Mn-Zn (Manganese-Zinc) ferrite polycrystals have been widely used as a core material of magnetic heads in video cassette recorders or floppy disk drives of personal computers. In this research, slot grinding was performed to investigate the chipping generation mechanism at slot edge of Mn-Zn ferrite polycrystal with metal bonded diamond wheels. A high precision slicing machine with an air spindle of low friction and low thermal expansion was used. After grinding, the chippings at a slot edge was measured by means of a form tracer with a knife edge tip, and analyzed with a newly developed measurement method using a personal computer under various grinding conditions. On the other hand, by means of SEM observation, a material removal mechanism at the edge of Mn-Zn ferrite was investigated. The results are follows. Pre-process, such as lapping, before grinding can reduce chipping size. Most of chipping is generated by transgranular fracture. As chipping size depends on the removal per grain; qw=α·μ2 (Vw/Vs), a decrease in removal qw, chipping size after slot grinding could be reduced.

This paper describes the effect of the motion of diamond grains on the material removal rate and surface roughness in the lapping of Mn-Zn polycrystalline ferrite using a Sn lapping plate and 0.3μm diamond abrasives. The diamond grains can be classified into fixed and loose grains. The grains fixed to a lapping plate were confirmed by SEM and AFM observations. Among many experimental parameters, the change of the pitch of fine grooves on a lapping plate formed by the facing operation has a significant effect on the removal rate. This agrees well with the calculated number of loose grains under various pitches of groove. The average removal rate with fixed and loose grains was found to be about 2.7 times higher than that with only fixed grains. These results indicate that during lapping, the material is mainly removed by loose grains. It is evident from AFM images that the lapped surface with material removed by fixed grains differs very much from that with material removed simultaneously by fixed and loose grains.

In this research, a snag grinding was performed on a 410 stainless steel with two different alumina wheel types under constant load, using a specially made grinding machine. The variation of grinding characteristics such as metal removal rate and grinding force with the progress of grinding has been studied. On the other hand, the protrusion height and wear flat area of abrasive grains on the working surface of wheel were measured to discuss the results obtained on grinding characteristics. A close correlation was found among the variation of abrasive protrusion height, metal removal rate and tangential grinding force. Also, it was known that the wear area of grains increases with increasing grinding time. The attritious wear was accompanied with reductions of metal removal rate and tangential grinding force. Self-sharpening recovered the abrasive protrusion height and diminished the percent wear flat; this enhanced to improve the metal removal rate and a cutting action by an individual abrasive grain.

The machining of grinding wheel is an important research problem related to wheel finishing process. This subject is also a typical example of ceramic composite material machining. However, there is insufficient information about this type of cutting. In this study, a turning experiment was performed on white alumina grinding wheels by the use of cemented carbide, sintered CBN and sintered diamond single point cutting tools. The cutting speed ranged from 0.003 to 150 m/min, the maximum depth of cut was 1.0 mm, and the feed was 0.6 mm/rev. Thus, the tool wear and cutting force were measured for various cutting conditions, and the optimum operating condition and mechanism of chip formation were obtained. The effects of cutting speed, rake angle, and nose radius were specially investigated. The cutting mechanism was also studied from a specially low speed orthogonal cutting experiment and FFT analysis. It is evident from this study that grinding wheel can be cut easily by using a proper cutting tool, such as K01 and sintered diamond tool, and by selecting relatively low cutting speeds, great negative rake angle and large nose radius. The chip is mainly formed by compressive fracture.

In most shear angle theories in metal cutting, the relation between shear angle and other parameters, such as the mean angle of friction on tool face and the contact length between chip and tool, has been usually pursued on a steady state deformation process. But, it is difficult to make clear the reason why the steady state deformation of chip can be derived from each set of cutting conditions. In this study, an orthogonal dry cutting test was carried out using a carbide tool (P20) and diamond tool with the purpose of studying the compatibility of a machining equation. Intermittent cutting tests were also performed to study a transient chip formation. From an experimental result obtained in the cutting with a diamond tool, it was clear that the equation including the relation between shear angle and two machining parameters (rake angle and the product of cutting speed and depth of cut) is most adaptive as a machining equation. The reason why the shear angle depends on the product of cutting speed and depth of cut is as follows; the cutting temperature affects largely the chip material seizure on the tool face, and also, the thickness of secondary deformation zone. The chip material seizure and the thickness of secondary deformation zone are thought to be main causes of the variation in shear angle. As a result, it is concluded that, as temperature is approximately proportional to the product of cutting speed and depth of cut, the shear angle depends on the product of cutting speed and depth of cut.

