9Lathe ComponentsBed: Usually made of cast iron. Provides a heavy rigid frame on which all the main components are mounted. • Ways: Inner and outer guide railsn that are precision machined parallel to assure accuracy of movement. • Headstock: mounted in a fixed position on the inner ways, usually at the left end. Using a chuck, it rotates the work. • Gearbox: inside the headstock, providing multiple speeds with a geometric ratio by moving levers.
10• Spindle: Hole through the headstock to which bar stock can be fed. • Chuck: 3-jaw (self centering) or 4-jaw (independent) to clamp part being machined.• Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock to fit the length of the work piece. An optional taper turning attachment would be mounted to it.• Tailstock Quill: Has a Morse taper to hold a lathe center, drill bit or other tool.• Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools.• Cross Slide: Mounted on the traverse slide of the carriage, and uses a handwheel to feed tools into the workpiece.
11• Tool Post: To mount tool holders in which the cutting bits are clamped. • Compound Rest: Mounted to the cross slide, it pivots around the tool post.• Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide.• Feed Rod: Has a keyway, with two reversing pinion gears, either of which can be meshed with the mating bevel gear to forward or reverse the carriage using a clutch.• Lead Screw: For cutting threads.• Split Nut: When closed around the lead screw, the carriage is driven along by direct drive without using a clutch.
12• Quick Change Gearbox: Controls the movement of the carriage using levers. • Steady Rest: Clamped to the lathe ways, it uses adjustable fingers to contact the workpiece and align it. Can be used in place of tailstock to support long or unstable parts being machined.• Follow Rest: Bolted to the lathe carriage, it uses adjustable fingers to bear against the workpiece opposite the cutting tool to prevent deflection.
13Lathe Accessories Carriage and Cross Slide Stops Devices for Turning Parts with Various TapersMilling, Sawing, Gear-Cutting, and Grinding AttachmentsVarious Attachments for Boring, Drilling, and Thread Cutting
34What are Holes used For? Typical for assembly with fasteners i.e. screws, bolts, rivetsWeight reductionVentilationAccess to inside partsAppearance
35Drilling is a Common Process!!! THE COST OF HOLE MAKING IS AMONG THE HIGHEST MACHINING COSTS IN AUTOMOTIVE ENGINE PRODUCTION
36PropertiesBurring on the bottom surface upon breakthrough requires further machiningDiameters of holes are usually oversizeQuality of drillThermal propertiesReaming and honing improve dimensional accuracy
37Standard-Point Twist Drill Point angle ( deg)Lip-relief angle (7-15deg)Chisel-edge angle ( deg)Helix angle (15-30deg)Diameter range from mm
39Other Types of Drills Step Drill Core Drill Produces 2 or more different diametersCore DrillMakes an existing hole largerCounterboring & CountersinkingProduce depressions on the surface to accommodate the heads of screws/bolts
41More Drill Types Center drill Spot drill Spade drill Produces small hole on the end of a workpieceSpot drillStarts a hole at the desired locationSpade drillRemovable bits, produces large-diameter or deep holesHigher stiffness (absence of flutes)Straight-flute drillGun drill
44Material-Removal Rate MRR=(pi*D^2)f*N / 4Pi*D^2 / 4= cross sectional areaF = the distance penetrated per revolutionN = rotational speed
45General Troubleshooting ProblemProbable causesDrill breakageDull bit, chips clogging flutes, feed to high, lip relief angle too smallExcessive drill wearCutting speed to high, ineffective fluid, rake angle too high, drill burned when sharpenedTapered holeDrill misaligned or bent, lips not equalOversize holeSame as above, machine spindle loose, chisel edge not central, side force on workpiecePoor hole surface finishDull bit, ineffective fluid, welding of workpiece on drill margin, improperly ground drill, improper alignment
47Considerations Drilling should be perpendicular to the surface Interrupted holes should be avoidedHole bottoms should match standard drill point anglesThrough holes preferred to blind holesPreexisting holes or dimples help center the drillBlind holes must be drilled deeper than subsequent reaming or tapping operations
48What is ReamingAn operation used to make an existing hole dimensionally more accurate and/or to improve surface finishFor further accuracy and surface finish, holes may be burnished, ground or honed.
