Tool Wear in End Milling Slots

Abstract

<p>This thesis records an investigation of tool wear in milling slots with carbide-tipped and high speed steel end milling cutters as well as the development of the equipment used. The study is limited to one conventional material (mild steel) and one difficult-to-machine alloy (multimet) only.</p> <p>The first four chapters present a general review of machinability of materials, description of tool materials and various mechanisms of tool failure. Discussion of problems related to the machinability of heat resistant alloys as well as a discussion on machining under interrupted cutting conditions are included. The theories described are used in interpreting the experimental results.</p> <p>The fifth chapter describes the development of a Quick-Stop Device. This device is used in metal cutting research to rapidly reduce the velocity of the cutting tool relative to the workpiece to zero. The device enables investigations to be made of the geometrical and metallurgical behaviour of the chip as it is born.</p> <p>In Chapter VI the effect of various cutting conditions on the development of the tool wear while end milling steel as well as multimet is analyzed and optimum cutting conditions for end milling the two materials are recommended.</p> <p>In order to try to explain some of the phenomena observed. Turning experiments simulating previous milling operations were carried out and are described in Chapter VII. Here it was possible to separate the aspects of thin and thick chips from the aspects of interrupted cutting. The results of these tests indicate that the thin portion of the chip obtained at the entry and exit of end milling cutter affects tool life much less than the thick part of the chip. However, even these tests did not explain why it was rather the total number of cut interruptions than the actual cutting time which influenced tool life. Further research will be necessary in looking into both the mechanical and thermal shock aspects.</p>