In this study, a constant-load heavy grinding has been made using a specially designed snag grinding machine of 40 kW, where plate workpiece was used to keep pressure constant. The 455 mm dia. resinoid wheels were used for the experiment, and a 1 m long steel plate of different widths was used for workpiece. Thus, the effects of load, traverse speed, wheel width, work-piece width, and wheel type on grinding performance have been studied from standpoints of removal rate, wheel wear, G-ratio, and grinding force. It is evident that if load is identical the removal rate, as well as wheel wear rate, is always the same independently of wheel width or workpiece width. The ZS wheel is the best from a standpoint of stock removal, while the SR wheel showed the highest G-ratio. A wider workpiece causes higher tangential force for a given removal rate, while wheel width does not affect the force.

In order to explain the mechanism of saw-toothed chip formation in metal cutting, it is necessary to know the deformation and fracture property of work material. In this study, the dynamic torsion test was carried out under the condition corresponding to that in the cutting experiment about the temperature rise at deformation zone. The 0.2%C steel, the 304 steel and titanium were tested at various temperature. Further, the conditions of saw-toothed chip formation were also discussed theoretically. The results obtained are as follows: (1) From the result at room temperature, the fracture strain γf for the 0.2%C steel and titanium were obtained as γf=2.0 + 0.004σ and γf=1.2 + 0.001σ, respectively, where σ is normal stress (MPa) acting on the shear plane. The mechanism of saw-toothed chip formation under the same cutting condition can be explained as the ductile fracture caused by over strain. (2) In high speed torsion tests at high temperature for the 0.2%C steel and at room temperature for the 304 steel, an unstable flow was occurred. Therefore, the mechanism of saw-toothed chip under the same condition can be explained as an unstable flow caused by thermal softening.

There are some researches on the saw-toothed chip formation, but there are many points which are uncertain. An important subject in this research is to elucidate the fracture mechanism of work material near the shear plane during cutting.

Workpiece temperature is thought to have a significant influence on the deformation mechanism in chip formation during machining metals. So, in this study, the sub-zero and high temperature cutting experiments were carried out to investigate the influence of workpiece temperature on the morphology and the forming ranges of saw-toothed chip. Besides of the SUS 304 steel and the titanium used in the previous study, in the present study, the cutting experiment was also persuaded on the 0. 2% C steel which hardly generates the saw-toothed chip on being cut. The results obtained are as follows:(1) The forming ranges of saw-toothed chip when machining the 0. 2% C steel becomes larger with increasing workpiece temperature, and on the contrary, when the SUS 304 steel is machined the range becomes smaller, and it does not change in the case of the titanium.(2) When machining the 0. 2% C steel, the pitch of shear zones decreases with increasing workpiece temperature, but it increases when machining the SUS 304 steel or the titanium.(3) The distance of slips when machining the 0. 2% C steel decreases with the increase in workpiece temperature up to 200°C, and then, increases with temperature up to 600°C. When machining the SUS 304 steel or the titanium, it does not have a definite tendency.

The saw-toothed chip on machining metals is thought to have a significant influence on the tool wear or the quality of finished surface. The mechanism of saw-toothed chip formation process is entirely complicate and still not understood. The present study was carried out to find the morphology and the forming ranges of the saw-toothed chip on machining metals. The SUS 304 steel, titanium, 18% Ni-maraging steel, and Ti 6 Al 4 V alloy were employed for workpiece, while the M20 sintered carbide was used for cutting tool. The results obtained are as follows : (1) The saw-toothed chip is formed at the speeds above 50 to 100m/min on machining the SUS 304 steel, above 10 to 50 m/min for machining the maraging steel, and between0.1to 500m/min for both the titanium and the Ti6A14V.(2) The pitch of shear zones, as well as the distance of slips, are of the same order as the depth of cut, and these increase in the order of the maraging steel, Ti 6 Al 4 V, titanium, and SUS 304 steel.(3) The rake angle has a little effect on the relation of cutting speed vs. pitch of shear zones, but a great effect on the relation of cutting speed vs. distance of slips.(4) The pitch of shear zones increases proportionally with the depth of cut, but it increases with cutting speed when machining the titanium and decreases when machining the SUS 304 steel.