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1、4.3 Hole making machine tool and cutting tool,Drilling machine (钻床) Boring machine (镗床) Broaching machine (拉床),Usually used hole making machine tools,Usually used hole making cutting tools,Twist drill (麻花钻) and “massesdrill” (群钻) Core drill (扩孔钻) Reamer (铰刀) Boring cutter (镗刀) Broaching cutter (拉刀),
2、4.3.1 Drilling machines,Drilling machines and boring machines can both enlarge and finish cutting of holes from a small fraction of a millimetre to hundreds of millimetres in diameter.,Drilling machines are used for rough drilling holes. Main types: Vertical(立式） 、Radial（摇臂）、Deep hole drills（深孔）. The
3、 picture shows a typical Vertical Drilling machines.,Radial drill press,Methods of Machining operations,Fig 3.29,4.3.1 Drilling machines,4.3.2 Boring machine,Boring is the operation that enlarges a pre-existed internal hole. Several machines have been developed that are specially adapted to boring w
4、ork. .,Main types of boring machines:Horizontal boring machine 、Jig boring machines and high accurate boring machine,Boring machine (镗床),Performance: big size, high accurate, different surfaces, high accurate relative position.,Main motion: rotation of the boring cutterfeed motion: cutter or workpie
5、ce,Jig boring machine (坐标镗床）: Very high accurate position.,position accuracy is between 0.0020.01mm,Diamond boring machine diamond boring cutters used.,Jobs done by horizontal boring machine,Method of Horizontal boring machine operations,4.3.3 Drilling tools,(1) Twist drill,Tip angleformed by two pl
6、anes parallel with the two main cutting edges Chisel edgecenter edge linking the two main cutting edges,The main geometry for twist drill are: the helical angle (2430)螺旋角, the tip angle 2(118130)锋角, rake angle 前角, relief angle 后角 and Chisel edge angle横刃斜角 Lip relief angle 钻缘后角,Cutting performances a
7、ffected by geometry,Helical angle: it is the axial rake angle,f,for standard twist drill =18 30。 drill bronze or soft copper： =10 17 light alloy, red copper： =35 40 high strength steel, cast iron =10 15,Tip angle,Cutting edge length,Unit cutting edge force and axial force,Tip strength,Twist moment,H
8、eat off,Tool life,1 Ordinary Twist drills（麻花钻）,The main geometry for twist drill are:the helical angle (2430), the tip angle 2(118130), rake angle , relief angle and wedge inclination angle,Different types of twist drills adapted,2 Adapted twist drills,The quality of surface machined by twist drill,
9、The accuracy: IT11-IT12 The roughness: 5012.5m The range of diameter machined: 0.180mm Material:,2 Adapted twist drillMasses Drill,Question: what are the main disadvantages of traditional twist drill ?What changes happened on “qun zuan”,三尖七刃锐当先，月牙弧槽分两边，外刃再开分屑槽，横刃磨低窄又尖。,(2) Center drill (中心钻）,Center
10、drill is used to machine the center hole of a workpiece. Fig 3.38 shows two kinds of center drilling .,center drilling,(3) Deep hole drilling (gun drilling,深孔钻),Definition of deep hole: When L/d is between 520 Method :lengthen the twist drill When L/D is bigger than 20, Method:Specialized deep hole
11、drilling machine Accuracy: usually reach IT8-IT10, sometimes IT6-IT9(Special design) Roughness: 3.20.8 m,(4) core drill(IT10-IT11,Ra6.33.2)（扩孔钻）,Accuracy: IT10-IT11 Roughness:6.33.2 m Size: 10 80mm,(5) Counter boring drill (锪钻）,(6) Reamer(IT6IT11,Ra 1.6-0.2) 铰刀,Fig structure and geometrical paramete
12、rs of reamer,The accuracy with reaming can reach IT6IT8, the roughness can be 1.60.4 m, suitable for finish or semi-finish machining,Discussion: Why can the reaming method improve the machined qualities?,various reamers,various reamers,(7) boring tool,Advantage: simple, easy to make, general purpose
13、, often used Can you tell the disadvantage?,Double blade boring tool,Material: Floating type: why? Accuracy: IT6-IT7 Roughness:can be 0.8 m Question: compared to single type, what are the main advantages of double blade boring tool?,Fig 3.46 examples for various broaching surface,(8) Broaching cutte
14、r,Discussion: could you tell the advantage of broaching method? What is the disadvantage?,structure of hole broaching cutter,Discussion: why can the broaching method achieve high accuracy ?,1head(头部)；2neck(颈部)；3cone transition (过渡圆锥)；4 frond leading part(前导部) 5 cutting part (切削部)；6 calibrating part(校准部)；7rear leading part(后导部)；8tail (尾部),Broaching layer by layer (分层拉削）,Broaching block by block (分块式拉削）,Broaching by mixing two methods (综合式）,