494 Steps to AccuracyCenteringDrillingBoringReaming
56Peripheral MillingPeripheral Milling is when the cutter is longer than the width of the cut.a.k.a.- Slab MillingThe axis of the cutter is usually parallel to the work piece surface.
57Face Millingthe cutter is mounted on a spindle having an axis of rotation perpendicular to the workpiece surface.Leaves feed marks on the machined surface.
58End MillingThe cutter generally rotates on an axis vertical to the workpiece.It can be tilted to machine tapered surfaces. Cutting teeth are located on both the end face of the cutter and the periphery of the cutter body.Can produce a variety of surfaces at any depth.
59Conventional Milling a.k.a- Up Milling The Direction of cutter rotation opposes the feed motion.
60Climb Milling a.k.a.- Down Milling The direction of cutter rotation is the same as the feed motion.
61Other Types of Milling Straddle Milling Form Milling Slotting and SlittingUses circular cutters
62Tool holders Arbor Cutters Mounted on an arbor Used in peripheral, face, straddle and form milling.
63Shank-Type MillingCutter and shank are one peice
64Design and Operating Guidelines Basic cutters should be used as much as possible.Avoid expensive special cutters.Chamfers should be specified instead of radii.Chamfer-A furrow or groove, as in a column.Avoid internal cavities and pockets with sharp corners.Due to the difficulty of doing them.
65TroubleshootingTool Breakage Tool material lacks toughness, improper angles.Excessive Tool Wear improper tool material, improper tool fluids.Rough Surface Finish Feed per tooth too high, tool chipped or worn.Chatter Marks Insufficient stiffness of system, external vibrations.Breakout Lead angle too low, feed and depth of cut too high.
66Milling MachinesFirst Milling MachineBuilt in 1820 by Eli Whitney
67Column-and-Knee typeMost common milling machines.
69Bed Type Work table is mounted is mounted directly on the bed. Not versatileHigh StiffnessUsed for high production work
70Other Milling Machines Planer-TypeSeveral heads and cutters able to mill different surfacesRotary-TableOne or more heads for face milling.Computer Numerical ControlAble to mill, drill, bore and tap with repetitive accuracyProfile Milling Machines5 axes of movement.
71Planning and Shaping Planning Shaping Large workpieces 25m X 15m Work piece is mounted on a table and travels back and forth along a straight path.Cutting speeds can get up to 120 m/min with 150 hpShapingTool does the movingSmall less than 1m X 2m
73introduction Broaching and Broaching machines Sawing Filing Gear Manufacturing by Machining
74Broaching and Broaching machines Broaching is a similar technique to shaping with a long multiple-tooth cutter and is used to machine internal an external surfaces.
75Broaching is just as effective as BoringMillingShapingReaming
76Broaching machines are very expensive but these machines yield a very high quantity of production runs.
77Uses a single pass for finished shapes or sized Produces close tolerances and good surface finishUses a multipoint cutting tool (broach)Has the roughing and finishing teeth on the same tool
78SawingSawing is an old common operation dating back to around 1000 B.CSawing is an efficient bulk removal process and can produce near net shape materialsThe process wastes little materialMost common use of sawsHacksawsCircular sawsBand sawsFriction sawing
80Hacksaws Hacksaws were developed in the 1960’s. Good for cutting off bars, rods, and structural shapes
81Power hacksawsFastThey work smoothly and efficiently even under heavy-duty operation. With normal care these machines are indestructible.
82Circular sawingCircular sawing is a multipoint cutting process in which a circular tool is advanced against a stationary workpiece to sever parts or produce narrow slots.Uses thin circular blades with teeth on peripheryRotating blade is fed into a stationary workpieceProduces a narrow cut and a good surface finish
84Diamond Saw Blades For Marble And Limestone Circular saws also called cold saws when cutting metalThey are used for high production rate sawingCold sawing is used in industry very commonly particularly for cutting large crossed sections.Diamond Saw Blades For Marble And Limestonesaw blade for plastics