logging in or signing up Basic Machine Shop Safety and Operation ahabal Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 2402 Category: Education License: Some Rights Reserved Like it (5) Dislike it (0) Added: February 26, 2010 This Presentation is Public Favorites: 1 Presentation Description No description available. Comments Posting comment... By: anzajulius (7 month(s) ago) i like this and wish u can send it to me. Saving..... Post Reply Close Saving..... Edit Comment Close By: jaro5452 (9 month(s) ago) please i need to download this.very informative. Saving..... Post Reply Close Saving..... Edit Comment Close By: boyoman (10 month(s) ago) its a good presentation..i learn a loy of good things.. Saving..... Post Reply Close Saving..... Edit Comment Close By: vsdhote (11 month(s) ago) kindly send me presentation as soon as possible. its veeeeeeeeeeery nice Saving..... Post Reply Close Saving..... Edit Comment Close By: haseebkhan2 (12 month(s) ago) Nicely presented almost all the expect were covered .Will highly appreceate if you let me download this video. Thanks Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript BASIC MACHINE SHOP SAFETY and OPERATION : by: Anthony Habal 1 BASIC MACHINE SHOP SAFETY and OPERATION INTRODUCTION : 2 2/26/2010 INTRODUCTION The progress of humanity throughout the ages has been governed by the type of tools available. Ever since primitive people used rocks as hammers or weapons to kill animals for food, tools have governed our standard of living. The use of fire to extract metals from ore led to the development of newer or better tools. The harnessing of water led to the development of hydropower, which greatly improved humanity’s well-being. The high standard of living we enjoy today did not just happen. It has been the result of the development of highly efficient machine tools over the past several decades. Processed foods, automobiles, telephones, televisions, refrigerators, clothing, books, and practically everything else we use are produced by machinery. TURNING : 3 2/26/2010 TURNING Turning is one of the basic machining processes. Turning produces solids of revolutions which can be tightly tolerance because of the specialized nature of the operation. Turning is performed on a machine called a lathe in which the tool is stationary and the part is rotated. TYPES OF LATHE MACHINE : 4 2/26/2010 TYPES OF LATHE MACHINE Engine Lathe Slide 5: 5 2/26/2010 Engine Lathe CNC Lathe TYPES OF LATHE MACHINE Slide 6: 6 2/26/2010 Additional Lathes Then and now Vertical CNC Lathe MAIN PARTS OF LATHE MACHINE : 7 2/26/2010 MAIN PARTS OF LATHE MACHINE Tailstock Headstock Bed Carriage CUTTING TOOLSProperties of a Good Cutting Tools : 8 2/26/2010 CUTTING TOOLSProperties of a Good Cutting Tools 1. Hard 2. Tough 3. Heat resistant 4. Wear resistant Cutting Tool Materials : 9 2/26/2010 Cutting Tool Materials High Speed Steel (HSS) Carbide Cemented Carbide Ultrafine Particle Carbide Coated Carbide Cermet Ceramics Polycrystalline Compacts Cubic boron nitride (CBN) Diamond Cutting Tool Angle : 10 2/26/2010 Cutting Tool Angle - clearance angle - wedge angle - rake angle a - primary cutting edge b - secondary cutting edge c - clearance face of the primary cutting edge d - top face e - clearance face of the secondary cutting edge Reference Values for Cutting Tool Angles High-Speed Steel Material to be cut Cemented carbide : 11 2/26/2010 Reference Values for Cutting Tool Angles High-Speed Steel Material to be cut Cemented carbide Turning Processes : 12 2/26/2010 Turning Processes 1. Longitudinal or straight turning 2. Transversal turning or facing Slide 13: 13 2/26/2010 3. Angular turning or taper turning 4. Profile turning Slide 14: 14 2/26/2010 5. Thread cutting Rules for Longitudinal Turning and Facing : 15 2/26/2010 Rules for Longitudinal Turning and Facing 1. The workpiece should be chucked tightly and safely. 2. A large plan angle should be used for Workpiece that are likely to bend. 3. Revolutions and feed must be determined correctly. 4. The workpiece should be turned a short end and the diameter measured when the machine is disengaged. 5. For setting the cutting depth, the adjusting dials on the cross slide and compound slide should be used. 6. Before disengaging the machine, the turning tool should be withdrawn from the Workpiece otherwise the cutting edge can break. 7. At the end of the turning length, the feed must be disengaged in time. 8. For finishing, a properly ground finishing tool must be used. Smooth filing of the Workpiece should be avoided as the cylindrical shape may be spoiled. 