Tool Life Extension Methods for Cut-off Tools Made of High-speed Steel

The paper presents tool life extension methods applied to cut-off tools made of high-speed steel. Despite the wide application of cutting tools made of sintered carbides, which is becoming the main cutting material, including the coated tools, there still remain the applications of high-speed steel cutting tools for low cutting speed machining (i.e. screw taps, reamers, broaching tools, cutting off tools). Therefore the improving of their cutting ability is important to be researched. The paper involves the application of selected modification methods for the increasing of the tool life in operating conditions, i.e. in manufacturing of ball bearing rings from the bar raw product. Moreover, the paper introduces and evaluates the results obtained by individual methods (tool mechanical and physical modifications) finding the reasons of longer tool-lives for example by analysing the metallographic microsections of chip formation process.