SIU IT 208 - Chapter 4 Mechanical Methods of Material Removal (3 pages)

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Chapter 4 Mechanical Methods of Material Removal



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Chapter 4 Mechanical Methods of Material Removal

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Pages:
3
School:
Southern Illinois University
Course:
It 208 - Fundamentals of Mfg Processes
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Chapter 4 Mechanical Methods of Material Removal CUTTING PROCESS Chip formation Lathe Components 1 Bed supports all other major components 2 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 to the 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 Specifications 1 Swing the maximum diameter of the piece that can be machined 2 Length center to center distance from spindle to tailstock bed length distance from spindle to the end of the bed 4 Considerations that determine how fast to run a lathe 1 Workpiece material 2 Tool diameter 3 Diameter of the work piece 4 Depth of cut Cutting fluids provide 3 major functions 1 Lubrication 2 Cooling 3 Chip removal Milling 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 Machines 1 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 Boring Drilling Stock is held stationary and the drill is rotated Boring Cutting tool is stationary and the material rotated Reaming and Honing Reamer 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 hole 2 Center drill the start of the hole 3 Use a small twist drill for a pilot hole 4 Twist drill a larger hole 5 Bore out the desired diameter 6 Ream the final diameter 7 Hone the final surface finish Sawing 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 Punching Shearing Process of slitting flat stock up to 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 considerable shock 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 Speeds Cutting 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 using a 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 RPM


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