Shape-Compliant Chucks maintain accuracy of existing features

Patent-pending, Super-Precision Hydraulic Shape-Compliant Chucks support the maintenance of high accuracy roundness on thin-wall hardened and out-of-round parts. The Chucks have been designed primarily for ‘finish’ turning operations on thin-walled hardened parts – but they also can be used to maintain concentricity, accuracy etc on softer, more delicate and fragile parts too. In the case of a heat-treated bearing race (60-64 Rockwell) with intended distorted inside diameter (ID) and outside diameter (OD) characteristics (therefore out-of-round), using a conventional Step Chuck to achieve the finished roundness on the part created problems. In essence, the gripping forces acting on the workpiece caused it to become round. When released, the workpiece sprung back to its previous out-of-round shape, but because deformation has occurred due to the combined gripping forces and spring-back action the original roundness and concentricity were lost. In comparison, the Shape Compliant Chucks enable the part to be gripped ‘as is’ in its out-of-round shape which means that after release the original out-of-round dimensions are protected and maintained. The Chuck does this by gripping the part at multiple locations (radial positions) with equal force – the Chuck also centres the part. In this OD gripping case study, test results using the Hardinge Chuck delivered a significant improvement in maintaining out-of-roundness during and after the finishing cutting process. The end result being – greater accuracy, improved process reliability, reduced scrap and/or re-working. Shape-Compliant chucks are not ‘off-the-shelf’ workholding solutions – they are manufactured to order (application-specific) by Hardinge according to individual customer requirements… and take into account a number of machining variables – applied force levels; operational speed range; grip points; jaw requirements; workpiece condition and accuracy required etc.