9. For facing, the tool must be set exactly on the center and must be moved outwards. Methods of Setting or Mounting of Workpiece : 16 2/26/2010 Methods of Setting or Mounting of Workpiece 1. Clamp on the 3-jaw or 4-jaw chuck 2. Chuck to center 3. Chuck to steady rest 4. Between centers 5. Clamp on the face plate Slide 17: 17 2/26/2010 Cutting Speed, Feed and Depth of Cut To operate a lathe efficiently, the machinist must consider the importance of cutting speeds, feeds and depth of cuts. Much may be lost if the lathe is not set at the proper spindle speed and if the proper feed rate is not selected. Slide 18: 18 2/26/2010 Feeds and Speeds, Lathes The recommended surface cutting speed (S); or the speed at which the material passes the cutting edge of the tool; for any particular material can generally be found in most good machining handbooks. Typical examples are: Aluminum - 45 meters per min (m/min) Mild Steel -28m/min To calculate the lathe spindle speed (N) required to achieve the recommended cutting speed use the following formula. N = 1000 x S (m/min) pi x D (mm) Where D = diameter of Workpiece and 1000 is the correction factor required -cutting speed is meters/min, diameter in mm. Slide 19: 19 2/26/2010 Feeds and Speeds, Lathes The diameter of the finished size is usually used in this formula for all practical purposes although blank diameter or the mean of blank and finished diameter may also be used. Example: Calculate spindle speed required to turn a 30mm diameter in mild steel at the recommended cutting speed of 28 m/min. D=30 S=28 N = 1000x28 3.14 x 30 = 28000 94.25 N = 297 R.P.M Slide 20: 20 2/26/2010 Cutting Speed (CS) May be defined as the rate at which a point on the work circumference travels past the cutting tool. Cutting speed is always expressed in feet per minute (ft/min) or in meters per minute (m/min). To determine the RPM, divide CS by the circumference of the Workpiece. Lathe Cutting Speed in Meters per Minute Using a High Speed Steel Tool bit : 21 2/26/2010 Lathe Cutting Speed in Meters per Minute Using a High Speed Steel Tool bit Slide 22: 22 2/26/2010 Feed May be defined as the distance the cutting tool advances along the length of the work for every revolution of the spindle. The feed of an engine lathe is dependent on the speed of the lead screw or feed rod. Feeds for Various Materials Using a High Speed Steel Cutting Tool : 23 2/26/2010 Feeds for Various Materials Using a High Speed Steel Cutting Tool Slide 24: 24 2/26/2010 Depth of Cut May be defined as the depth of the chip taken by the cutting tool and is one-half the total amount removed from the Workpiece in one cut. When machining a Workpiece, take only one roughing and one finishing cut if possible. Slide 25: 25 2/26/2010 MILLING Milling is as fundamental as drilling among powered metal cutting processes. Milling is versatile for a basic machining process, but because the milling set up has so many degrees of freedom, milling is usually less accurate than turning or grinding unless especially rigid fixturing is implemented. Milling Machine : 26 2/26/2010 Milling Machine Milling Machine : 27 2/26/2010 Milling Machine Twin Vertical Boring Mill / Lathe Large vertical Machining Center Parts of Milling Machine : 28 2/26/2010 Parts of Milling Machine Horizontal Spindle Vertical Spindle Table Column Bed Z-axis Handwheel X-axis Handwheel Y-axis Handwheel Milling Cutters : 29 2/26/2010 Milling Cutters Plain milling cutter End mill Face milling cutter Side milling cutter Angular cutter T-slot cutter Dovetail cutter Formed cutter Metal slitting saw Fly-cutter Milling Processes : 30 2/26/2010 Milling Processes Face milling – is the process of producing a flat surface at right angles to the cutter axis. Side milling – is often used to machine a vertical surface on the sides or the ends of a Workpiece. Straddle milling – involves the use of two side milling cutters to machine the opposite sides of a Workpiece parallel in one cut. Dovetail milling – is the process of producing guide ways or parallel or angular surfaces with the use of dovetail cutter. Slotting – is the process of producing keyway, groove and slot with the use of end mills. Rules for Milling : 31 2/26/2010 Rules for Milling 1. The proper machine has to be selected. 2. Proper milling tools have to be selected. 3. The milling cutter must run true. 4. No blunt cutters should be used. 5. The Workpiece has to be clamped tightly and safely. 