NAIT Machinist Program - Lathes 150102e PDF

MACHINIST PROGRAM - FIRST PERIOD LATHES 150102e  OBJECTIVES 1. DESCRIBE SAFETY PRECAUTIONS WHEN USING A LATHE 2. DESCRIBE THE TYPES, SIZE AND RATED CAPACITY OF LATHES 3. DESCRIBE THE MAJOR PARTS OF A LATHE AND THEIR FUNCTION 4. DESCRIBE WORKHOLDING DEVICES USED ON A LATHE 5. DESCR...

MACHINIST PROGRAM - FIRST PERIOD LATHES 150102e  OBJECTIVES 1. DESCRIBE SAFETY PRECAUTIONS WHEN USING A LATHE 2. DESCRIBE THE TYPES, SIZE AND RATED CAPACITY OF LATHES 3. DESCRIBE THE MAJOR PARTS OF A LATHE AND THEIR FUNCTION 4. DESCRIBE WORKHOLDING DEVICES USED ON A LATHE 5. DESCRIBE TOOL POSTS AND CUTTING TOOL HOLDERS OBJECTIVE 1 SAFETY PRECAUTIONS SAFETY WHAT ARE SOME GOOD SAFETY PRINCIPLES TO FOLLOW WHEN USING A LATHE? Wear appropriate CSA-certified safety glasses. Make sure entanglement hazards are removed (e.g. loose clothing, jewellery, etc.). Tie back and confine long hair. Keep the floor free from obstructions, or slip hazards. Make sure the lathe has a start/stop button within easy reach of the operator. LATHES SAFETY Centre-drill work deeply enough to provide support for the piece while it is turning. Secure and clamp the piece being worked. Use a lifting device to handle heavy chucks or work. Refer to Materials Handling for additional information. Inspect chucks for wear or damage. Flying pieces can be very dangerous. REMOVE CHUCK WRENCH IMMEDIATELY AFTER ADJUSTING CHUCK. Remove all tools, measuring instruments and other objects from saddle or lathe bed before starting machine. LATHES SAFETY Keep all lathe cutting tools sharp. Ensure that the chip and coolant shields are in place. Shut off the power supply to the motor before mounting or removing accessories. Stop lathe before taking measurements of any kind. Use a vacuum, brush or rake to remove cuttings only after the lathe has stopped moving. Keep working surface clean of scrap, tools and materials. Keep floor around lathe clean and free of oil and grease. LATHES SAFETY APPROPRIATE CHIP CONTROL IS A SAFETY REQUIREMENT. LATHES OBJECTIVE 2 IDENTIFICATION: TYPES SIZES RATED CAPACITY LATHES  SIZING THREE MAIN METHODS OF SIZING A LATHE: THE SWING….THE GREATEST DIAMETER WORKPIECE THAT CAN BE TURNED WITHOUT HITTING THE WAYS. DISTANCE BETWEEN CENTERS…. THE LONGEST WORK THAT COULD BE SUPPORTED BETWEEN CENTERS ON A LATHE. LENGTH OF BED…..BASICALLY THE DISTANCE FROM ONE END OF THE LATHE TO THE OTHER. LATHES  COMMON SIZING Swing (Diameter) Length Between Size Power over Bed Centres in mm in mm Hp kW 1 + + Small 10 250 30 750 /4 0.2 Medium 20 500 60 to 72 1500 to 1800 5 to 15 3.7 to 11.2 Large 48 1200 240 6000 20 to 60 15 to 45 LATHES TYPES – ENGINE LATHE LATHES TYPES – TURRET LATHE LATHES TYPES – AUTOMATIC LATHE (AUTOMATIC SCREW MACHINE) LATHES TYPES – TRACER LATHE TRACER LATHE - VIDEO LATHES TYPES – CNC LATHE PRODUCTION WORK MORE AND MORE COMMON CHEAPER AND EASIER TO PROGRAM USED FOR ONE OFFS AS WELL REQUIRES MORE SKILL (PROGRAMMING AND SETUP) TURNING AND THREADING ON A CNC - VIDEO LATHES  OBJECTIVE 3 DESCRIBE THE MAJOR PARTS OF A LATHE AND THEIR FUNCTION The Lathe Bed Rack Gear Figure 7 - Bed of a lathe. Flat side allows for thermal Expansion Figure 8 - Inverted prism ways. The Headstock Figure 9 - Headstock. Headstock Gears  Headstock The headstock of the lathe is attached to the left side of the bed and houses the spindle, bearings, gears and belts that drive the spindle. Levers that control speed and feed selections are located on the headstock. The working end of the spindle is called the spindle nose. Spindle are manufactured with a Morse Taper in the bore to permit the mounting of 60 degree Centers Lathe Components SPINDLE NOSE TYPES  Types of spindle noses Threaded spindle noses Taper and Key (type L) Camlock (Type D1) Figure 10 - Threaded spindle nose. Figure 11 - Taper and key spindle nose. D – Style Camlock Spindle Nose Figure 12 - Cam lock spindle nose. Lathe Components Head Stock End or Back Gear Set Figure 