B&B Precision Engineering | Huddersfield


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Our Experts On Hard Part Turning

Here at B&B Precision our experts are working hard coming up with new, better solutions for our customers. One of our favourite things is teaching customers about new techniques that can improve their end product or save them money.

Hard Part Turning is a fantastic alternative to Cylindrical grinding, and for the right component can have some great advantages. 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.

Good For…

What sort of components would benefit from hard part turning?  Typical parts are brake rotors, transmission gears, steering pinions, valve seats, pistons, cylinder liners and 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. Our client Sandvik says it 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 perpendicularity characteristics to their ground counterparts.

Hard Part Turning gives has inherent advantages over grinding but requires specific knowledge and experience that not all machinists possess. Although it will save you money in the long run, the initial investment in CBN inserts is pretty steep.

This is why hiring experts like B&B can help you test the waters and reduce your costs further, and knowing that experts are taking care of it means a faster and worry free production chain.

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