9Bench Drilling Machine Located generally on the work benchUsed for small jobs, also called as sensitive drilling machine.Used for drilling small and medium sized holes (up to 15mm ).Consists of a round column with a rigid base fastened to the benchHas a work holding table and an arm mounted on the round columnArm carries the drill spindle on one side and the drive motor on the other sideA stepped cone pulley with V – belt is used to transmit the power from motor to spindleDept. of Mech & Mfg. Engg.
10Bench Drilling Machine The work table can be moved up and down to suit the required job height and can be locked at suitable heightThe table can rotate about its axis by 360°Drilling operation is performed by fixing the job properly on the work tableDrill bit is gradually fed by rotating hand feed lever towards the work pieceOnce the required depth of cut is completed, the feed lever is rotated in the opposite direction to withdraw the tool from the work.Dept. of Mech & Mfg. Engg.
11Radial Drilling Machine Dept. of Mech & Mfg. Engg.
12Radial Drilling Machine Radial drilling machine is used for medium and heavy duty applicationsConsists of a heavy, circular column mounted on a very strong baseRadial arm that can swing around is mounted on the column and the radial arm can be raised and loweredDrill head with drive and feed mechanism is fitted on to the radial armDrill head can move horizontally along the guides of the arm and can be locked at any desired positionDept. of Mech & Mfg. Engg.
14Types of Drilling Machines Drilling machines may be classified asPortable drilling machine.Bench or Sensitive drilling machine.Radial drilling machine.Pillar drilling machine.Gang drilling machine.Multiple spindle drilling machine.Dept. of Mech & Mfg. Engg.
15List the operation performed on a drilling machine. The different machining operations that can be performedon a drilling machine are as follows.DrillingReamingBoring.Counter BoringCounter sinkingSpot facingTapping.Dept. of Mech & Mfg. Engg.
16Boring: Done on a drilling machine to increase the size of an already drilled holeWhen a suitable size drill is notavailable,Initially a hole is drilled tothe nearest sizeUsing a single point cuttingtool, the size of the hole isincreased to required sizeBy lowering the tool while it is continuously rotating,The size of the hole isincreased to its entire depth.Dept. of Mech & Mfg. Engg.
17Counter boring Counter bore Tool It is to increase the size of a hole at one end only through a small depthIt forms a larger sized recess or a shoulder to the exiting holeThe cutting tool will have asmall cylindrical projectionknown as pilotIt guides the toolCounter bore ToolPilotDept. of Mech & Mfg. Engg.
18Condition: Counter boring Counter bore ToolPilotCondition:Diameter of the pilot will always be equal to the diameter of the previously drilled holeCutting Speed:Two-third of the drilling speedPurpose:It is done on the hole to accommodate the socket head screw, or grooved nuts, or round head bolts.Dept. of Mech & Mfg. Engg.
19Countersinking Cutting speed Use: It is the operation of making the end of the hole into aconical shapeUsing countersinking toolMay also be employed for deburring the holesCutting speedOne - half of that used forsimilar size drillUse:When the countersunk screws are to be screwed into the holes, so that their top faces have to be in flush with the top surface of the work piece.Dept. of Mech & Mfg. Engg.
22Milling MachineMilling is a metal cutting operation in which the operating tool is a slow revolving cutter having cutting teeth formed on its periphery.The milling cutter is a multipoint cutting tool. The work piece is mounted on a movable work table which will be fed against the revolving milling cutter to perform the cutting operation.
23The difference between drilling and milling is that, in drilling a rotating drill is fed against a stationary work-piece, while in milling the work-piece is fed against a milling cutter which only revolves.Similarly, it also differs from the lathe operation because the lathe tool is fed against rotating work-piece.A milling machine is a power operated machine tool in which the work-piece mounted on moving table is machined to various shapes when moved under a slow revolving serrated cutter.
24Principle of MillingThe Figure 1 shows the principle of cutting action of the milling cutter. The milling cutter is mounted on a rotating shaft known as arbor. The work-piece which is mounted on the table can be fed either in the direction opposite to that of the rotating cutter as shown in Fig.1A or in the same direction of that of the cutter as shown in Fig.1B.
25When the work-piece is fed in the opposite direction to the cutter tooth at the point of contact, the process is called conventional or up milling.In this process, as the work-piece advances against the rotating cutter, the chip that is removed gets progressively thicker as shown in Fig.1A
26The action of the cutter forces the work-piece and the table against the direction of the table feed, thus each cutter tooth enters a clean metal gradually thus the shock load on each tooth is minimized.The disadvantage of this method is that when making deep cuts, such as in heavy slotting operations, the cutter tends to pull the work-piece out of the vice or the fixture since the cutting force is directed upward at an angle.
27When the work-piece is fed in the same direction as that of the cutter tooth at the point of contact, as shown in Fig. 1B, the process is called climb or down milling.In this process, the cutter enters the top of the work-piece and removes the chip that gets progressively thinner as the cutter tooth rotates.
28Classification of Milling Machine Generally, more metal can be removed for each cut than the conventional up milling. Climb milling is used only on materials that are free of scale and other surface imperfections that would damage the cutters.Classification of Milling MachinePlain or Horizontal Type of Milling MachineVertical Milling MachineUniversal Milling MachinePlaner Type Milling MachineProfile Cutting Milling Machine
33SHAPERThe shaper is a reciprocating type of machine tool intended primarily to produce flat surfaces.These surfaces may be horizontal, vertical, or inclined.In general shaper can produce any surface composed of straight line elements.
35Ram: it holds and imparts cutting motion to the tool through reciprocation Bed: it holds and imparts feed motions to the jobHousing with base: the basic structure and also accommodate the drive mechanismsPower drive with speed and feed change mechanisms.Shaping machines are generally used for producing flat surfaces, grooving, splitting etc.Because of poor productivity and processcapability these machine tools are not widely used now-a-days for production.
37Grinding, also called abrasive machining, is a process in which the material is removed in the form of fine chips, almost as dust particles by the abrasive action using some kind of abrasive materials.The thickness of the material chips removed by grinding ranges from 0.25 to 0.50 mm in finishing and general grinding operations.Abrasive is the mineral material employed for sharpening, grinding and polishing operations
38The two types of abrasives used are; natural and artificial. The examples of natural abrasives are emery, corundum, quartz. sandstone, diamond, etc.The important properties of abrasives are, hardness, toughness, uniformity in grain sizes, and sharpness.
39Grinding wheel Terminology GritThe grit is the grain size of the abrasive grain.The grain size is expressed as a number. Thus, coarse grain size can be between 10 and 24, Medium grain size can be between 30 & 60, Fine grain size can be between so and, very fine grain size can be between 220 and 600.
40GradeGrade is the hardness of the bond, which is designated by alphabets. The letter "A" Stands for very soft material and the letter " Z" stands for very hard grade.Wheel structureThe abrasive grains are distributed over the abrasive wheel in a structural form. The wheel structure is also represented as a number. For example, Dense can be from 1 to 8 and Open can be from 9 to 15.
41Bond typeIt is denoted by alphabets like V is for vitrified Bond, B is for Resinoid, R is for Rubber, E is for shellac and S is for silicate, and so on.AbrasiveAbrasives are denoted by alphabets-Example: A stands for Aluminum oxide & C Stands for Silicon Carbide.