A Study of Economical Machining : An Analysis of the Maximum-Profit Cutting Speed

Apart from the conventional theory of the minimum-cost or maximum-production cutting speed, a new concept of the machining conditions for maximizing the profit for the manufacturing enterprise was presented

A Design of a Three-Component Tool Dynamometer

A new three-component tool dynamometer was designed. It consists of an elastic disc which is supported at its periphery. A cutting tool is installed in the center of the disc. Strain gages are attached to the disc for the force measurements. The three components of a cutting force are measured independently without any interference among them. It was found from the experimental results that this tool dynamometer has sufficient sensitivity, rigidity, and stability for practical use. This tool dynamometer is very simple in shape, and its characteristic was analyzed theoretically. The best position for the strain gages was determined, and nomographs were prepared for the design of tool dynamometers of this type

A Study on the Residual Stress Produced by Metal Cutting

Residual stresses of machined surface are caused by the mechanical effect and the thermal effect associated with cutting process. Those two effects have been analyzed theoretically using the Finite Element Method and related to X-ray test results of residual stress of carbon steel surface produced by orthogonal cutting

Machinability of Free-cutting Leaded Steels

The machinability of free-cutting leaded steel was investigated from the view-point of tool life, surface finish, cutting force and chip formation. Orthogonal and conventional cutting tests were performed for nine grades of leaded steel and four grades of non-leaded steel in order to determine the effect of including lead in steel. The addition of lead to steel was found effective in improving the machinability. The cutting mechanism of free-cutting leaded steels was analysed based upon the flow region concept. The effects of depth of cut and lead content on the cutting process were discussed. It was found that a smoother shear deformation occurs in the cutting process for leaded steels than for non-leaded steels, and hence the inclusion of lead in steels improves machinability

Behavior of Oxide-layer Adhered on Tool Surface when Machining Ca-Deoxidized Steel

Machining of Ca-Si deoxidized, Fe-Si deoxidized and conventionally deoxidized steels was investigated in order to reveal the effect and mechanism of the tool surface layer consistnig of oxides and sulfides in preventing tool wear. The tool surface layers were surveyed by the electron probe X-ray micro-analyzer, and the structural components of the layer were identified in this study. The following concludions were obtained : When machining Ca-Si deoxidized or Fe-Si deoxidized steels, the oxides and sulfides form layers on the tool surface, which avoid the direct contact of the work iron with the tool carbides, prevent the diffusion of the tool material. When cutting Ca-Si deoxidized steels, a semitransparent layer forms preferably on carbide tools which contain TiC, and it consists of 2 to 3 CaO-Al₂O₃-SiO₂. In the case of Fe-Si deoxidized steels, an ashy-grey coloured layer forms preferably on ceramic tools and it consists of CaO, Al₂O₃, SiO₂ and MnS

An Analysis of the Mechanism of Orthogonal Cutting

The orthogonal cutting mechanism with the transitional deformation range (i.e the “flow region” which exists between the rigid region of workpiece and the plastic region of steady chip), instead of the conventional shear plane, is analyzed theoretically in the case in which simple continuous chip is produced under the assumption of a perfectly plastic solid. Using the results, the experimental data for lead and brass are discussed. The theoretical expressions derived thereby can be reasonably applied to a wide range of cutting conditions, and also to the cases associated with quasi-continuous and discontinuous types of chip without any contradiction. In all cases the starting boundary-line of flow region is situated under the conventional shear line, and the ending boundary-line above it. The inclination angles of both boundary-lines and the sector angle of flow region increase with rake angle. With an increase of depth of cut, the inclination angle of starting boundary-line increases, while that of ending boundary-line and, hence, the sector angle increase for lead, but decrease for brass. Furthermore, the strain of chip based on the cutting state with a flow region is much smaller than the conventional shear strain based on the cutting state with a single shear plane. The strain of chip decreases with an increase of rake angle, and it has a tendency to decrease slightly for lead and increase gradually for brass with an increase of depth of cut

