• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Manufacturing technology   i 1 18 - copy
 

Manufacturing technology i 1 18 - copy

on

  • 2,116 views

 

Statistics

Views

Total Views
2,116
Views on SlideShare
2,116
Embed Views
0

Actions

Likes
1
Downloads
423
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Manufacturing technology   i 1 18 - copy Manufacturing technology i 1 18 - copy Presentation Transcript

    • Machining
    • Machining• Machining – A subtractive process used to get desired shape, size, and finish by removing surplus material in the form of chips by a cutting tool and by providing suitable relative motion between the workpiece and cutting tool – Process of finishing by which jobs are produced to the desired dimensions and surface finish by gradually removing the excess material from the preformed blank in the form of chips with the help of cutting tool (s) moved past the work surface (s).
    • • Machining requirements
    • Machining ProcessesUsing SINGLE-Point Using MULTI-Point Using ABRASIVES Cutting Tools Cutting Tools as Cutting Tools Turning  Milling  Grinding  Step Turning  Drilling  Honing  Taper Turning  Reaming  Lapping  Form Turning  Knurling  Polishing  Contour Turing  Sawing  Buffing Facing Necking Parting-Off Boring Unconventional Machining  Counter-Boring Processes  Counter-Sinking AJM, USM, WJM Shaping ECM, ECG Planing CHM IBM, PAM, EDM, LBM, PAM
    • Machine tool• A machine tool is a non-portable power operated and reasonably valued device or system of devices in which energy is expended to produce jobs of desired size, shape and surface finish by removing excess material from the preformed blanks in the form of chips with the help of cutting tools moved past the work surface (s)• Physical functions of a Machine Tool in machining are: – firmly holding the blank and the tool – transmit motions to the tool and the blank – provide power to the tool-work pair for the machining action – control of the machining parameters, i.e., speed, feed and depth of cut
    • Basic Machine ToolsCentre lathes – Cylindrical shapes – Manual lathes or CNC
    • Basic Machine ToolsCentre lathes External Internal
    • Basic Machine ToolsShaping machine• Ram: it holds and imparts cutting motion to the tool through reciprocation• Bed: it holds and imparts feed motions to the job (blank)• Housing with base: the basic structure and also accommodate the drive mechanisms
    • Basic Machine ToolsShaping machine• Power drive with speed and feed change mechanisms• Shaping machines are generally used for producing flat surfaces, grooving, splitting etc.
    • Basic Machine ToolsPlaning machine• In planing the job reciprocates for cutting motion and the tool moves slowly for the feed motions unlike in shaping machine.• Planing machines are usually very large in size and used for large jobs and heavy duty work.
    • Basic Machine ToolsDrilling machine• Drilling (originating or enlarging cylindrical holes)• Boring, counter boring, counter sinking etc.• Cutting internal threads in parts like nuts using suitable attachment
    • Basic Machine ToolsDrilling machine• Column with base: it is the basic structure to hold the other parts• Drilling head: this box type structure accommodates the power drive and the speed and feed gear boxes• Spindle: holds the drill and transmits rotation and axial translation to the tool for providing cutting motion and feed motion• Pillar drill, column drill, radial drill, micro-drill etc.
    • Basic Machine ToolsMilling machine• Flat surfaces• Slotting• Slitting• Grooving• Parting• Forming
    • Classification of Machine Tools1. Direction of major axis – horizontal center lathe, horizontal boring machine etc. – vertical – vertical lathe, vertical axis milling machine etc. – inclined – special2. Purpose of use – general purpose – e.g. lathes, milling, drilling machines etc. – single purpose – e.g. facing lathe, roll turning lathe etc. – special purpose – for mass production3. Number of spindles – single spindle – center lathes, milling machines etc. – multi-spindle – gang drilling machines etc.
    • Classification of Machine Tools4. Degree of automation – Manual – e.g. lathes, drilling machines etc. – Semi-automatic – e.g. turret lathe – Automatic – e.g., CNC Drill, CNC Mill, CNC lathe etc.5. Type of automation – fixed automation – e.g., single spindle and multispindle lathes – flexible automation – e.g., Machining Centers6. Precision – Ordinary – High precision
    • Classification of Machine Tools7. Size – Heavy duty – e.g., heavy duty lathes (e.g. ≥ 55 kW), boring mills, etc. – Medium duty – e.g., lathes (e.g. – 3.7 ~ 11 kW), column drilling machines etc. – Small duty – e.g., table top lathes, drilling machines, milling machines. – Micro duty – e.g., micro-drilling machine etc.8. Configuration – Stand alone type – most of the conventional machine tools. – Machining system – e.g., machining center, FMS etc.
