The Forming Theory and Computer Simulation of the Rotary Cutting Tools with Helical Teeth and Complex Surfaces
This paper researched the forming theory of the cutting tools with helical teeth and complex surfaces. Deduced the nonlinear equations of the movement of NC system to generate such tools, presented the way to find the solution of the equations, calculated the cross section graphics of the teeth profile and computer simulation of NC machining.
A manufacturing model of carbide-tipped spherical milling cutters
Abstract The paper presents a manufacturing model for use in grinding the front-end surfaces of a carbide-tipped spherical milling cutter. The concepts of radial equidistant lines and oblique equidistant surfaces are presented. Based upon these concepts, a model of the cutting edge of a spherical milling cutter is derived by solution for the intersection of the spherical front-end surface of the cutter and the equation of a sphere. A special mechanism model is also presented for grinding the rear cutting-edge surface of the cutter. To ensure that the mechanism model is valid, the cutting-edge curve of the cutter is also on the rear cutting-edge surface. The associated geometric and manufacturing parameters are further optimized to ensure that the best quality of the carbide-tipped spherical milling cutter can be achieved. The mechanism is also used to study the manufacturability of spherical milling cutters for slightly varying specifications. A numerical example is presented to illustrate the effectiveness of the proposed modelling procedure for producing carbide-tipped spherical milling cutters. Numerical results indicate that the proposed manufacturing model and grinding procedure are capable of producing a family of carbide-tipped spherical milling cutters with an accuracy up to the user-provided specific tolerance. Some major contributions of the proposed approach are summarized in the conclusions.
The Gospel and the land;: Early Christianity and Jewish territorial doctrine,
Ostensibly Davies' patient study of the concepton of the "land" (Israel, Jerusalem) in early Christianity is an essay in Biblical theology, but he also wishes to raise serious questions about Christian understanding (or misunderstanding) of Judaism. "Christians have usually understood Judaism in too theological, and therefore, too intellectual terms. And they have also looked at their own foundation document, the New Testament, in the same way. In their proper concern to unravel theological developments and subtleties in primitive Christianity, they have neglfected to search for evidences of an encounter between it and the realia of Judaism and for any possible resolutions of such an tencounter. In particular, they have failed to inquire after the place of the land in the thought and lives of early Christians" (p. 161). Davies observes, for example, that bible dictionaries often have no references whatsoever to "land" and those that do allot it but a few pages. Even in Old Testament scholarship, where the land is of central significance in the documents themselves, it has been neglected. His work is an attempt to provide a context of Jewish thinking from early Israelite writings up to the Talmud in which to place the Christian materials. The bulk of the book is an account of the historical and theological process by which early Christianity gave a "spiritual" interpretation of traditional Jewish views of the land. Read against the Jewish background, the radical spiritualizing of the tradition is striking. Yet Davies also shows that Jewish attitudes were not monolithic in the first century, that notions of a preexistent, heavenly or eschatological Jerusalem were present, and that some Jews considered the viability of Judaism apart from the land. At some point however what could be entertained as an abstraction in Judaism, when it was made concrete in the life of the Christian movement, could not be tolerated. The conflict was heightened, of course, by the destruction of Jerusalem and the continued existence of Christianity as a movement increasingly receptive to non-Jews. Christianity, however, while rejecting the link between the land and religion, did create a new sense of "holy space" by hallowing the places where Christ had been, a development which would find fullest expression some several centuries later. As a result of the Holocaust and the establishment of the modern state of Israel Christians are faced with a whole new series of issues which have lain dormant since the destruction of Jerusalem in A.D. 70. Davies' work must be read against this backdrop to appreciate its significance. It is as much a book about modern Christian thinking as it is about the past, as many of his citations and his several appendices of speeches at Jewish-Christian conferences show. To some it may appear that he has sided too closely with certain strands of Judaism and allowed this to color his way of handling the pre-Christian and pre-Rabbinic material, but such criticism is carping. Much of the material here is gathered together in this fashion for the first time, and he has successfully shown that a major preoccupation of ancient Judaism is missing in contemporary biblical scholarship. Further, he has given us a moving yet scholarly statement of the pathos of the modern Christian who cares about Christ and Israel and who tries to understand Israel while loving Christ.