6. The correct revolutions and feed have to be selected. 7. Before setting the feed, check whether the Workpiece or milling table do not touch anywhere. 8. Coolant has to be given in time. Feeding Methods : 32 2/26/2010 Feeding Methods Conventional Milling Climb Milling Cutting Parameter : 33 2/26/2010 Cutting Parameter Cutting Speed (CS) Cutting speed of the cutter means the travel of one cutting tooth in meter per minute. The cutter must revolve at a specific number of RPM, depending on its diameter, to achieve the proper cutting speed. To determine the RPM, divide CS by the cutter circumference. Slide 34: 34 2/26/2010 Factors to consider in determining the proper RPM 1. The type of work material 2. The cutter material 3. The diameter of the cutter 4. The surface finish required 5. The depth of cut taken 6. The rigidity of the machine and work set-up Slide 35: 35 2/26/2010 Feeds and Speeds, Mills The calculation of spindle speed in milling uses the same formula as that for turning to convert from linear cutting speed. N = 1000 x S (m/min) pi x D (mm) Where D = diameter of milling cutter in mm. Where a lathe has a single tool and feed can simply be expressed as feed per revolution; milling cutters generally have more than one cutting edge –introducing the concept of tooth loading, or table feed per tooth. Generally table feed can be provided in one of two ways (either, in the case of C.N.C. milling). Either by a separate motor –in this case table speed is expressed in mm/min; or by the spindle motor, expressed in mm/spindle rev. Slide 36: 36 2/26/2010 Feeds and Speeds, Mills In the first instance: Table feed (mm/min)=Feed (mm/tooth) x No. of teeth x N (rev/min) In the second instance: Table feed (mm/rev) = Feed (mm/tooth) x No. of teeth Example 1: A 100mm diameter shell mill with 16 teeth is to be used to machine Aluminum at a cutting speed of 45 m/min. The recommended tooth loading for this particular cutter is 0.1 mm/tooth. Find the table feed in mm/min. First calculate the spindle speed. N = 1000 x 45 = 143rev/min pi x 100 Next calculate the table feed (mm/min) Table feed (mm/min) = feed/tooth (mm) x No. of teeth x N (rev/min) = 0.1 x 16 x 143 = 228 mm/min Slide 37: 37 2/26/2010 Feeds and Speeds, Mills Example 2: A 16mm diameter end mill with 6 teeth is to machine mild steel at a cutting speed of 28m/min. The recommended tooth loading for this tool is 0.05mm/tooth. Find table feed in mm/rev. This is a simpler calculation: Table feed (mm/rev) = feed (mm/tooth) x No. of teeth. = 0.05 x 6 = 0.3 mm/rev. Tooth loading will remain the same regardless of whether the correct cutting speed is used or not. Milling Machine Cutting Speeds : 38 2/26/2010 Milling Machine Cutting Speeds Factors to consider in determining the feed : 39 2/26/2010 Factors to consider in determining the feed 1. The depth and width of cut. 2. The design or type of cutter. 3. The sharpness of the cutter. 4. The Workpiece material. 5. The strength and uniformity of the Workpiece. 6. The type of finish and accuracy required. 7. The power and rigidity of the machine, the holding device and the tooling set-up. Recommended Feed per Tooth for High Speed Steel Cutters (mm/tooth) : 40 2/26/2010 Recommended Feed per Tooth for High Speed Steel Cutters (mm/tooth) Slide 41: 41 2/26/2010 Recommended Feed per Tooth for High Speed Steel Cutters (mm/tooth) Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) : 42 2/26/2010 Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) : 43 2/26/2010 Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) Depth of Cut : 44 2/26/2010 Depth of Cut Roughing cuts should be deep, with a feed as heavy as the work and machine will permit. Finishing cuts should be light, with a finer feed than is used for roughing cuts. Methods in Setting-up a Workpiece : 45 2/26/2010 Methods in Setting-up a Workpiece 1. Using a machine vise 2. Using a strap clamp 3. Using a toe clamp 4. Using a rotary table 5. Using an indexing head Slide 46: 46 2/26/2010 GRINDING Surface grinding is the process or operation of passing a Workpiece fixed to a table moving longitudinally and transversely under a fixed location high speed, rotating grinding (generally stone) wheel. Diamond wheels may be used for harder materials. Cylindrical grinding is the process of moving a rotating piece (as in a lathe) against a opposite rotating stone grinding wheel. The grinding wheel can be moved either across the outer or