Hơn nữa nó được biết đến là phổ biến ý nghĩa văn hóa và thời gian phụ thuộc, tức là một tuyên bố đó là lẽ thường ngày hôm nay không thể là một tuyên bố ý nghĩa phổ biến trong tương lai (Anacleto et al, 2006b). Ví dụ, hãy xem xét báo cáo "Mặt trời xoay quanh trái đất". Ngày nay, tuyên bố này được xem là sai, tuy nhiên, hàng trăm năm trước người dân được sử dụng tin rằng đó là đúng. Một ý tưởng có thể để chuyển khó khăn này là để xây dựng cơ sở tri thức hợp tác bởi. | 2 Turning and Chip-breaking Technology Machines are the produce of the mind of Man and their existence distinguishes the civilized man from the savage WILLIAM COBBETT 1762-1835 Letter to the Luddites of Nottingham 34 Chapter 2 Cutting Tool Technology In the following sections a review of a range of Turning-related technologies and the importance of chipbreaking technology will be discussed. Turning - Basic Operations Turning can be broken-down into a number of basic cutting operations and in effect there are basically four such operations these are 1. Longitudinal turning Fig. 16a 2. Facing Fig. 16b 3. Taper turning - not shown 4. Profiling - not shown. NB These turning operations will now be very briefly reviewed. In its most simple form turning generates cylindrical forms using a single-point tool Fig. . Here a tool is fed along the Z-axis slideway of the lathe CNC or a turning centre while the headstock rotates the workpiece . the part is held in either a chuck on a mandrel face-plate or between centres - when overhang is too long machining the component and thereby generating a circular and cylindrical form of consistent diameter to the turned part1. Facing is another basic machining operation that is undertaken Fig. 16b and in this case the tool is fed across the X-axis slideway while the part rotates again generating a flat face to the part or a sharp corner at a shoulder alternatively it can be cutting the partial or finished part to length facing-off 2. Taper turning can be utilised to produce short or long tapers having either a fast taper . with a large included angle or slow taper . having a small included angle - often a self-holding taper such as a Morse taper . There are many different operations that can be achieved on a CNC lathe turning centre 1 The range of turning operations is vast feedrates can be varied as can rotational speeds. 2 Facing operations can also be used to produce either curved convex or concave surface
