【文章內(nèi)容簡介】 Tool features have been identified by many names. The technical literature is full of confusing terminology. Thus in the attempt to clear up existing disorganized conceptions and nomenclature, the American Society of Mechanical Engineers published ASA Standard B5221950. what follows is based on it. A singlepoint tool is a cutting tool having one face and one continuous cutting edge. Tool angles identified in Fig. 142 are as follows: (1) Backrake angle, (2) Siderake angle, (3) Endrelief angle (4) Endrelief angle (5) Siderelief angle (6) Endcuttingedge angle, (7) Sidecuttingedge angle, (8) Nose angle, (9) Nose radius. Tool angle 1, on front view, is the backrake angle. It is the angle between the tool face and a line parallel to the base of the shank in a longitudinal plane perpendicular to the tool base. Then this angle is downward from front to rear of the cutting edge, the rake id positive。 when upward from front to back, the rake is negative. This angle is most significant in the machining process, because it directly affects the cutting force, finish, and tool life. The siderake angle, numbered 2, measures the slope of the face in a cross plane perpendicular to the tool base. It, also, is an important angle, because it directs chip flow to the side of the tool post and permits the tool to feed more easily into the work. The endrelief angle is measured between a line perpendicular to the base and the end flank immediately below the end cutting edge。 it is numbered 3 in the figure. It provides clearance between work and tool so that its cut surface can flow by with minimum rubbing against the tool. To save time, a portion of the end flank of the tool may sometimes be left unground, having been previously forged to size. In such case, this endclearance angle, numbered 4, measured to the end flank surface below the ground portion, would be larger than the relief angle. Often the end cutting edge is oblique to the flank. The relief angle is then best measured in a plane normal to the end cutting edge perpendicular to the base of the tool. This clearance permits the tool to advance more smoothly into the work. The siderelief angle, indicated as 5, is measured between the side flank, just below the cutting edge, and a line through the cutting edge perpendicular to the base of the tool. This clearance permits the tool to advance more smoothly into the work. Angle 6 is the endcuttingedge angle measured between the end cutting edge and a line perpendicular to the side of the tool shank. This angle prevents rubbing of the cut surface and permits longer tool life. The sidecuttingedge angle, numbered 7, is the angle between the side cutting edge and the side of the tool shank. The true length of cut is along this edge. Thus the angle determines the distribution of the cutting force. The greater the angle, the longer the tool life。 but the possibility of chatter increases. A promise must, as usual, be reached. The nose angle, number 8, is the angle between the two ponent cutting edges. If the corner is rounded off, the arc size is defined by the nose radius 9. the radius size influences finish and chatter. Cutting Tool Materials A large number of cutting tool materials have been developed to meet the demands of high metalremoval rates. The most important of these materials and their influence on cutter design, are described below. High Carbon Steel. Historically, high carbon steel was the earliest cutting material used industrially, but it has now been almost entirely superseded since it starts to temper at about 220℃ and this irreversible softening process continues as temperature increases. Cutting speeds with carbon steel tools are therefore limited to about (30ft/min) when cutting mild steel, and even at these speeds a copious supply of coolant is required. Highspeed Steel. To overe the low cutting speed restriction imposed by plain carbon steels, a range of alloy steels, known as highspeed steels, began to be introduced during the early years of this century. The chemical position of these steels varies greatly, but they basically contain about % carbon and 4% chromium, with addition of tungsten, vanadium, molybdenum and cobalt in varying percentages. They maintain their hardness at temperatures up to about 600℃ , but soften rapidly at cutting speeds in excess of (350ft/min), and many cannot successfully cut mild steel faster than (150ft/min). Sintered Carbides. Carbide cutting tools, which were developed in Germany in