The change of tool life in a wide range of cutting speeds in hard turning

J. Kundrák, Zoltán Pálmai

Research output: Contribution to journalArticle

1 Citation (Scopus)


Tool life changes according to a curve presenting two extreme values depending on the cutting speed. Besides the well-known Taylor formula, several other functions describe tool life, mainly for the 3 rd speed range beginning with a tool-life maximum. In earlier studies the authors suggested a tool-life function valid for the whole speed range. Here the machinability of hardened steel is being investigated in a wide range of cutting speeds. The intention of this study is to work out a method for the physical interpretation of tool degradation defining the tool life. For this purpose the nonlinear differential equation of wear rate is applied. During the experimental work the tool life was measured when boring a 100Cr6 hardened workpiece of 75 mm diameterin the speed range v c =10...120 m/min with a feed rate of f=0.075 mm/rev, depth of cut a p =0.1 mm, γr=-5° and the life criterion W cr =0.4 mm. The results proved the supposition that at a speed smaller than the tool-life maximum it is abrasion and adhesion that causes the tool deterioration, while above this speed, the thermo-activated degradation process plays an increasingly large role as speed increases. Calculating from the results of the cutting examination, the activating energy of the degradation process is Q=136±29 KJ/mol, on the basis of which it is likely that the degradation of the tool material occurs through the recrystallization of the surface layer from cubic into hexagonal, causing the surface layer to wear out more rapidly.

Original languageEnglish
Pages (from-to)254-260
Number of pages7
JournalManufacturing Technology
Issue number2
Publication statusPublished - Jan 1 2019



  • Hard turning
  • PCBN tool
  • Tool-life function
  • Wear equation

ASJC Scopus subject areas

  • Industrial and Manufacturing Engineering

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