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Chapter 23Chapter 23Machining Processes Used to Produce Round Shapes:

Turning and Hole Making

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ProcessesProcesses

Turning (outside surface)• straight, taper, facing, contour, form, cut-off,

threading, knurlingBoring (internal holes)• taper, form, drilling, threading, reaming

Drilling (internal)Reaming (internal)

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Machining Surface RoughnessMachining Surface Roughness

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Drilling HolesDrilling Holes

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“Drilling” Operations“Drilling” Operations

Various types of drills and drilling and reaming operations.

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Drilling VideoDrilling Video

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Drilling MachinesDrilling Machines

Figure 23.24 (a) Schematic illustration of the components of a vertical drill press. (b) A radial drilling machine. Source: (b) Courtesy of Willis Machinery and Tools.

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Various Types of DrillsVarious Types of Drills

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DrillsDrills

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ReamersReamers

Figure 23.26 (a) Terminology for a helical reamer. (b) Inserted-blade adjustable reamer.

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General Capabilities of DrillingGeneral Capabilities of Drilling

Feed, fSpeed, VDepth of cut, dDiameter, DRPM, N

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Speeds and Feeds in DrillingSpeeds and Feeds in Drilling

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Drilling Design ConsiderationsDrilling Design Considerations

Design for clampingFlat surfaces preferredTolerances requirementsMachinability of materialsAllowance for toolDepth of hole (walking)Diameter of hole

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Boring Process CharacteristicsBoring Process Characteristics

Single point toolEnlarges or straightens an existing holeProduces accurate holes (better tolerances than drilling)Able to produce large internal holesCan be performed on a lathe, boring mill, or jig bore machine tools

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BoringBoring

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Boring and Boring MillBoring and Boring Mill

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Boring Design ConsiderationsBoring Design Considerations

Through holes, not blind holesGreater length to diameter more difficultAvoid intermittent cuts

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Turning ProcessTurning Process

Creates cylindrical external or internal shapesCreates flat surfaces on part ends (faces)Uses a single point toolWide variety of shapesThe machine tool is called a “lathe”

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Lathe CAD VideoLathe CAD Video

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Video – Lathe/TurningVideo – Lathe/Turning

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Lathe Cutting Operations Lathe Cutting Operations Turning: produces straight, conical, curved, or grooved workpieces

Facing: produces flat surfaces at the end of the part and perpendicular to its axis. Also used to produce grooves.

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Lathe Cutting OperationsLathe Cutting OperationsParting or Cutting Off: cuts a piece from the end of a partThreading: produces external or internal threadsKnurling: produces a regularly shaped roughness on cylindrical surfaces, as in making knobs

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Lathe Cutting OperationsLathe Cutting OperationsForm tool: produces axisymmetric partsBoring: enlarges a previous hole or to produce circular internal groovesDrilling: produces a hole

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Cutting Screw ThreadsCutting Screw Threads

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LatheLathe

Figure 23.2 General view of a typical lathe, showing various components. Source: Courtesy of Heidenreich & Harbeck.

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NC Lathe and TurretNC Lathe and Turret

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Parts Made on LathesParts Made on Lathes

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Turning OperationTurning Operation

Figure 23.3 Schematic illustration of the basic turning operation, showing depth-of-cut, d; feed, f; and spindle rotational speed, N in rev/min. Cutting speed is the surface speed of the workpiece at the tool tip.

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ToolTool

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Turning FormulasTurning Formulas

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Turning ParametersTurning Parameters

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Turning Feeds & SpeedsTurning Feeds & Speeds

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Feeds & Speeds for Tool MaterialsFeeds & Speeds for Tool Materials

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Cost ElementsCost Elements

EquipmentToolingSetup timeLoad/unload timeDirect laborIndirect laborCycle time, idle timeOverhead rate

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Safety FactorsSafety Factors

Rotating parts or toolsHot, sharp chipsEye and skin irritation from cutting fluids

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Example from BookExample from Book

A 6-in long, 0.5 in diameter 304 stainless-steel rod is being reduced in diameter to 0.48 in by turning on a lathe. The spindle rotates at N=400 rpm , and the tool is traveling at an axial speed of 8 in/min. Calculate, the cutting speed, material removal rate, cutting time, and power.