Selecting the right PCBN grade in finish hard turning

Usually wear resistance (hardness) and toughness are used to describe the characteristics of an insert. For continuous machining, wear resistance is needed, but in interrupted machining, the wear resistance has to be balanced with a certain amount of toughness, to withstand the interruptions.

For a component with both continuous and interrupted cuts, two different inserts should be used to get the best performance. The more wear resistant grade does not have enough toughness for the interrupted cut, and the tougher grade does not have enough wear resistance for the continuous cut.

This means that it is important to select the right grade for the operation. Selecting the wrong grade will seriously affect the tool life. In continuous hard turning of a gearbox gear, a customer was using a CBN-grade for heavy interrupted turning. Tool life was low, and the customer wanted improvements.

After analysing the application and the existing machining conditions, we decided to use CBN060K, a grade developed for continuous hard turning. We did not do any changes to the cutting data.

By selecting the right grade for the application, tool life was increased by over 3 times.

Always try to understand the application, and if the right insert/grade/edge preparation is used. If a crossover table had been used in this case, we would have proposed CBN160C, a grade for interrupted machining, and this would not have given the improvement we now got.

For more information, please contact your local Seco representative, or our Advanced material (PCBN/PCD/CERAMIC) team.

Henrik Sandqvist
SECO TOOLS Shanghai CO., Ltd. Level 2, Building 8, 456 HongCao Rd., Shanghai 200233, China
Office: +86 21 5426 5849
Mobile: +86 186 167 90063

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