Slide 1

Cutting ToolsThe study of metal cutting is complex, due to the number of possible variables. Differences in work piece materials and cutting-tool materials, whether or not a cutting fluid is used, the relative speed of the work and cutting tool, the depth of cut, and the condition of the machine all affect the cutting operation.However, certain basic rules apply, and when you know and can apply these you will be in a better position to carry out machining operations effectively.Cutting-tool materialsRed hardness: It is obvious that a cutting tool must be harder than the material being cut, otherwise it will not cut. It is equally important that the cutting tool remains hard even when cutting at high temperatures. The ability of a cutting tool to retain its hardness at high cutting temperatures is known as red hardness.1Abrasion resistance: When cutting, the edge of a cutting tool operates under intense pressure and will wear due to abrasion by the material being cut. Basically, the harder the material the better its resistance to abrasion.2Toughness: A cutting-tool material which is extremely hard is unfortunately also brittle. This means that a cutting edge will chip on impact if, e.g. the component being machined has a series of slots and the cut is therefore intermittent. To prevent the cutting edge from chipping under such conditions, it is necessary that the material has a certainamount of toughness.34Cutting ToolsOne of most important components in machining processPerformance will determine efficiency of operationTwo basic types (excluding abrasives)Single point and multiple pointMust have rake and clearance angles ground or formed on them45Cutting-Tool MaterialsToolbits generally made of seven materialsHigh-speed steelCast alloys (such as stellite)Cemented carbidesCeramicsCermetsCubic Boron NitridePolycrystalline Diamond56Cutting OperationNever bring tool point against work that is stationaryAlways use heaviest depth of cut possible for machine and size of cutting toolNever stop machine while feed engagedWill break cutting edgeStop feed and allow tool to clear before stopping machine67Never continue to use dull cutting toolDull cutting tool recognized byWork produced oversize with glazed finishRough and ragged finishChange in shape or color of chipsApply cutting fluid only ifCan be applied under pressureCan be directed at point of cutting and kept there at all times

7Drilling MachiceDrillingDrilling is the operation of producing circular hole in the work-piece by using a rotating cutter called DRILL.

The machine used for drilling is called drilling machine.

The drilling operation can also be accomplished in lathe, in which the drill is held in tailstock and the work is held by the chuck.

The most common drill used is the twist drill.Drilling MachineIt is the simplest and accurate machine used in production shop.The work piece is held stationary i.e.. Clamped in position and the drill rotates to make a hole.

Types :-a) Based on construction:Portable, Sensitive, Radial, up-right, Gang, Multi-spindleb)Based on Feed:Hand and Power drivenSensitive Drilling MachineDrill holes from 1.5 to 15mm

Operator senses the cutting action so sensitive drilling machine

Up-Right Drilling MachineDrill holes upto 50mm

Table can move vertically and radially

Radial Drilling MachineIt the largest and most versatile used fro drilling medium to large and heavy work pieces.

Drill MaterialsThe two most common types are1. HSS drill- Low cost2. Carbide- tipped drills - high production and in CNC machinesOther types areSolid Carbide drill, TiN coated drills, carbide coated masonry drills, parabolic drills, split point drill

Drill fixed to the spindle

Drilling operations

Drilling Centre HoleDrilling Deep HolesDrilling Thin MaterialDrilling Pilot HoleTool Nomenclature

Tool Holding devicesThe different methods used for holding drill in a drill spindle areBy directly fitting in the spindle hole.By using drill sleeveBy using drill socketBy using drill chuckWork Holding Devices

Drilling operations Operations that can be performed in a drillin g machine are

DrillingReamingBoringCounter boringCountersinkingTapping

Operations in drilling machineOperations in drilling machine

Types of cuttersReamers :-Multi tooth cutting toolAccurate way of sizing and finishing the pre-existing hole. Accuracy of 0.005mm can be achieved

Boring Tool:-Single point cutting tool.Boring tool is held in the boring bar which has the shank.Accuracy of 0.005mm can be achieved.Types of cuttersCountersinks :-Special angled cone shaped enlargement at the end of the holeCutting edges at the end of conical surface.Cone angles of 60, 82, 90, 100, 110, 120

Counter Bore Tool:-Special cutters uses a pilot to guide the cutting action .Accommodates the heads of bolts.Types of cuttersCombined Countersinks and central drill :-Special drilling tool to start the hole accurately.At the end it makes countersinks in the work piece.Gun drill :-Machining of lengthy holes with less feed rates.To overcome the heating and short life of the normal drill tool

Types of cuttersTapping:-For cutting internal threadMulti cutting edge tool.Tapping is performed either by hand or by machine.Minor dia of the thread is drilled and then tapping is done.

Work Holding Devices1. Machine Table Vice

Step BlocksClampsV-BlocksAnglesJigsT- Slots Bolt

Work Holding DevicesPrecautions for Drilling machineLubrication is important to remove heat and friction.Machines should be cleaned after useChips should be removed using brush.T-slots, grooves, spindles sleeves, belts, pulley should be cleaned.Machines should be lightly oiled to prevent from rustingSafety PrecautionsDo not support the work piece by hand use work holding device.

Use brush to clean the chip

No adjustments while the machine is operating

Ensure for the cutting tools running straight before starting the operation.

Never place tools on the drilling table

Avoid loose clothing and protect the eyes.

Ease the feed if drill breaks inside the work piece.

Drilling And Drills
Types of drillsTwist drill: most common drillStep drill: produces holes of two or more different diametersCore drill: used to make an existing hole bigger

Drilling And Drills
Drilling operationsCounterboring & countersinking: produce depressions on the surface to accommodate the heads of screwsCenter drill: is a short and is used to produce the hole at the end of a piece of stockSpot drill: is used to spot (start) a hole at the desired locationGun Drilling - used fro drilling gun barrels and deep holesThrust Force and TorqueThrust force acts perpendicular to the hole axisCan cause the drill to bend or break if excessiveDrilling PracticeHeld in drill chuckswalking can be a problem when starting a holeThe drill should be guidedUsed a center drill to start a holeDrills can be reconditionedDrill life is measured by the number of holes drilled.

Drill point Geometries
Fig : Standard chisel-point drill indicating various features. The function of the pair of margins is to provide a bearing surface for the drill against walls of the hole as it penetrates into the workpiece; drills with four margins (double-margin) are available for improved drill guidance and accuracy. Drills with chip-breaker features are also available. (b) Crankshaft-point drill. (c) Various drill points and their manufacturers: 1. Four-facet split point, by komet of America. 2. SE point, by Hertel. 3.New point, by Mitsubishi materials. 4. Hosoipoint, by OSG Tap and Die. 5. Helical point.

Reaming And Reamers
Operation used to make an existing hole dimensionally more accurate than by drilling aloneThe hole making sequence isCenteringDrillingBoringreaming
Fig : various types of drilling and reaming operations.