13 - Back gears. Lathe Components The End Gear is a component of the Quick Change Gearbox Lathe Components QUICK CHANGE GEARBOX AND FEED REVERSE LEVER Feed Reverse Lever( Used to reverse the rotation of the feed rod and lead screw Quick Change Gearbox  Quick Change gear box The quick-change gear box allows quick and easy changing of the feed rates. It allows for the selections of inch and metric threads. The gears in the quick change gear box provide power to the lead screw and the feed rod. The Quick-change gearbox is timed to the spindle rotation for accurate Feeds and screw thread pitches Lathe Parts Lead Screw and Feed Rod Lead Screw, Feed Rod and Rack The Lead Screw transmits power to the carriage for threading. (Often made with 4 TPI, Metric Lathes would be 6 mm pitch) The Feed Rod transmits power to the carriage for longitudinal and cross feeding operations such as turning, facing and boring. Feed System Protection : Shear pins and slip clutches prevent damage from sudden shock or overload. Thread Chasing Dial Figure 15 - Lead screw, feed rod and rack. Half-Nut Engagement Chart Lathe Components Lathe Carriage Parts Figure 16 - Carriage. Carriage Lock Carriage lock Used to face work pieces in an effort to eliminate convex or concave Faces. Locking the carriage is very important when facing large diameter work pieces. Figure 16 - Carriage.  Carriage Made up of three main parts of the Carriage include: Saddle… H shaped casting mounted directly on the ways and moving longitudinal or parallel to the axis of the spindle. Cross-slide…sits on top of the saddle and moves at right angles to the axis of the spindle. Apron…hangs down in front of the saddle and houses the drive gears, levers, other devises that control the movements of the carriage. Note Lathes are available with Direct reading Dials and Indirect Reading Dials. Direct: All graduations on the dial are based upon the amount of material removal on the work piece. (.001 =.001 off the work piece. Indirect : The material removal relates to the graduated dial reading (.001 on the dial equals.002 off the diameter. ) Figure 17 - Cross-feed handwheel and graduated dial.  Compound Rest Note The Reading on the graduated dial on the compound is actual value (.001 =.001 movement or an Indirect dial when used for diameter reduction) Figure 18 - Compound rest.  Compound Rest The compound rest can rotate 360 degrees and is made to extend shoulders or for cutting short steep tapers. It is used for cutting external and internal tapers. It is quick and easy to set up and can be dialed in to cut a very accurate Short taper. Lathe Apron Assembly Often called the half nut lever. Used for threading Figure 19 - Apron.  Apron Controls on the Apron include: The split-nut lever…closes the split-nut on the lead screw when threading. Automatic feed lever…engages the power feed for the carriage and cross- slide. Feed change lever…selects whether the carriage or cross-slide moves under power when the automatic feed lever is engaged. Carriage hand wheel… connected to a pinion gear which is in turn connected to a rack. Provides longitudinal movement of the carriage Apron Controls Lathe Components Lathe Tailstock Figure 20 - Tailstock.  Tailstock The Tailstock consists of an upper and lower casting , which allows the tailstock to modify the axis of the lathe for long taper machining. Tailstock misalignment is corrected by aligning the the upper casting to the lathe axis. The spindle bore is manufactured with a Morse taper, (5/8 TPF), and holds tools such as drills, reamers revolving dead centers etc. The Tailstock can be used to assist in producing long low taper angle tapers Lathe Components Starting Clutch Figure 21 - Starting clutch lever. Clutch Mechanism Lathe starting clutches can be either: Electronic Mechanical  OBJECTIVE 4 EXPLAIN WORKHOLDING DEVICES USED ON THE LATHE  Work Holding Devices Important features of work holding devices: They must hold the work securely