the inner diameter of a cylindrical work piece. Newer CNC grinders can finish grind tapers, contours and steps in a single operation. The grinder in our shop is similar those on the next page. Precision 0.0001” or 0.0025 mm (average human hair = .003”) Types of Grinding Machine : 47 2/26/2010 Types of Grinding Machine Surface Grinder Cylindrical Grinder Slide 48: 48 2/26/2010 Jig Grinder Tool & Cutter Grinder Optical Profile Grinder Parts of a Grinding Machine : 49 2/26/2010 Base Table Column Wheel head Table Traverse Hand wheel Cross feed Hand wheel Machine control Parts of a Grinding Machine ABRASIVES FOR GRINDING : 50 2/26/2010 ABRASIVES FOR GRINDING Two Classes of Abrasives 1. Natural Abrasives Example – Sandstone, Garnet, Emery, Flint, Quartz and Corundum 2. Manufactured Abrasives Example – Aluminum Oxide and Silicon Carbide Slide 51: 51 2/26/2010 Types of Manufactured Abrasives Aluminum Oxide – is generally used for high tensile strength materials, including all ferrous metals except cast iron. 2. Silicon Carbide – is suited for materials that have a low tensile strength and high density, such as cemented carbides, stone and ceramics. It is also used for cast iron and most nonferrous and non-metal materials. Slide 52: 52 2/26/2010 Grinding Wheel Grain Size Factors affecting the selection of grain size. 1. The type of surface finish desired. 2. The type of material being ground. 3. The amount of material to be removed. 4. The area of contact between the wheel and the Workpiece. Bond : 53 2/26/2010 Bond Bond Types Vitrified Bond Resinoid Bond Rubber Bond Shellac Bond Metal Bond Grade : 54 2/26/2010 Grade Factors to consider in the selection of grade of wheel to be used Hardness of the material Area of contact Condition of the machine The speed of the grinding wheel and the Workpiece Rate of feed Operator characteristics StructureThe structure of a grinding wheel is the space relationship of the grain and bonding material to the voids that separate them. : 55 2/26/2010 StructureThe structure of a grinding wheel is the space relationship of the grain and bonding material to the voids that separate them. Factors affecting the selection of wheel structure The type of material being ground. Area of con tact. Finish required. Method of cooling. Straight Grinding Wheel Marking System : 56 2/26/2010 Straight Grinding Wheel Marking System Abrasive Type Grain Size Grade Structure Bond Type A 46 M 5 V A - Aluminum Oxide C - Silicon Carbide Slide 57: 57 2/26/2010 Common Grinding Wheel Shapes and Applications Slide 58: 58 2/26/2010 Slide 59: 59 2/26/2010 Basic Functions of Grinding Wheels Generation of cylindrical, flat and curved surfaces 2. Removal of stock 3. Production of highly finished surfaces 4. Cutting-off operations 5. Production of sharp edges and points Slide 60: 60 2/26/2010 Truing and Dressing of Grinding Wheel Truing – is the process of making a grinding wheel round and concentric with its spindle axis and producing the required form or shape on the wheel. Dressing – is the operation of removing the dull grains and metal particles. Slide 61: 61 2/26/2010 Types of Grinding Wheel Dresser 1. Steel star dresser 2. Diamond dresser 3. Roller dresser Slide 62: 62 2/26/2010 Types of Grinding Fluids Soluble oil and water 2. Soluble chemical grinding fluids and water 3. Straight oil grinding fluids Slide 63: 63 2/26/2010 Functions of Grinding Fluids Reduction of grinding heat 2. Lubrication of the surface between the workpiece and the grinding wheel 3. Removal of metal chips 4. Control of grinding dust Slide 64: 64 2/26/2010 Rules in Grinding Use a silicon carbide wheel for low tensile strength material and an aluminum oxide wheel for high tensile strength materials. 2. Use a hard wheel on soft materials and a soft wheel on hard materials. 3. If the wheel is too hard, increase the speed of the work or decrease the speed of the wheel to make it act as a softer wheel. Slide 65: 65 2/26/2010 4. If the wheel appears too soft or wears rapidly, decrease the speed of the work or increase the speed of the wheel, but not above its recommended speed. 5. A glazed wheel will affect the finish, accuracy and metal removal rate. 6. If a wheel wears too quickly, the cause may be: the wheel is too soft, wheel speed is too low, work speed is too fast, feed rate is too great, face of the wheel is too narrow and the surface of the work is interrupted by holes or grooves. Rules in Grinding Slide 66: 66 2/26/2010 Thank you You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
