Hard turning is not a grinding process but is a process that for the correct applications can be a better alternative to Cylindrical Grinding. B and B precision offers Hard Part Turning to customers alongside conventional grinding processes so that you can choose the best solution for your requirements.

The process of turning steel with a hardness over 45 HRc (typically within the range of 55-68 HRc) is defined as hard part turning and is a cost efficient alternative to grinding. Since surface roughness of Rmax/Rz=1.6s can be achieved, hard turning is often considered a replacement for grinding operations or as a pre-grinding process.

What sort of components would benefit from hard part turning?

  • brake rotors
  • transmission gears
  • steering pinions
  • valve seats
  • pistons
  • cylinder liners
  • clutch housings

The “sweet spot” for hard turning applications are for parts that have roundness accuracy requirements between 0.8 and 12 microns, and surface roughness requirements between Rz 0.8 micron and Rz 7.0 microns.


Hard Part Turning has a number of advantages over cylindrical grinding. A turning center can complete ID turning, OD turning, taper turning, and grooving in a single chucking. It will also improve the accuracy of squareness, concentricity and straightness. Drastically reducing cycle and setup times as well.

Hard Part Turning can reduce machining time and costs by 70% or more.

Hard Turning also allows for the finishing of radius and free-curved surfaces. This is a distinct advantage over Grinding where either custom-dressed wheels (which are time consuming to produce) or highly customised grinding machines would be needed.


Grinding has the advantage of being able to achieve higher dimensional roundness and cylindricity accuracies compared with hard turning. However, since parts can typically be finished in a single chucking, hard turned parts often show superior concentricity and perpendicular characteristics to their ground counterparts. Hard Part Turning has inherent advantages over grinding but requires specific knowledge and experience that not all machinists possess.

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If you’d like to discuss your requirements with us please contact us either by email at mail@bandbprecision.co.uk or call us on +44 (0) 1484 866 386.

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