    • Cutting Tool• Removes excess material through direct mechanical contact• Tool moves along the workpiece at a certain velocity (cutting speed – V) and a depth of cut (to) to produce a chip just ahead of tool by shearing the material continuously along the shear planeTool material Selection depends on:• Work material (hardness, chemical and metallurgical state)• Part features (geometry, accuracy, finish, surface-integrity)• Machine tool characteristics (rigidity, horsepower, speed, feed , precision)• Support system (Operator, sensors, controls, method of chip removal, lubrication, maintenance)
    • Cutting ToolTool Selection (material, geometry, cutting conditions)
    • Cutting Tool• Tool Material Characteristics – Hardness – Toughness – Wear Resistance – Chemical Inertness – Resistance to bulk deformation – Thermal Properties – High Stiffness – Geometry – Finish
    • Cutting Tool Hardness of cutting materialsHardness—resistance to deforming and flattening
    • Toughness—resistance to breakage and chipping Cutting Tool Wear resistance—resistance to abrasion and erosion
    • Cutting Tool
    • Cutting ToolCast-cobalt alloys (1915)
    • Cutting Tool
    • Cutting Tool• Tool steels• HSS• Coated HSS• Cast Cobalt Alloys• Carbides / Sintered Carbides• Coated Carbides• Ceramics• Cermets• Diamonds• Polycrystalline CBN’s – and many more…………..
    • Cutting ToolTool steels• Carbon and low-/medium-alloy steels• Steel is considered to be carbon steel: – when no minimum content is specified or required for Cr, Co, molybdenum, Ni, Ti, W, V or zirconium etc. – when the specified minimum for copper does not exceed 0.40 percent; – when the maximum content specified is less than Mn - 1.65, Si - 0.60, Copper - 0.60. – steel which is not stainless steel• 0.9 to 1.3% carbon• With increase in carbon content, steel become harder and stronger
    • Cutting ToolTool steels• With increase in carbon content, steel become lesser ductile and melting point decrease• Hardness loss at 200 0C• Mo and Cr increases hardenability• Mo and W improves wear resistance• Applications – Drills, Taps, Dies etc. – Low speeds
    • Cutting ToolHSS• Good wear resistance, hardenability and hot hardness• Good toughness and resistance to fracture• Good cutting at 400 0C• Easy fabrication• Types – Molybdenum (M series) • 10% Mo with Cr, V, W, Cr and Co • High abrasion resistance than t series • Less Distortion than T series • Cheaper than T series – Tungsten (T series) • 12-18% W, Cr, V and Co (18-4-1 W-Cr-V)• Used for complex tool geometries
    • Cutting ToolTiN coated HSS• Film thickness 0.00254 - 0.00508 mm• 10-20% higher cutting speeds than HSS• Gear cutters, drills, bandsaw, circular saw blades, form tools, inserts etc.• Reduced tool wear• High hardness• PVD
    • Cutting ToolCast Cobalt Alloys• Cobalt rich, chromium-tungsten-carbon cast alloys• Stellite tools (Deloro Stellite Company)• Non-magnetic and corrosion-resistant cobalt alloy• W or Mo and a small amount of carbon• Retain hardness to much greater temperatures• 25 % higher cutting speeds than HSS• Cast to shape• Used only for single point tools or saw blades
    • Cutting ToolCarbide or Sintered Carbides• Types: – Tungsten carbide (WC bonded together in a cobalt matrix) • 1-5 µm WC particles are combined with cobalt in a mixer, then presses and sintered into the desired insert shapes. • Cemented carbides Sintered Carbides • With increase of Co – toughness increases but there is decrease in strength, hardness and wear resistance • Machining steels, CI, nonferrous and nonmetals – Titanium Carbide (TiC in Ni-Mo alloy matrix) • Higher wear resistance than WC • Lesser toughness than WC • Machining hard materials like steels, CI • Higher speeds than WC • Finishing and semifinishing ferrous alloys • Auto industry using Ni-Mo binder
    • Cutting ToolInserts• Individual cutting tools with several cutting points• Sq inserts (8 cutting edges), triangular insert (6 cutting edges)
    • Cutting ToolInserts are clamped on tool shank with various locking mechanisms• (a) Clamping• (b) Wing lock pins• (c) Thread-less lock pins - secured with side• (d) Brazed on a tool shank
    • Cutting ToolChip Breaker• Continuous chips are undesirable as they are a potential safety hazard• Cutting at low speed may lead to welding of chips to tool face• Ideal chip – Shape of letter “C” or number “9” and fits within 25 mm square block• Procedure used for breaking chips intermittently is with use of chip breaker