Basic Machine Shop Safety and Operation ahabal Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 2402 Category: Education License: Some Rights Reserved Like it (5) Dislike it (0) Added: February 26, 2010 This Presentation is Public Favorites: 1 Presentation Description No description available. Comments Posting comment... By: anzajulius (7 month(s) ago) i like this and wish u can send it to me. Saving..... Post Reply Close Saving..... Edit Comment Close By: jaro5452 (9 month(s) ago) please i need to download this.very informative. Saving..... Post Reply Close Saving..... Edit Comment Close By: boyoman (10 month(s) ago) its a good presentation..i learn a loy of good things.. Saving..... Post Reply Close Saving..... Edit Comment Close By: vsdhote (11 month(s) ago) kindly send me presentation as soon as possible. its veeeeeeeeeeery nice Saving..... Post Reply Close Saving..... Edit Comment Close By: haseebkhan2 (12 month(s) ago) Nicely presented almost all the expect were covered .Will highly appreceate if you let me download this video. Thanks Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript BASIC MACHINE SHOP SAFETY and OPERATION : by: Anthony Habal 1 BASIC MACHINE SHOP SAFETY and OPERATION INTRODUCTION : 2 2/26/2010 INTRODUCTION The progress of humanity throughout the ages has been governed by the type of tools available. Ever since primitive people used rocks as hammers or weapons to kill animals for food, tools have governed our standard of living. The use of fire to extract metals from ore led to the development of newer or better tools. The harnessing of water led to the development of hydropower, which greatly improved humanity’s well-being. The high standard of living we enjoy today did not just happen. It has been the result of the development of highly efficient machine tools over the past several decades. Processed foods, automobiles, telephones, televisions, refrigerators, clothing, books, and practically everything else we use are produced by machinery. TURNING : 3 2/26/2010 TURNING Turning is one of the basic machining processes. Turning produces solids of revolutions which can be tightly tolerance because of the specialized nature of the operation. Turning is performed on a machine called a lathe in which the tool is stationary and the part is rotated. TYPES OF LATHE MACHINE : 4 2/26/2010 TYPES OF LATHE MACHINE Engine Lathe Slide 5: 5 2/26/2010 Engine Lathe CNC Lathe TYPES OF LATHE MACHINE Slide 6: 6 2/26/2010 Additional Lathes Then and now Vertical CNC Lathe MAIN PARTS OF LATHE MACHINE : 7 2/26/2010 MAIN PARTS OF LATHE MACHINE Tailstock Headstock Bed Carriage CUTTING TOOLSProperties of a Good Cutting Tools : 8 2/26/2010 CUTTING TOOLSProperties of a Good Cutting Tools 1. Hard 2. Tough 3. Heat resistant 4. Wear resistant Cutting Tool Materials : 9 2/26/2010 Cutting Tool Materials High Speed Steel (HSS) Carbide Cemented Carbide Ultrafine Particle Carbide Coated Carbide Cermet Ceramics Polycrystalline Compacts Cubic boron nitride (CBN) Diamond Cutting Tool Angle : 10 2/26/2010 Cutting Tool Angle - clearance angle - wedge angle - rake angle a - primary cutting edge b - secondary cutting edge c - clearance face of the primary cutting edge d - top face e - clearance face of the secondary cutting edge Reference Values for Cutting Tool Angles High-Speed Steel Material to be cut Cemented carbide : 11 2/26/2010 Reference Values for Cutting Tool Angles High-Speed Steel Material to be cut Cemented carbide Turning Processes : 12 2/26/2010 Turning Processes 1. Longitudinal or straight turning 2. Transversal turning or facing Slide 13: 13 2/26/2010 3. Angular turning or taper turning 4. Profile turning Slide 14: 14 2/26/2010 5. Thread cutting Rules for Longitudinal Turning and Facing : 15 2/26/2010 Rules for Longitudinal Turning and Facing 1. The workpiece should be chucked tightly and safely. 2. A large plan angle should be used for Workpiece that are likely to bend. 3. Revolutions and feed must be determined correctly. 4. The workpiece should be turned a short end and the diameter measured when the machine is disengaged. 5. For setting the cutting depth, the adjusting dials on the cross slide and compound slide should be used. 6. Before disengaging the machine, the turning tool should be withdrawn from the Workpiece otherwise the cutting edge can break. 7. At the end of the turning length, the feed must be disengaged in time. 8. For finishing, a properly ground finishing tool must be used. Smooth filing of the Workpiece should be avoided as the cylindrical shape may be spoiled. 