Browsing by Author "Enahoro, H. E."

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Flow along tool-chip interface in orthogonal metal cutting
    (College of Aeronautics, 1965-07) Enahoro, H. E.; Oxley, P. L. B.
    In recent papers it has been suggested that over part of the toolchip contact zone the chip does not slide but sticks to the tool, chip flow taking place by shear within the body of the chip. Sticking contact is inconsistent with steady state cutting and in this paper a slip-line field model of chip flow is presented which does not include sticking contact and which is consistent with the relevant experimental observations.
  • Thumbnail Image
    ItemOpen Access
    Optimisation of factors influencing the efficiency of finish machining operations
    (College of Aeronautics, 19) Enahoro, H. E.
    Optimum machining conditions were determined for various materials, steels, cast irons, brasseses, bronzes and an aluminium alloy. Surface finish readings were taken with the Sigmatex and the Surtronic and values of 10 micro-in and below were obtained at 0.001 ipr feed both under dry and wet conditions. The tests were extended to higher feeds, the maximum being 0.004 ipr; at this feed, the surface finish fell, in most cases, below 20 micro-in. it was found necessary to use high cutting speeds of the order of 800 to 1000 fpm in most cases. The most efficient tool used was a Titanium Carbide which successfully machined the whole range of test materials. The factors which were found to discourage the production of a good surface finish, given the right feed and speed, were scratching of the chip on the finished surface, bad blending of the nose radius with the two cutting edges, wrong order of grinding the flank clearance faces and the top rake face. The factors which encouraged a good surface finish were the choice of the right tool material, a suitable facet or chip deflector.
  • Thumbnail Image
    ItemOpen Access
    The relevance of the mechanics of metal cutting to machinability
    (College of Aeronautics, 1965-08) Enahoro, H. E.; Welsh, M. J. M.
    INTRODUCTION The process of metal cutting is a subject of great importance to the makers and users of machine tools. Extensive research has gone into the subject but has still left most of the phenomena unexplained. Tool life is the main interest and before any real improvement in this factor can be made, the basic metallurgical factors governing the interaction between tool and workpiece must be better understood. Such improvement can be effected through control of the wear process since both tool and workpiece are metallic and machining is a process of metal flow which is associated with a serious wear problem. The absence of exact knowledge has however hampered empirical and mathematical approaches to the problem. Basically all machining operations are considered as either oblique or orthogonal cutting, the former requiring three dimensions to specify the geometry of the cutting part of the tool and the latter two. The basic metal cutting process to be considered is that which is common, in one form or another, to all metal cutting operations using a tool, that of the wedge-shaped tool in fig. 1 (a-j) (1). Analyses of cutting have been mainly concentrated on the relatively simple case of orthogonal or two-dimensional cutting. Here the tool is so set that its cutting edge is perpendicular to the direction of relative motion between tool and workpiece and generates a plane parallel to the original work surface. In doing this the tool removes a layer of material termed the chip. One of the major objectives of metal cutting theory is the determination of machining forces, chip geometry, tool life, energy consumption and surface finish from a knowledge of the physical properties of the workpiece and tool material and the cutting conditions alone. If this could be achieved, lengthy chip measurements, delicate dynamometry, tedious and costly tool life tests and surface finish measurements might be dispensed with.