle can deliver at this speed (from the power-torque chart). |
| Largest roughness Ra wanted | µm | Roughness the drawing allows. |
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: Work diameter
- What it is
- The diameter of the workpiece before the first pass. The tool uses it to set spindle speed, torque and power for every pass.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 3000 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.
- Effect on the result
- For the same cutting speed, a larger diameter lowers the spindle speed and raises the torque.
- Get it right
- Enter the diameter, not the radius.
What this means: Length of cut
- What it is
- The length turned along the axis of the work in each pass.
- 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
- Cutting time rises with length.
What this means: Approach and overrun
- What it is
- The extra travel the tool makes in each pass before it reaches the work and after it leaves, added to the length of cut.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 200 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Radial stock to remove
- What it is
- The material to remove measured on the radius: half the difference between the starting and finished diameters.
- 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 6 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Radial, not diametral: removing 12 mm off the diameter is 6 mm of radial stock.
What this means: Depth of cut
- What it is
- The radial depth the tool cuts in one pass, measured square to the work surface.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 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
- Cutting force and power rise in proportion; fewer passes are needed.
- Get it right
- Radial depth, not the reduction in diameter (which is twice the depth).
What this means: Cutting speed
- What it is
- The speed of the work surface past the cutting edge, from the tool maker for the insert grade and work material.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 3000 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 and power rise in proportion until the speed limit is reached; time falls.
- Get it right
- If the speed it needs exceeds the machine maximum, the tool holds the spindle there and the actual cutting speed is lower.
What this means: Feed
- What it is
- How far the tool advances along the work for each revolution of the spindle.
- Units and format
- Enter a number in mm/rev: millimetres per revolution. The form accepts 0.000001 mm/rev to 5 mm/rev. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.25 mm/rev as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Force and power rise in proportion, roughness rises with the square of feed and time falls in proportion.
- Get it right
- Per revolution, not per minute.
What this means: Nose radius
- What it is
- The radius of the rounded tip of the insert, given in the insert designation or catalogue.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.05 mm to 10 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.8 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The theoretical roughness is inversely proportional to the nose radius.
- Get it right
- Radius, not diameter.
What this means: Specific cutting force
- What it is
- The cutting force per square millimetre of chip cross-section for this material at this chip thickness, from tool maker data or tests.
- 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
- Cutting force, power and torque rise in proportion.
- Get it right
- It depends on chip thickness; use a value for this feed, not a general figure.
What this means: Machine efficiency
- What it is
- The share of the spindle motor’s power that reaches the cut after drive and spindle losses.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 10% 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.
- Get it right
- Type a percentage (80 for 80 %), not a fraction.
What this means: Spindle power
- What it is
- The rated power of the spindle motor, from the machine data plate or manual. The power needed at the motor is compared with it.
- 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.
What this means: Largest spindle speed
- What it is
- The highest spindle speed allowed, whichever is lowest of the machine, the chuck and the workpiece limits.
- 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 4000 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Spindle torque available at this speed
- What it is
- The torque the spindle can deliver at the spindle speed of this cut, read from the machine’s power–torque chart.
- Units and format
- Enter a number in N·m: newton-metres. The form accepts 0.000001 N·m to 1000000 N·m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 150 N·m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Read it at the actual spindle speed; many lathes give much less torque at low speed in high gear.
What this means: Largest roughness Ra wanted
- What it is
- The roughest surface the drawing allows, as the arithmetic mean roughness Ra. The theoretical Ra from feed and nose radius is compared with it.
- Units and format
- Enter a number in µm: micrometres (µm, microns). The form accepts 0.000001 µm to 50 µm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3.2 µm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- The theoretical value is a best case; real finish is rougher, so leave margin.
Method and formulas
- n = 1000 v_c ÷ (π D), limited to n_max (the cutting speed then falls); passes = stock ÷ a_p rounded up.
- F_c = k_c a_p f; power = F_c v_c ÷ 60 000 ÷ η; torque = F_c D ÷ 2000 (as the turning power tool).
- Peak-to-valley R_t ≈ f² ÷ (8r); Ra ≈ f² ÷ (32r) (as the turning cusp tool).
- Time = passes × (L + approach) ÷ (f n) (as the turning time tool).
- Example: 200 m/min on 80 mm runs at 795.77 rpm and needs 6.25 kW; Ra is about 2.4414 µm and the cut takes 1.0254 min.
Limitations
- Uses the starting diameter for every pass; later passes are slightly lighter.
- Theoretical finish only; vibration, built-up edge and tool wear make it rougher.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan speeds and feeds for a turned part
- Check a heavy cut against spindle power and torque
- Choose a feed for a required finish
Who it is for
- CNC machinists
- Process planners
- Manufacturing engineers
What you get
- Spindle speed and passes
- Cutting force, power and torque
- Theoretical finish and cutting time
Interpreting the result
- Halving the feed quarters the theoretical roughness but doubles the time.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1084–1101, 1023–1030. Topic reference; no source tables or recommended settings are reproduced.
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Open the Turning Cut Planner (Speed, Power, Torque, Finish and Time) calculator