9. For facing, the tool must be set exactly on the center and must be moved outwards. Methods of Setting or Mounting of Workpiece : 16 2/26/2010 Methods of Setting or Mounting of Workpiece 1. Clamp on the 3-jaw or 4-jaw chuck 2. Chuck to center 3. Chuck to steady rest 4. Between centers 5. Clamp on the face plate Slide 17: 17 2/26/2010 Cutting Speed, Feed and Depth of Cut To operate a lathe efficiently, the machinist must consider the importance of cutting speeds, feeds and depth of cuts. Much may be lost if the lathe is not set at the proper spindle speed and if the proper feed rate is not selected. Slide 18: 18 2/26/2010 Feeds and Speeds, Lathes The recommended surface cutting speed (S); or the speed at which the material passes the cutting edge of the tool; for any particular material can generally be found in most good machining handbooks. Typical examples are: Aluminum - 45 meters per min (m/min) Mild Steel -28m/min To calculate the lathe spindle speed (N) required to achieve the recommended cutting speed use the following formula. N = 1000 x S (m/min) pi x D (mm) Where D = diameter of Workpiece and 1000 is the correction factor required -cutting speed is meters/min, diameter in mm. Slide 19: 19 2/26/2010 Feeds and Speeds, Lathes The diameter of the finished size is usually used in this formula for all practical purposes although blank diameter or the mean of blank and finished diameter may also be used. Example: Calculate spindle speed required to turn a 30mm diameter in mild steel at the recommended cutting speed of 28 m/min. D=30 S=28 N = 1000x28 3.14 x 30 = 28000 94.25 N = 297 R.P.M Slide 20: 20 2/26/2010 Cutting Speed (CS) May be defined as the rate at which a point on the work circumference travels past the cutting tool. Cutting speed is always expressed in feet per minute (ft/min) or in meters per minute (m/min). To determine the RPM, divide CS by the circumference of the Workpiece. Lathe Cutting Speed in Meters per Minute Using a High Speed Steel Tool bit : 21 2/26/2010 Lathe Cutting Speed in Meters per Minute Using a High Speed Steel Tool bit Slide 22: 22 2/26/2010 Feed May be defined as the distance the cutting tool advances along the length of the work for every revolution of the spindle. The feed of an engine lathe is dependent on the speed of the lead screw or feed rod. Feeds for Various Materials Using a High Speed Steel Cutting Tool : 23 2/26/2010 Feeds for Various Materials Using a High Speed Steel Cutting Tool Slide 24: 24 2/26/2010 Depth of Cut May be defined as the depth of the chip taken by the cutting tool and is one-half the total amount removed from the Workpiece in one cut. When machining a Workpiece, take only one roughing and one finishing cut if possible. Slide 25: 25 2/26/2010 MILLING Milling is as fundamental as drilling among powered metal cutting processes. Milling is versatile for a basic machining process, but because the milling set up has so many degrees of freedom, milling is usually less accurate than turning or grinding unless especially rigid fixturing is implemented. Milling Machine : 26 2/26/2010 Milling Machine Milling Machine : 27 2/26/2010 Milling Machine Twin Vertical Boring Mill / Lathe Large vertical Machining Center Parts of Milling Machine : 28 2/26/2010 Parts of Milling Machine Horizontal Spindle Vertical Spindle Table Column Bed Z-axis Handwheel X-axis Handwheel Y-axis Handwheel Milling Cutters : 29 2/26/2010 Milling Cutters Plain milling cutter End mill Face milling cutter Side milling cutter Angular cutter T-slot cutter Dovetail cutter Formed cutter Metal slitting saw Fly-cutter Milling Processes : 30 2/26/2010 Milling Processes Face milling – is the process of producing a flat surface at right angles to the cutter axis. Side milling – is often used to machine a vertical surface on the sides or the ends of a Workpiece. Straddle milling – involves the use of two side milling cutters to machine the opposite sides of a Workpiece parallel in one cut. Dovetail milling – is the process of producing guide ways or parallel or angular surfaces with the use of dovetail cutter. Slotting – is the process of producing keyway, groove and slot with the use of end mills. Rules for Milling : 31 2/26/2010 Rules for Milling 1. The proper machine has to be selected. 2. Proper milling tools have to be selected. 3. The milling cutter must run true. 4. No blunt cutters should be used. 5. The Workpiece has to be clamped tightly and safely. 