【切2.后角，这是机加工面与被称为后面。的分区其主云顶环机加上面的摩擦和增列 般采用5广6°的后角 (D)pi (1)间新切属 列连切 (③)带切屑瘤的连续切屑 rmented chip parates into short pieces,which may or may not adhere runs ahead of the tool. 间断切屑：分段的切屑分散成小碎片，既可能相互附若也可能不相互附若。在靠近切削面处发生金属的剧烈 变形，导致在运动刀具前方金屈层产生裂缝 Eventually,the shear stress across the chip becomes equal to the shear strength of the material,resulting in fracture and separation.With this type of chip,there is little relative movement of the chip along the tool face,Fig.7.3a. 最后，横过切屑的剪切应力与材料的剪切强度相等，造成断裂和分离。生成这类切屑时，切屑沿刀具面几乎没有相 对运动，见图7.3a。 Continuous chip.The continuous chip is characterized by a general flow of the separated metal along the tool face.There may be some cracking of the chip,but in this case it usually does not extend far enough to cause fracture 连续切屑： 续的切屑 般具有分离金属沿刀具面流动的特征。切屑可能有一些破裂，但在这种情况下切屑 通常不会延长到足以引起断裂 nere to tne too. ne con Ontinuous chip usually shows a good cutting ratio and tends tends 种切屑形成于用较 的物 速度机加 的向。连续切通常具有良好 率和趋 生最适宜的表面光洁 危险 1图 chip hows the existence of a localized,highly deformed zone of 带切屑瘤的连续切周：这种切屑显示了粘合或“焊接在刀具面上材料局部高度变形区的存在。 that this built is held in by the static until it be o large that the exterr on it se it to disl with some of it remaining on the machined surface and the rest passing off on the back side of the chip. 实际上，对显微照片的分析显示这种切屑受到静摩擦力抑制直至它变得大到作用在它上面的外力使其移动，一些 留在机加工表面上而另一些延伸到切屑的背面，见图7.3c。 Cutting Fluids切削液 The functions of cutting fluids (which are often erroneously called coolants)are: To cool the tool and workpiece To reduce the friction 切削液（经常误称为冷却液）的功能如下： 冷却刀具和工件 减少摩擦 To protect the work against rusting To improve the surface finish To prevent the formation of built-up edge To wash away t the chips from the cutting zone 保护工件不生 改善表面光洁度 刻 3 2. 后角：这是机加工面与被称为后侧面的刀具底面夹角。后角使刀具不产生会损坏机加工面的摩擦和增加 切削力。很大的后角会削弱刀尖的强度，因此一般采用 5~6°的后角。 (1) Discontinuous chip (2) Continuous chip (3) Continuous chip with BUE (Built up edge) (1)间断切屑 (2)连续切屑 (3)带切屑瘤的连续切屑 Discontinuous Chip. The segmented chip separates into short pieces, which may or may not adhere to each other. Severe distortion of the metal occurs adjacent to the face, resulting in a crack that runs ahead of the tool. 间断切屑：分段的切屑分散成小碎片，既可能相互附着也可能不相互附着。在靠近切削面处发生金属的剧烈 变形，导致在运动刀具前方金属层产生裂缝。 Eventually, the shear stress across the chip becomes equal to the shear strength of the material, resulting in fracture and separation. With this type of chip, there is little relative movement of the chip along the tool face, Fig.7.3a. 最后，横过切屑的剪切应力与材料的剪切强度相等，造成断裂和分离。生成这类切屑时，切屑沿刀具面几乎没有相 对运动，见图 7.3a。 Continuous chip. The continuous chip is characterized by a general flow of the separated metal along the tool face. There may be some cracking of the chip, but in this case it usually does not extend far enough to cause fracture. 连续切屑：连续的切屑一般具有分离金属沿刀具面流动的特征。切屑可能有一些破裂，但在这种情况下切屑 通常不会延长到足以引起断裂。 This chip is formed at the higher cutting speeds when machining ductile materials. There is little tendency for the material to adhere to the tool. The continuous chip usually shows a good cutting ratio and tends to produce the optimum surface finish, but it may become an operating hazard, Fig.7.3b. 这种切屑形成于用较高切削速度机加工有延展性的材料时。材料几乎没有粘附刀具的倾向。连续切屑通常具有良好 的切削率和趋向于产生最适宜的表面光洁度，但可能成为操作的危险之源，见图 7.3b。 Continuous with a built-up edge. This chip shows the existence of a localized, highly deformed zone of material attached or “welded” on the tool face. 带切屑瘤的连续切屑：这种切屑显示了粘合或“焊接”在刀具面上材料局部高度变形区的存在。 Actually, analysis of photomicrographs shows that this built-up edge is held in place by the static friction force until it becomes so large that the external forces acting on it cause it to dislodge, with some of it remaining on the machined surface and the rest passing off on the back side of the chip, Fig.7.3c. 实际上，对显微照片的分析显示这种切屑瘤受到静摩擦力抑制直至它变得大到作用在它上面的外力使其移动，一些 留在机加工表面上而另一些延伸到切屑的背面，见图 7.3c。 • Cutting Fluids 切削液 The functions of cutting fluids (which are often erroneously called coolants) are: • To cool the tool and workpiece • To reduce the friction 切削液(经常误称为冷却液)的功能如下： • 冷却刀具和工件 • 减少摩擦 • To protect the work against rusting • To improve the surface finish • To prevent the formation of built-up edge • To wash away the chips from the cutting zone • 保护工件不生锈 • 改善表面光洁度