Lathe Components Bed: 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.
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.
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.
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.
Lathe Accessories Carriage and Cross Slide Stops Devices for Turning Parts with Various Tapers Milling, Sawing, Gear-Cutting, and Grinding Attachments Various Attachments for Boring, Drilling, and Thread Cutting
What are Holes used For? Typical for assembly with fasteners i.e. screws, bolts, rivets Weight reduction Ventilation Access to inside parts Appearance
Drilling is a Common Process!!! THE COST OF HOLE MAKING IS AMONG THE HIGHEST MACHINING COSTS IN AUTOMOTIVE ENGINE PRODUCTION
Properties Burring on the bottom surface upon breakthrough requires further machining Diameters of holes are usually oversize Quality of drill Thermal properties Reaming and honing improve dimensional accuracy
Standard-Point Twist Drill Point angle (118-135deg) Lip-relief angle (7-15deg) Chisel-edge angle (125-135deg) Helix angle (15-30deg) Diameter range from 0.5-150mm
Other Types of Drills Step Drill Produces 2 or more different diameters Core Drill Makes an existing hole larger Counterboring & Countersinking Produce depressions on the surface to accommodate the heads of screws/bolts
More Drill Types Center drill Produces small hole on the end of a workpiece Spot drill Starts a hole at the desired location Spade drill Removable bits, produces large-diameter or deep holes Higher stiffness (absence of flutes) Straight-flute drill Gun drill
Material-Removal Rate MRR=(pi*D^2)f*N / 4 Pi*D^2 / 4= cross sectional area F = the distance penetrated per revolution N = rotational speed
General Troubleshooting ProblemProbable causes Drill breakageDull bit, chips clogging flutes, feed to high, lip relief angle too small Excessive drill wearCutting speed to high, ineffective fluid, rake angle too high, drill burned when sharpened Tapered holeDrill misaligned or bent, lips not equal Oversize holeSame as above, machine spindle loose, chisel edge not central, side force on workpiece Poor hole surface finishDull bit, ineffective fluid, welding of workpiece on drill margin, improperly ground drill, improper alignment
Considerations Drilling should be perpendicular to the surface Interrupted holes should be avoided Hole bottoms should match standard drill point angles Through holes preferred to blind holes Preexisting holes or dimples help center the drill Blind holes must be drilled deeper than subsequent reaming or tapping operations
What is Reaming An operation used to make an existing hole dimensionally more accurate and/or to improve surface finish For further accuracy and surface finish, holes may be burnished, ground or honed.
Peripheral Milling Peripheral Milling is when the cutter is longer than the width of the cut. a.k.a.- Slab Milling The axis of the cutter is usually parallel to the work piece surface.
Face Milling the cutter is mounted on a spindle having an axis of rotation perpendicular to the workpiece surface. Leaves feed marks on the machined surface.
End Milling The 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.
Conventional Milling a.k.a- Up Milling The Direction of cutter rotation opposes the feed motion.
Climb Milling a.k.a.- Down Milling The direction of cutter rotation is the same as the feed motion.
Other Types of Milling Straddle Milling Form Milling Slotting and Slitting Uses circular cutters
Tool holders Arbor Cutters Mounted on an arbor Used in peripheral, face, straddle and form milling.
Shank-Type Milling Cutter and shank are one peice
Design 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.
Troubleshooting Tool BreakageTool material lacks toughness, improper angles. Excessive Tool Wearimproper tool material, improper tool fluids. Rough Surface FinishFeed per tooth too high, tool chipped or worn. Chatter MarksInsufficient stiffness of system, external vibrations. BreakoutLead angle too low, feed and depth of cut too high.
Milling Machines First Milling Machine Built in 1820 by Eli Whitney
Column-and-Knee type Most common milling machines.
Basic Components Work Table Saddle Knee Overarm Head
Bed Type Work table is mounted is mounted directly on the bed. Not versatile High Stiffness Used for high production work
Other Milling Machines Planer-Type Several heads and cutters able to mill different surfaces Rotary-Table One or more heads for face milling. Computer Numerical Control Able to mill, drill, bore and tap with repetitive accuracy Profile Milling Machines 5 axes of movement.
Planning and Shaping Planning 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 hp Shaping Tool does the moving Small less than 1m X 2m
introduction Broaching and Broaching machines Sawing Filing Gear Manufacturing by Machining
Broaching 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.
Broaching is just as effective as Boring Milling Shaping Reaming
Broaching machines are very expensive but these machines yield a very high quantity of production runs.
Uses a single pass for finished shapes or sized Produces close tolerances and good surface finish Uses a multipoint cutting tool (broach) Has the roughing and finishing teeth on the same tool
Sawing Sawing is an old common operation dating back to around 1000 B.C Sawing is an efficient bulk removal process and can produce near net shape materials The process wastes little material Most common use of saws Hacksaws Circular saws Band saws Friction sawing
Hacksaws Hacksaws were developed in the 1960’s. Good for cutting off bars, rods, and structural shapes
Power hacksaws Fast They work smoothly and efficiently even under heavy-duty operation. With normal care these machines are indestructible.
Circular sawing Circular 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 periphery Rotating blade is fed into a stationary workpiece Produces a narrow cut and a good surface finish
Circular saws also called cold saws when cutting metal They are used for high production rate sawing Cold sawing is used in industry very commonly particularly for cutting large crossed sections. Diamond Saw Blades For Marble And Limestone saw blade for plastics