BIZOMAT MAKEOS · Manufacturing
Turning Cusp Height
What ideal peak-to-valley cusp follows from feed and nose radius?
Compare exact circular-nose turning cusp geometry with the small-feed approximation.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Axial feed per revolution | mm/rev | Actual straight-turning axial feed per revolution, not feed per minute. |
| Circular nose radius | mm | Circular nose radius from the insert geometry, not a wiper effective width. |
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: Axial feed per revolution
- What it is
- The distance the tool moves along the part for each revolution of the spindle in straight turning. It sets the spacing between neighbouring tool marks.
- Units and format
- Enter a number in mm/rev: millimetres per revolution. The form accepts 0 mm/rev to 1000 mm/rev. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.2 mm/rev as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cusp height rises roughly with the square of feed: doubling feed gives about four times the cusp.
- Get it right
- Use feed per revolution, not feed per minute; divide mm/min by rpm to convert.
What this means: Circular nose radius
- What it is
- The radius of the rounded tip of the turning insert, the circular arc that leaves the tool marks on the surface.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.001 mm to 1000 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
- Cusp height falls roughly in proportion to a larger nose radius.
- Get it right
- Read it from the insert designation or supplier data; wiper inserts do not follow this simple circular model.
Method and formulas
- Exact h = r − √(r² − f²/4). The equivalent f²/[4(r + √(r² − f²/4))] retains precision at small feed.
- Approximate h = f²/(8r). Multiply millimetres by 1000 for micrometres.
- Example: f = 0.2 mm/rev and r = 0.8 mm gives exact cusp 6.274607 µm; the approximation gives 6.25 µm.
Limitations
- Peak-to-valley geometry is not measured Ra or Rz; no surface-parameter conversion is made.
- Wiper geometry, chatter, wear, built-up edge and material recovery can dominate finish.
- Feed must be below the nose diameter; this bound does not establish a suitable cutting setting.
- Default values are worked examples, not recommended settings or material properties.
Typical uses
- turning finish geometry
- nose radius
- peak-to-valley cusp
Who it is for
- Machinists
- Process engineers
What you get
- Exact ideal cusp in micrometres
- Small-feed approximation
- Approximation difference
Interpreting the result
- Compare geometric trends, then measure the specified surface parameter.
- Check tool data and stability before changing feed or nose radius.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 733–742. Topic reference; implementation and examples are original, and no source tables are reproduced.
- Method: circular-segment geometry. Handbook pages explain surface-texture terminology, not guaranteed finish.
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