    • Cutting ToolChip Breaker(a) tightly curled chip(b) chip hits workpiece and breaks(c) continuous chip moving away from workpiece(d) chip hits tool shank and breaks off
    • Cutting ToolChip Breaker• Controlling chip flow• Eliminating long chips• Reducing vibration and heat
    • Cutting ToolChip Breaker• Chip breaking in softer materials like Al include machining at small increments and then pausing.• In shaping, milling or other such intermittent operations chip breakers are not required
    • Cutting Tool• American National Standards Institute (ANSI) – C-1 to C-8• ISO Standards – P, M and K Classification of Tungsten Carbides
    • Cutting ToolISO Classification of Carbide Cutting Tools According to Use
    • Cutting ToolCoated Carbide tools• Coating increase tool life by 200-300 times• Coating increase 50-100% in speed of the same tool life• 80-90 % of carbide tools are coated• Bulk tool material can be tough, shock resistant carbide that can withstand high temperature plastic deformation and resist breakage• Thin chemically stable, hard refractory coating of TiC, TiN, TiCN or Al2O3, Diamond, TiAlN, CrC, ZrN etc.• Fine grained coatings• Free form binders and porosity• Low coeff. of friction for coating – non adherence of chips on rake face
    • Cutting ToolCoated Carbide tools• Single or multiple• Multiple coating provide stronger metallurgical bond between coating and substrate• For multiple coating: – Innermost layer should bond with substrate – Outermost layer should resist wear – Intermediate layer should bond well and be compatible with both layers
    • Cutting Tool
    • Cutting ToolCeramics (White or cold-presses ceramics)• 1950• Pure Aluminium oxide, Al2O3, or SiC• Pressed into insert shapes under high pressure• TiC and ZrO may be added to improve toughness and resistance to thermal shock
    • Cutting ToolCeramics• Particulates or whiskers• 2 to 3 times cutting speed than WC• High hardness and chemical inertness• Hard and brittle – require rigid tool holders and machine tools• Less tendency to adhere to metals during machining – good SF• Used for high speed cutting/finishing of super-alloys and high strength steels• Not suitable for Al, Ti as they react with alumina based ceramics
    • Cutting ToolCermets (Ceramics + Metal)• Black or hot-pressed ceramics• Mix of 70% aluminium oxide and 30% TiC• Intermediate performance between ceramics and carbides
    • Cutting ToolPolycrystalline CBN• High hardness (Knoop 4700 at 20 oC 4000 at 1000 oC)• Low chemical reactivity• 0.5-1 mm layer of PCBN is bonded to a carbide substrate by sintering under pressure.• Carbide provides toughness – CBN provides high wear resistance and cutting edge strength• Used for automotive industry Difficult-to-machine materials• Used for aerospace materials• Higher cost than ceramics tools or cemented carbides but tool life is 5-7 times that of a ceramic tool
    • Cutting ToolPolycrystalline CBN PCBN Tips Solid PCBN
    • Cutting ToolDiamond• High Wear resistance, low tool-chip friction, sharp cutting edges• Used for fine surface finish and dimensional accuracy• Brittle - Light and uninterrupted finishing cuts• High speed machining and fine feeds• Single-crystal diamond tool – machining optical mirrors• Polishing is not required after machining• Polycrystalline diamond tools (compacts or industrial diamonds) – small synthetic crystals, fused by high pressure and temperature to a thickness of .5-1 mm and bonded to a carbide substrate
    • Tool Geometry
    • Tool Geometry• One or more sharp cutting edges• Connected to cutting edge – two surfaces – Rake face – directs the flow of newly formed chip and is oriented at an angle α (rake angle – measured relative to plane perpendicular to work surface) • Positive rake angle – reduces cutting force – Flank – provides a clearence between tool and newly generated work surface, thus protecting the surface from abrasion (relief angle)
    • Tool Geometry• Tool point (nose radius) – The point (rounded to a certain radius) on tool penetrates below the original work surface
    • Cutting Condition• Cutting speed ‘v’• Tool movement (lateral across the work) – feed ‘f’• Penetration of cutting tool below the original work surface – ‘DOC’ RMR = vfd where, RMR = material removal rate (mm3/min), v = cutting speed (mm/s), d = DOC (mm)
    • Types of Chips• Chip has two surfaces Shiny – in contact with rake face (rubbing of chip as it moves up the tool face) Rough or jagged – no contact with any solid body• Primary shear Zone – along the shear plane• Secondary Zone – shearing action after chip has been formed (results from friction between chip and tool along the rake face)• Continuous• Continuous with BUE• Serrated• Discontinuous
