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Interpolation turning

​All machine concepts have been developed to provide multi-functional options – turning, drilling and milling operations can now be carried out in sliding head machines through to 5-axis machining centers. Turning operations have used a machine axis to rotate the part around the component’s axis of symmetry.


Symmetrical features on non-symmetrical parts have used boring tools for parallel diameters on standard machining centers. However where contours are required normally circular interpolation by milling or a W-axis head has been required to generate the form.


A new machine development called interpolation turning has been developed for advanced machining centers and B axis multi-task machines. A turning operation can be carried out by interpolating with the X and Y axis in a circular direction and rotating the machine spindle in time with the rotational contour.

The circular movement can either increase or decrease in diameter to produce facing operations or be combined with the Z axis to produce a bore or outer diameter.

This method does not compete with the metal cutting efficiency of traditional boring or turning operations, however it does provide a viable option to interpolation with milling or W-axis facing heads. It should be considered for new machines where the components have symmetrical features on non-symmetrical components – e.g flanges, seal grooves and non-parallel bores.

The limitations of the method and machines are:

  • The revolutions per minute – speed of the X, Y table feed
  • Programming support – CAM cycles/post processors
  • Spindle torque – as the spindle motor is rotating at a relatively low rpm the depth of cut of the turning operation should not be excessive
  • Spindle interface – the coupling should be capable of transmitting a higher level of torque than normally required for milling operations. Steep taper 50 or Coromant Capto have superior torque transmission than HSK-A



The pictures show the difference in table movement between interpolation turning and the traditional way.


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Main benefits with interpolation turning

  • Flexible solution, making it possible to use machining centres with modular tool set-ups instead of dedicated boring machines with W-axis facing heads
  • The component can be machined completely without moving it – especially beneficial for large non-symmetrical components
  • Reduced tool investment costs
  • The CoroBore XL bridge is available in aluminium which helps
    to keep the tool assembly weight within the machine tool
    change and magazine capability

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Tooling considerations

  • The tool radius should be kept relatively close to the component radius being cut to limit the X, Y movement – ie large component radius should have cutting tools with large radius or offset from the centre of rotation
  • Where longer profiles are needed it is good to have a tool radius larger than the spindle housing. This improves accessibility and process stability by reducing the need for long slender tools
  • The two above considerations lead to larger tool diameters and torque so at the same time it is important to
    • ensure the tool weight, moment and diameter keep within the capability of the magazine and tool changer
    • the motor and spindle interface can cope with the torque demands


Tooling solutions

Existing modular concepts are combined to provide tailored solutions for the requirements of interpolation turning – each having its position depending upon the component feature diameter and geometry.

  • Axial Coromant Capto quick change clamping units with CoroBore XL slide interface for axially mounted cutting units and clearance of the spindle housing. Available in sizes C4 and C5 for diameters up to 1275 mm (50 inch)


  • Machine interface adaptors combined with Coromant Capto turning cutting units for internal as well as external features
  • Coromant Capto offset reduction clamping units provide clearance and increased tool radius for tool overhang up to 4 times the boring bar adaptor tool.


  • Silent Tools dampened boring bars with SL cutting units for deep boring applications from 6 to 10 times the boring bar diameter


  • SL70 adaptors and blades held in machine interface adaptors provide a large offset and clearance for profiling


  • SL40 cartridges and integrated slides for CoroBore XL allow large diameter tools to be built for clearance of the spindle housing 


  • Radial Coromant Capto clamping units to provide larger offset




How to order

Parts are to be ordered separately.


Size J, K, L – diameter 147–300 mm (5.79–11.8 inch)
Coromant Capto C4

Items needed:

  • 1 Adaptor (Size J, K or L)
  • 1 Slide: S17-R820XLC4QC-080
  • 1 Cover plate: S17-820XL-CP

Check turning catalogue for complete assortment of cutting units


Size M, N, O – diameter 300–1275 mm (11.8–50.2 inch)
Coromant Capto C5 

Items needed:

  • 1 Bridge (Size M, N, O)

  • 1 Slide: S24-R820XLC5QC-095

  • 1 Cover plate: S24-820XL-CP

Check turning catalogue for complete assortment of cutting units  



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