On the Cutting Mechanism for Soft Metals

By orthogonal dry cutting of soft metals such as lead and Lipowitz alloy in low velocity with a specially designed cutting test equipment, the authors recognized the existence of the transitional region (to be called the "flow region" in this paper) between the rigid region of the workpiece and the plastic region of the steady chip and it should be taken into consideration in the theoretical analysis of cutting mechanism instead of the single shear plane. ln this case the connecting line between the uncut surface of the workpiece and the back side of the chip is round. The flow region associated with a simple continuous chip changes in shape and size according to cutting conditions, and sometimes periodically under the same cutting condition. One of the most important factors affecting the size of the flow region seems to be the cutting velocity : the higher the velocity, the narrower becomes the flow region because of the localization of flow. Also in the case of a discontinuous chip, there exists a flow region during formation of one chip fragment. A fracture appears to occur on some surface near the ending boundary in the flow region where it is the easiest to slip, and is convex upwards. Then, taking this range into consideration, the deformation figures of grid lattice are drawn by deriving the general expression of chip deformation under some assumptions. Further, the authors have observed the square grid deformation under the machined surface ; that is, the grid lines formerly perpendicular to the uncut surface are bent somewhat exponentially to the cutting direction, the degree of which is remarkable with dull cutting edges. The chip-curl phenomenon in some cases is caused by the action of stress distribution at the tool-chip interface without temperature distribution in the flow region, and in this connection the tool-chip interface length depends remarkably upon the affinity characteristics between tool- and workpiece materials

A Study of the Machinability of Metals : Effect of microstructure on cutting mechanism, tool life, and surface finish

The effect of microstructure of materials on machinability of carbon steels (S15C, S40C and SK4) was investigated from the viewpoint of cutting mechanism, tool life, and surface finish. The experimental results on cutting mechanism are studied in the first half of this paper. It was found that inclination angle of the starting boundary line of the flow region was almost constant, and inclination angle of the end boundary line and the size of the flow region showed a maximum value at the lamellar portion of pearlite of 20-30%. The results obtained from the experiments on tool life and surface finish are studied in detail in the later half of this paper. The effect of spheroidized pearlite structure in high carbon steels on machinability was compared with the lamellar pearlite structure

The Effect of Cutting Fluids on Reaming Operation

In order to investigate the effect of cutting fluids on reaming operation, reaming tests were performed with various kinds of cutting fluids, and reaming torque and accuracy of reamed holes were compared for dry and wet cuttings. Tests were also made dry and wet for different cutting conditions, and effects of conditions on reaming torque and accuracy of reamed holes were investigated. Application of cutting fluids improved the accuracy of reamed holes, though reaming torque was increased. The cutting torque component was scarcely affected by cutting fluids. But cutting fluids increased the burnishing torque component in the order of dry, cutting oils, and soluble oils. Dry reaming and reaming with cutting oils produced oversized holes. Reaming with soluble oils produced smaller holes than the actual size of the reamer. The smaller the amount of enlargement of the reamed hole, the larger the burnishing torque component, and the better the surface finish in the order of dry, cutting oils, and soluble oils. With increases in cutting speed, feed, and depth of cut, the amount of enlargement increased and the surface finish of the reamed hole became worse for both dry and wet conditions. The sharp reamer showed a peculiar phenomenon for torque pattern in relation to feed rate. The stable reamer which was used several dozen times produced better reamed holes than the sharp reamer

A Study of Super-High Speed Machining

This paper is concerned with the fundamental study of super-high speed machining. Cutting tests were performed on carbon steel with carbide, ceramic, and cermet tools to investigate the fundamental problems such as tool forces, tool life, surface roughness, etc. at super-high speeds (above the conventional cutting speed) obtained easily by the latest high-speed precision lathe, and to find out the possibility of practical use of super-high speed machining in machine shops. It was found that a certain grade of the ceramic tool has a great possibility of being used for super-high speed machining. Super-high speed machining operation produced an excellent surface finish, increasing the productivity of finish operation, but the tool life at super-high speeds was short at the present stage. The development of tool materials with high heat resistance and machine tools with high rigidity enough for super-high speeds is expected. Cutting fluids supplied to super-high speed machining increased surface finish slightly, but decreased tool life