BIZOMAT MAKEOS · Manufacturing
Finish Turning Set-up (Feed for Finish, Nose-Radius Compensation, Time)
What feed gives my surface finish with this insert nose radius, how much does the nose radius distort a chamfer or taper if not compensated, and how long is the finishing pass?
Set-up of a finish-turning pass: the feed for a target Ra from the nose radius (as the feed for finish tool) or the Ra of a feed you choose, spindle speed from the cutting speed held to the machine maximum, cutting time for the pass (as the turning time tool), and the Z and X compensation and the profile error for a chamfer or taper at your angle if nose-radius compensation is not used (as the nose radius compensation tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Nose radius | mm | Nose radius of the finishing insert. |
| Ra wanted | µm | Surface roughness the drawing requires. |
| Feed chosen (0 = feed for the target) | mm/rev | Feed you intend to program; 0 uses the feed for the target Ra. |
| Cutting speed | m/min | Cutting speed for finishing. |
| Finished diameter | mm | Diameter being finished. |
| Length turned | mm | Length of the finishing pass. |
| Approach and overrun | mm | Extra travel for approach and run-out. |
| Largest spindle speed | rpm | Highest spindle speed. |
| Chamfer or taper angle | ° | Angle of the chamfer or taper to the axis that the tool also cuts. |
| Largest uncompensated profile error | mm | Largest error on the chamfer or taper you accept without nose-radius compensation. |
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: Nose radius
- What it is
- The radius of the rounded tip of the finishing insert, given in its catalogue designation. It shapes the feed marks left on the surface.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.05 mm to 5 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
- A larger nose radius lowers Ra at a given feed; the feed for the target rises with its square root.
- Get it right
- Type the radius, not a diameter.
What this means: Ra wanted
- What it is
- The arithmetic mean roughness the drawing calls for on the finished diameter. The tool finds the feed that should just give it.
- Units and format
- Enter a number in µm: micrometres (µm, microns). The form accepts 0.05 µm to 50 µm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.6 µm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use Ra, not Rz or Rt; they are different measures and not interchangeable.
What this means: Feed chosen (0 = feed for the target)
- What it is
- The feed per spindle revolution you intend to program for the finishing pass. Type 0 to use the feed that just gives the target Ra.
- Units and format
- Enter a number in mm/rev: millimetres per revolution. The form accepts 0 mm/rev to 2 mm/rev. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 mm/rev as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Theoretical Ra rises with the square of the feed; cutting time falls in proportion.
- Get it right
- This is feed per revolution, not feed per minute.
What this means: Cutting speed
- What it is
- The surface speed of the work past the cutting edge for the finishing pass, taken from the insert maker’s data for your 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 250 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Higher speed raises spindle speed and shortens the pass, until the spindle reaches its maximum.
- Get it right
- Type metres per minute, not metres per second.
What this means: Finished diameter
- What it is
- The diameter of the surface being finished. The tool uses it to turn cutting speed into spindle speed.
- 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 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the diameter, not the radius.
What this means: Length turned
- What it is
- The axial length of the finishing pass along the diameter, from the start of the cut to its end.
- 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 80 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Approach and overrun
- What it is
- The extra axial travel at feed rate before the tool reaches the work and after it leaves it. It is added to the turned length for the time.
- 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.
- Get it right
- Count both the approach and the run-out.
What this means: Largest spindle speed
- What it is
- The highest spindle speed you will allow for this job: the machine limit, or a lower limit set by the chuck or workholding.
- 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.
- Get it right
- Use the lower of the machine and workholding limits.
What this means: Chamfer or taper angle
- What it is
- The angle to the spindle axis of a chamfer or taper that the same tool also cuts. It sets the nose-radius compensation in Z and X.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 0° to 90°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 45° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Measure the angle to the axis, not to the face.
What this means: Largest uncompensated profile error
- What it is
- The largest form error on the chamfer or taper you accept if tool nose radius compensation is not used. It comes from the drawing tolerance on that feature.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 5 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.05 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Exceeding it only gives a warning to switch compensation on; it does not change the feed.
Method and formulas
- Ra ≈ 0.0316 f² ÷ R (in µm with f and R in mm × 1000), so f = √(Ra R ÷ 31.55) (as the feed for finish tool); R_t = f² ÷ 8R.
- n = min(1000 v_c ÷ π D, n_max); time = (L + approach) ÷ (f n) (as the turning time tool).
- For angle θ: ΔZ = r [1 − tan(θ ÷ 2)], ΔX = r [1 − tan((90° − θ) ÷ 2)]; profile error = r (sin θ + cos θ − 1) (as the nose radius compensation tool).
- Example: Ra 1.6 µm with r 0.8 mm needs 0.20141 mm/rev; the pass takes 15.348 s; uncompensated, the 45° chamfer is off by 0.33137 mm.
Limitations
- Theoretical finish; vibration, built-up edge and wear make it rougher.
- Straight chamfers and tapers; arcs need full compensation.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set feeds for a finishing pass
- Check a chamfer error before enabling compensation
- Estimate finishing time
Who it is for
- CNC machinists
- CNC programmers
- Process planners
What you get
- Feed for the target and Ra at the feed used
- Spindle speed and finishing time
- Nose-radius compensation and profile error
Interpreting the result
- A larger nose radius allows a higher feed for the same finish but raises cutting forces and chatter risk.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1125–1131, 782–790. Topic reference; no source tables or recommended settings are reproduced.
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Open the Finish Turning Set-up (Feed for Finish, Nose-Radius Compensation, Time) calculator