They must hold the work accurately They must be convenient and quick to use. Lathe Components DEAD AND LIVE CENTERS The solid dead center is A half center allows space made of hardened steel or for a facing tool carbide and is considered the more accurate than the revolving dead center. Figure 24 - Solid dead centres. Pg. 17 Figure 27 - Drive plate. Headstock Center Rotates with the spindle , mounted within the spindle ( Morse Taper) Solid Centers that are mounted in the Headstock are called “Live Centers” Solid Centers that are mounted in the tailstock are called “Dead Centers” Figure 23 - Live centre in headstock spindle.  (Drive Plate) (Dead Center) Requires the use of high (Live –Dead center) pressure lubricant on this Dead Center (Non-Rotating) Never part off a workpiece being turned between centers. Figure 22 - Workpiece held between centres. Parting tools Correct Incorrect Important : Never part a workpiece running between centers Bearing Centers Figure 25 - Rotating dead centre. Bearing Center Long Nosed Center Face Drive Center Face driving center Bell Center Lathe Drive Dogs companion equipment to the Dead and Live Center Figure 26 - Lathe dogs.  Chucks Four main types of chucks Four jaw independent chuck Collet chuck Magnetic chuck Three jaw universal chuck Note: Chucks are sized by the diameter of their body Chucks are sized by the outside diameter of the chuck body. An 8 inch would have an outside diameter of 8 inches. Figure 28 - Three jaw universal chuck. Figure 29 - Scroll plate inside three jaw chuck. Figure 30 - Number on jaw and slot. Figure 31 - Inside jaws. Component Mounting in 3 Jaw external grip Figure 32 - Outside jaws. Soft Jaws  3 Jaw Universal Chuck All three jaws move at once. A scroll plate on the inside of the chuck engage the teeth on the back of the jaw. The Jaws are made as a matching set. The jaws must be installed in the proper order. The independent jaw movement of the four jaw chuck allows the workpiece to be dialed in until it runs perfectly true. Figure 33 - Four jaw independent chuck.  4 Jaw Independent Chuck All four jaws move independently. The work piece can be centered more accurately than in the 3 jaw. The jaws are reversible. The 4 jaw supplies more holding power than the 3 jaw. Collets are used on stock that has a good finish such as cold rolled and T&G. They are generally rated for higher RPM than other chucks. Figure 37 - Collet chuck. Magnetic chucks are used for holding flat magnetic work that cannot be held any other way. They should only be used for light cuts only. Figure 38 - Magnetic chuck.  Faceplates Face plates are used to hold work that would be difficult or impossible to hold in a chuck. They have T-Slots that enable the work to be clamped to the surface of the plate. Counter weights are required when machining off center work. Faceplates  Mandrels Mandrels are used to grip a workpiece by the bore to permit the outside diameter to be machined. There are five types of mandrels: Solid mandrels Expansion mandrels Gang mandrels Threaded mandrels Taper shank mandrels Mandel Types Expansion Mandrel Solid Mandrel Specialty Tapered Drive - Solid Mandrels The solid mandrel has a taper per foot of 0.006 - 0.008. Comes in standard fractional sizes. Identified by stamp on the large end. It is used to turn parts such as bushings and pulleys where the OD must run true to the ID. Always turn towards the large diameter. Figure 39 - Solid mandrel. Expansion Mandrels The taper on the mandrel matches the taper on the sleeve. Part must be pressed on the arbor. Figure 40 - Expansion mandrel  Morse Taper Used when multiple parts are being machined. Figure 41 - Gang mandrel. The part to be machined must have a matching internal thread. Cannot be machined with reverse spindle rotation. Figure 42 - Threaded mandrel.  OBJECTIVE 5 DESCRIBE LATHE TOOL HOLDING DEVICES Figure 57 - Square quick change tool-post. Figure 58 - Multi-position quick change tool post. END