Kazuhiro Shintani

Optimum tool geometry of CBN tool for continuous turning of carburized steel

Abstract The optimum geometry of a CBN tool for continuous turning of a carburized steel bar was determined for the angle and width of negative land, the nose radius and the honing radius. Fine turning by a tool with such an optimum geometry could be fully substituted for a grinding process on the basis of tool life and roughness of the finished surface. Tool wear as a controlling factor of tool life was analyzed. Particularly in the initial wear stage, frequent chipping of the cutting edge strongly influenced the life of tools with small negative land angles.

High Speed Machining: A Review from a Viewpoint of Chip Formation

This paper describes strong nonlinearity in log V-log L relationship, which is often found in machining of supperalloys, titanium alloys, hardened steels, cast irons, etc. The nonlinearity plays an important and favorable role in extension of life-span cutting distance at higher cutting speeds; that is, in a certain range of cutting speed, life-span cutting distance increases with cutting speed. Results of tool wear in a sliding test and cutting experiments, which showed the evidences of strong nonlinearity, were investigated and the mechanisms causing the nonlinearity were discussed.

Optimum cutting tool geometry when interrupted cutting carburized steel by CBN tool

Abstract Interrupted turning, a quite severe application for the CBN tool, was attempted. In the turning of a two-groove bar, gradual wear controlled the tool life. However tool failure determined the life in the turning of a spline shaft. The type of failure in the latter case changed depending on the way in which the tool collided with the tool tip—catastrophic damage could be avoided with substantial improvement of the tool life and surface roughness of the workpiece. For further improvements of the life, a new tool was developed having a land on the flank face. Turning with this new tool resulted in a prolonged life, as much as 26 times that of the conventional tool previously developed for continuous turning.

Microstructure and mechanical properties of sintered cubic boron nitride

Etude de la microstructure et des proprietes de c-BN en vue de son utilisation comme outil de coupe

A Study on Driven-Type Rotary Cutting for Finish Turning of Carburized Hardened Steel

Recently, cutting has replaced grinding in the finish processing of hardened steel. However, tool damage is a major problem in high-efficiency operations that use high-speed cutting and high feed rate conditions instead of the present cutting conditions. Therefore, the examination of a new cutting technique that can realize high-efficiency cutting is desired. In this study, the effects and efficiency of driven rotary cutting are investigated in the finish turning of carburized hardened steel. Based on the results, flaking occurs at the cutting edge at a short cutting length of 0.2 km using single-point turning. On the other hand, even if the cutting length amounts to 1.5 km, the tool wear width without flaking is small in the case of a driven rotary tool. Additionally, the tool wear is uniformly distributed along the circumference of the cutting edge. Furthermore, based on an examination of high-efficiency processing by increasing the feed rate, it is clarified that a feed rate of 0.3 mm/rev is the optimum condition from the viewpoint of wear resistance and surface roughness. Additionally, even if the cutting length amounts to 5.0 km for this condition, the flank wear width is as small as 0.04 mm, and the tool wear progresses gradually.

Wear properties of coated ceramic tools in high speed machining of gray cast iron

The toughness of ceramic cutting tools made of silicon nitride (Si 3 N 4 ) is improving in recent years. The nose of tool, however, wears out when cutting is performed at high speed condition, and consequently the life of the tool comes to an end. In order to reduce nose wear, the effects of coating with hard materials on the resistance of the Si 3 N 4 ceramic tool to wear were investigated. Coating the Si 3 N 4 tool with TiN+TiC+Al (ON) using the chemical vapor deposition (CVD) method proved effective for reducing nose wear as compared to when it was not coated and coated with Al 2 O 3 . The nose wear of the TiN+TiC+Al (ON) -coated Si 3 N 4 tool was reduced most effectively when applied with 6-layer coating. The nose wear in the coated Si 3 N 4 tool was found to be determined by the coating in the tool land and wear end of tool. Based on the obtained knowledge described above, a novel coating method was developed in which 3-layer coating was applied to the land part of the tool, and 6-layer coating to the other part.