6. The correct revolutions and feed have to be selected. 7. Before setting the feed, check whether the Workpiece or milling table do not touch anywhere. 8. Coolant has to be given in time. Feeding Methods : 32 2/26/2010 Feeding Methods Conventional Milling Climb Milling Cutting Parameter : 33 2/26/2010 Cutting Parameter Cutting Speed (CS) Cutting speed of the cutter means the travel of one cutting tooth in meter per minute. The cutter must revolve at a specific number of RPM, depending on its diameter, to achieve the proper cutting speed. To determine the RPM, divide CS by the cutter circumference. Slide 34: 34 2/26/2010 Factors to consider in determining the proper RPM 1. The type of work material 2. The cutter material 3. The diameter of the cutter 4. The surface finish required 5. The depth of cut taken 6. The rigidity of the machine and work set-up Slide 35: 35 2/26/2010 Feeds and Speeds, Mills The calculation of spindle speed in milling uses the same formula as that for turning to convert from linear cutting speed. N = 1000 x S (m/min) pi x D (mm) Where D = diameter of milling cutter in mm. Where a lathe has a single tool and feed can simply be expressed as feed per revolution; milling cutters generally have more than one cutting edge –introducing the concept of tooth loading, or table feed per tooth. Generally table feed can be provided in one of two ways (either, in the case of C.N.C. milling). Either by a separate motor –in this case table speed is expressed in mm/min; or by the spindle motor, expressed in mm/spindle rev. Slide 36: 36 2/26/2010 Feeds and Speeds, Mills In the first instance: Table feed (mm/min)=Feed (mm/tooth) x No. of teeth x N (rev/min) In the second instance: Table feed (mm/rev) = Feed (mm/tooth) x No. of teeth Example 1: A 100mm diameter shell mill with 16 teeth is to be used to machine Aluminum at a cutting speed of 45 m/min. The recommended tooth loading for this particular cutter is 0.1 mm/tooth. Find the table feed in mm/min. First calculate the spindle speed. N = 1000 x 45 = 143rev/min pi x 100 Next calculate the table feed (mm/min) Table feed (mm/min) = feed/tooth (mm) x No. of teeth x N (rev/min) = 0.1 x 16 x 143 = 228 mm/min Slide 37: 37 2/26/2010 Feeds and Speeds, Mills Example 2: A 16mm diameter end mill with 6 teeth is to machine mild steel at a cutting speed of 28m/min. The recommended tooth loading for this tool is 0.05mm/tooth. Find table feed in mm/rev. This is a simpler calculation: Table feed (mm/rev) = feed (mm/tooth) x No. of teeth. = 0.05 x 6 = 0.3 mm/rev. Tooth loading will remain the same regardless of whether the correct cutting speed is used or not. Milling Machine Cutting Speeds : 38 2/26/2010 Milling Machine Cutting Speeds Factors to consider in determining the feed : 39 2/26/2010 Factors to consider in determining the feed 1. The depth and width of cut. 2. The design or type of cutter. 3. The sharpness of the cutter. 4. The Workpiece material. 5. The strength and uniformity of the Workpiece. 6. The type of finish and accuracy required. 7. The power and rigidity of the machine, the holding device and the tooling set-up. Recommended Feed per Tooth for High Speed Steel Cutters (mm/tooth) : 40 2/26/2010 Recommended Feed per Tooth for High Speed Steel Cutters (mm/tooth) Slide 41: 41 2/26/2010 Recommended Feed per Tooth for High Speed Steel Cutters (mm/tooth) Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) : 42 2/26/2010 Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) : 43 2/26/2010 Recommended Feed per Tooth for Cemented Carbide Cutters (mm/tooth) Depth of Cut : 44 2/26/2010 Depth of Cut Roughing cuts should be deep, with a feed as heavy as the work and machine will permit. Finishing cuts should be light, with a finer feed than is used for roughing cuts. Methods in Setting-up a Workpiece : 45 2/26/2010 Methods in Setting-up a Workpiece 1. Using a machine vise 2. Using a strap clamp 3. Using a toe clamp 4. Using a rotary table 5. Using an indexing head Slide 46: 46 2/26/2010 GRINDING Surface grinding is the process or operation of passing a Workpiece fixed to a table moving longitudinally and transversely under a fixed location high speed, rotating grinding (generally stone) wheel. Diamond wheels may be used for harder materials. Cylindrical grinding is the process of moving a rotating piece (as in a lathe) against a opposite rotating stone grinding wheel. The grinding wheel can be moved either