    • Types of Chips• Continuous – Good surface – Steady cutting force – Undesirable in automated machining – Formed in ductile materials at high cutting speeds and high rake angles
    • Tool GeometryContinuous with BUE• Ductile materials at low-to-medium cutting speeds, friction between tool and chip tends to cause portions of work material to adhere to rake face of tool near the cutting edge• BUE forms and grow, then becomes unstable and breaks off• Detached BUE sometimes takes away portions of tool rake face (may lower tool life)• Detached BUE that are not carried off may imbed in newly created work surface causing roughness• Thin stable edge protects tools
    • Types of ChipsSerrated (segmented, non-homogeneous)• Difficult-to machine- materials like Ti, Ni-base super alloys at higher cutting speeds.• Saw-tooth appearance (semi-continuous)• Produced by cyclical chip formation of alternating high shear strain followed by low shear strain
    • Types of ChipsDiscontinuous• Brittle materials (like CI) at low cutting speeds• Chips forms as separate segments• Fluctuating cutting forces• Irregular texture to machined surface• Desirable for ease of chip disposal
    • Types of ChipsType of Chip ?
    • Orthogonal Cutting• Cutting edge is perpendicular to direction of cutting speed• Force by tool forms chip in material by shear deformation along shear plane (angle Ø with work plane)• Cutting edge is positioned at a certain distance below original work piece (to - chip thickness prior to chip formation• When chip forms along shear plane its thickness increases (tc)• Chip thickness ratio ‘r’ – r = to/tc
    • LatheLathe• Oldest Machine Tool invented• Principal form of surface produces – cylindrical• Turning - Workpiece is rotated, while single-point cutting tool removes material by traversing in direction parallel (cylindrical jobs) to the axis of rotation
    • LatheTypes: – Engine lathe – Tool room lathe – Speed lathe – Turret lathe – Automatic lathe – Numerical control latheCentre Lathe• Generally workpiece is clamped by centres in lathe• Also called as Engine lathe (driven by steam engines)• Heavy duty machine tools with all the components have power drive for all tool movements except on compound rest• Most engine lathes are equipped with chip pans and a built-in coolant circulating system
    • LatheTool room lathe• Tool making / smaller parts• Greater accuracy and usually a wider range of speeds and feeds than engine lathes.• Designed to have greater versatility to meet the requirements of tool and die work• Generally used for machining smaller parts• High range of sizes
    • LatheSpeed Lathe• Speed lathes usually have only a headstock, a tailstock, and a simple tool post• Usually three or four speeds• Mainly used for wood turning, polishing, or metal spinning• Spindle speeds up to 4000 rpm.
    • LatheTurret Lathe• Hexagon turret replaces the tailstock• Turret used for mounting tools and feed into the work piece• Turret lathes Use the 11 station tooling and so as to increase production rate by reducing tool changing time .• Six tools can be mounted on the hexagon turret• Turret can be rotated about the vertical axis to bring each tool into the operating position
    • Lathe
    • Lathe• Headstock• Spindle• Live centre• Gear box• Feed Gear box• Tailstock• Carriage• Cross slide• Tool post
    • LatheLathe Specifications
    • LatheWork Holding Devices• Suitable locations• Effective clamping• Support• Face plate: for holding irregular shape w/p• Lathe centers: for holding long jobs• Chuck: – 3 jaw chuck for circular or hexagonal section – 4 jaw chuck for irregular shapes – Magnetic chuck for holding soft metal
    • LatheWork Holding Devices
    • Lathe
    • LatheMandrel – for holding hollow disc shape w/p for machining of side faces
    • LatheCollet – for holing small diameter tool and work pieces
    • Lathe Tool Geometry• Tool cross-section – square or rectangular• Shank (supported in tool post of lathe) – part of tool, on one end of which cutting point is formed α=0 -α +α Positive Rake Zero Rake Negative RakePositive rake – helps reduce cutting force and thus cutting power requirementNegative rake – to increase edge-strength and life of the toolZero rake – to simplify design and manufacture of the form tools.Clearance angle must be positive (3o ~ 15o)
    • Lathe Tool GeometryKinds of tools and surface
    • Lathe• Right/Left tool – Tools have primary cutting edge by means of which the direction of the movement of tool for removing of metal is indicated – Tool is termed as right, right palm is placed on tool, the direction of thumb indicates the direction of tool motion (tool towards the headstock)
