Lathe ComponentsShearing and PunchingChapter 4 Mechanical Methods of Material RemovalCUTTING PROCESSChip formation:Lathe Components1) Bed- supports all other major components2) Carriage- slides along the ways and consists of an assembly cross-slide, tool post, and apron.3) Headstock- fixed to the bed and has motors, pulleys, and v-belts that supply power tothe spindle (hollow) (work holding device attached to the spindle) 4) Tailstock- can slide along the ways and can be clamped down. Supports the part on the rear end.5) Feed rod and lead screw- used to provide power to the carriage to feed it along or across the work piece. Lathe Specifications1) Swing- the maximum diameter of the piece that can be machined2) Length- (center to center)- distance from spindle to tailstock (bed length)- distance from spindle to the end of the bed4 Considerations that determine how fast to run a lathe:1. Workpiece material2. Tool diameter3. Diameter of the work piece4. Depth of cut.Cutting fluids- provide 3 major functions1. Lubrication2. Cooling3. Chip removalMilling- A process that is capable of producing a variety of configurations using a multitooth tool, turns the tool and holds the workpiece to provide the cutting action Types of Milling Machines1) Horizontal- the spindle is placed horizontal (used for heavier cutting) 2) Vertical- the spindle is placed vertical (the most common type of milling machine) Planning - Cutting blades rotate while the material is passed through them.Routing - Uses specially shaped cutting tool to remove material in a defined geometry.Broaching - Specific file geometry is used to duplicate the profile of the broach inside a hole.Drilling and BoringDrilling - Stock is held stationary and the drill is rotated Boring - Cutting tool is stationary and the material rotatedReaming and HoningReamer- Similar to a drill, but has straight cutting edges and is used for finishing a hole to very close tolerances.Hones - Small grindstone used to “move” material and smooth out the final surface.Sequence for producing a large precision hole:1. Center punch location of hole2. Center drill the start of the hole3. Use a small twist drill for a pilot hole.4. Twist drill a larger hole5. Bore out the desired diameter6. Ream the final diameter7. Hone the final surface finishSawing Advantages: Quick and cheap method of material removal Disadvantages: Leaves rough surface on both sides of the cut.Saw “Set” – Making the kerf wider than the blade backing so that the blade will not bind in the kerf.Blade selection: Harder the material, the finer and closer the teeth. Steel 14-30 t.p.i., Aluminum 8-12 t.p.i.Circular Saws, Jig Saws, Hack Saws, Band, Saws, Chain Saws.Abrasive Saws- used to cut (grind) extremely hard materials cannot be used to cut soft materials because it will “load” the blade.Shearing and PunchingShearing- Process of slitting flat stock up to ½” in thickness Punching- Shearing any shaped hole in flat stock.Grinding – Removal of material by abrasion. “Dressing” a wheel is a process of using a diamond to remove the outer layer of a wheel,so that it becomes round (true) and the ends square.Grit Size – refers to the size of grit that will pass through the number of openings per linear inch in a sieve. (i.e. 100 grit sand paper)Cutting Tool Shapes (see fig. 4-50)Side, back, and end rake angles are determined by the materials being cut and the type of cut being made. Hard materials require very little side or back rake angle.High Speed Steel (HSS) – best choice for roughing purposes. They are inexpensive, can be easily resharpened, and are not extremely brittle. The HSS tools will take considerableshock. Their drawback is that they dull faster, especially in the cutting of harder metals. Carbide – Carbide tips will cut harder steels, but they are brittle and should not be used for roughing purposes. Carbide-tipped tools can produce closer tolerances and better finishes than the HSS tools. Ceramic tools - are not affected by heat, and can be operated at extremely high revolutions per minute. However, these tools are similar to glass in brittleness. Ceramic tools are generally used only for the final, very light cut on very hard steels. Feeds & SpeedsCutting Speed – is the velocity of the surface of a workpiece as it passes the cutting tool.Speed (SFPM) – given in surface feet per minute (SFPM). Spindle Speed – is the rotational speed in revolutions per minute at which the lathe, milling machine, saw, grinder, or drill press is running. Feed - the rate of advance of the cutting tool per revolution. Depth of Cut – is the distance to which the cutting tool enters the workpiece. PROBLEM SET 4-1 1. A 4-in.-diameter piece of mild, low-carbon steel is to be turned on a lathe using a carbide cutting tool. What is the optimum speed of the lathe? (Hint: Use Table 4-2.) From table 2, Cs = 550 sfpm, N = 525 RPM 2. A 0.5-in.-diameter hole is to be drilled in a piece of 316 stainless steel with a HSS drill.At what rpm should the drill press be set? From table 2, Cs= 100 sfpm, N = 764 RPM 3. A lathe has a maximum speed of 1500 rpm. Could it be run at this maximum rpm usinga carbide-tipped tool to cut a 2-in.-diameter piece of aluminum? Yes, From table 4-2, Cs = 1200 sfpm, Maximum recommended speed is 1528