across the outer or the inner diameter of a cylindrical work piece. Newer CNC grinders can finish grind tapers, contours and steps in a single operation. The grinder in our shop is similar those on the next page. Precision 0.0001” or 0.0025 mm (average human hair = .003”) Types of Grinding Machine : 47 2/26/2010 Types of Grinding Machine Surface Grinder Cylindrical Grinder Slide 48: 48 2/26/2010 Jig Grinder Tool & Cutter Grinder Optical Profile Grinder Parts of a Grinding Machine : 49 2/26/2010 Base Table Column Wheel head Table Traverse Hand wheel Cross feed Hand wheel Machine control Parts of a Grinding Machine ABRASIVES FOR GRINDING : 50 2/26/2010 ABRASIVES FOR GRINDING Two Classes of Abrasives 1. Natural Abrasives Example – Sandstone, Garnet, Emery, Flint, Quartz and Corundum 2. Manufactured Abrasives Example – Aluminum Oxide and Silicon Carbide Slide 51: 51 2/26/2010 Types of Manufactured Abrasives Aluminum Oxide – is generally used for high tensile strength materials, including all ferrous metals except cast iron. 2. Silicon Carbide – is suited for materials that have a low tensile strength and high density, such as cemented carbides, stone and ceramics. It is also used for cast iron and most nonferrous and non-metal materials. Slide 52: 52 2/26/2010 Grinding Wheel Grain Size Factors affecting the selection of grain size. 1. The type of surface finish desired. 2. The type of material being ground. 3. The amount of material to be removed. 4. The area of contact between the wheel and the Workpiece. Bond : 53 2/26/2010 Bond Bond Types Vitrified Bond Resinoid Bond Rubber Bond Shellac Bond Metal Bond Grade : 54 2/26/2010 Grade Factors to consider in the selection of grade of wheel to be used Hardness of the material Area of contact Condition of the machine The speed of the grinding wheel and the Workpiece Rate of feed Operator characteristics StructureThe structure of a grinding wheel is the space relationship of the grain and bonding material to the voids that separate them. : 55 2/26/2010 StructureThe structure of a grinding wheel is the space relationship of the grain and bonding material to the voids that separate them. Factors affecting the selection of wheel structure The type of material being ground. Area of con tact. Finish required. Method of cooling. Straight Grinding Wheel Marking System : 56 2/26/2010 Straight Grinding Wheel Marking System Abrasive Type Grain Size Grade Structure Bond Type A 46 M 5 V A - Aluminum Oxide C - Silicon Carbide Slide 57: 57 2/26/2010 Common Grinding Wheel Shapes and Applications Slide 58: 58 2/26/2010 Slide 59: 59 2/26/2010 Basic Functions of Grinding Wheels Generation of cylindrical, flat and curved surfaces 2. Removal of stock 3. Production of highly finished surfaces 4. Cutting-off operations 5. Production of sharp edges and points Slide 60: 60 2/26/2010 Truing and Dressing of Grinding Wheel Truing – is the process of making a grinding wheel round and concentric with its spindle axis and producing the required form or shape on the wheel. Dressing – is the operation of removing the dull grains and metal particles. Slide 61: 61 2/26/2010 Types of Grinding Wheel Dresser 1. Steel star dresser 2. Diamond dresser 3. Roller dresser Slide 62: 62 2/26/2010 Types of Grinding Fluids Soluble oil and water 2. Soluble chemical grinding fluids and water 3. Straight oil grinding fluids Slide 63: 63 2/26/2010 Functions of Grinding Fluids Reduction of grinding heat 2. Lubrication of the surface between the workpiece and the grinding wheel 3. Removal of metal chips 4. Control of grinding dust Slide 64: 64 2/26/2010 Rules in Grinding Use a silicon carbide wheel for low tensile strength material and an aluminum oxide wheel for high tensile strength materials. 2. Use a hard wheel on soft materials and a soft wheel on hard materials. 3. If the wheel is too hard, increase the speed of the work or decrease the speed of the wheel to make it act as a softer wheel. Slide 65: 65 2/26/2010 4. If the wheel appears too soft or wears rapidly, decrease the speed of the work or increase the speed of the wheel, but not above its recommended speed. 5. A glazed wheel will affect the finish, accuracy and metal removal rate. 6. If a wheel wears too quickly, the cause may be: the wheel is too soft, wheel speed is too low, work speed is too fast, feed rate is too great, face of the wheel is too narrow and the surface of the work is interrupted by holes or grooves. Rules in Grinding Slide 66: 66 2/26/2010 Thank you