    • Lathe Tool Geometry• Zero or negative rake are used for better heat conductivity on carbide, ceramic PCD and PCBN tools• Negative rake angle increase tool forces, it keeps tool in compression and provides added support to cutting edge. This help in making intermittent cuts and in absorbing impact during initial engagement of tool
    • Lathe Tool GeometrySystems of description of tool geometry• Tool-in-Hand System – where only the salient features of the cutting tool point are identified or visualized (no quantitative information)• Machine Reference System – ASA system
    • Lathe Tool GeometryMachine Reference System• American Standards Association (ASA) system• Geometry of a cutting tool refers mainly to its several angles or slope of its salient working surfaces and cutting edges. Those angles are expressed w.r.t. some planes of reference.• Machine Reference System (ASA) is based on three planes of reference and three coordinates of reference. These references are chosen based on the configuration and axes of the machine tool concerned.
    • Lathe Tool Geometry
    • Lathe Tool Geometry• Back-rake angle: Angle b/w face of tool and base of shank (measured in a plane through the side cutting edge, and at right angle to base)• Side-rake angle: Angle b/w face of the tool and the base of shank (measured in a plane perpendicular to the base, to the side cutting edge) The side rake and back rake angle combines to form effective rake angle (true rake or resultant rake)• End-relief angle: Angle between the portion of the end flank immediately below the end cutting edge, and a line drawn through this cutting edge perpendicular to the base (measured in plane perpendicular to the end flank)• Side-relief angle: Angle between portions of the end flank immediately below the side-cutting edge and a line drawn through this cutting edge perpendicular to the side flank Relief angles affects tool life and surface quality of workpiece
    • Lathe a. 3D views of toolb. Oblique view of tool from cutting edge
    • Lathe Tool Geometry• Side and end cutting-edge angles defines nose angle. Side cutting Edge angle controls the width and thickness of chips• Nose radius has a major influence on surface finish. High nose radius decrease tool wear and improves surface finish.
    • LatheTurning is the process of machining external cylindrical and conical surfaces. – Straight turning: for producing cylindrical shapes – Taper turning: for producing conical shapes – Facing: making edges square and clear – Chamfering: slightly tapering and rounding off of edges – Threading: for producing threads – Drilling: for creating /producing hole – Boring: for enlarging hole and correcting shape – Parting off or necking: separating or making square groove – Knurling: making impression for firm gripping – Reaming: finishing purpose
    • Lathe
    • Lathe - TurningTurning CutsRoughing – As heavy as proper chip thickness, tool life, machine power and work material properties permit – Slow speeds for hard workpiecesFinishing – Light, usually less than (0.015 in) – Usually same tool is used for roughing and finishing
    • Lathe - Turning
    • Lathe - TurningCutting speed – V (fps)DOC d = (D1-D2)/2Length of Cut = Distance travelled ‘L’ + Allowance ‘A’Feed - fRpm value of machine tool - N = 12V/πD1Cutting Time – T = (L+A)/fNMRR = L(πD12- πD22)/4 (L+A)/fNNeglecting A and substituting NMRR = 12Vfd (d is very small as compared to D1(d = 1))
    • Lathe - TurningCutting speed – V (fps)DOC d = (D1-D2)/2Length of Cut = Distance travelled ‘L’ + Allowance ‘A’Feed - fRpm value of machine tool - N = 12V/πD1Cutting Time – T = (L+A)/fNMRR = L(πD12- πD22)/4 (L+A)/fNNeglecting A and substituting NMRR = 12Vfd (d is very small as compared to D1(d = 1))
    • Lathe – Taper Turning• Cutting tool is fed at an angle to the axis of rotation producing an external/internal conical surface.• Tapers generally specified in degrees of included angle between the sides (or rate of change in diameter along the length mm/mm)Taper tuning can be performed by using:• Swiveling of compound rest (short and steep tapers)• Form tools• Offsetting tail stock• Taper turning attachment (fine taper-ness)• NC lathe with programmed movement of tool
    • Lathe – Taper Turning Swiveling of compound rest (short and steep tapers) Tool is set at half of taper angle w.r.t. lathe axis and moved with compound rest onlyManual Feed (non-uniform)Short and steep tapersLimited movement of comp. restLow productivityPoor surface roughness
    • Lathe – Taper TurningSwiveling of compound rest (short and steep tapers)
    • Lathe – Taper TurningForm ToolsFeed is given by plunging the tool directly into the workShort tapers like chamferingTool may vibrate excessively on long tapersPoor surface quality in long tapers
    • Lathe – Taper TurningOffsetting tail stockOffsetting results in inclination in job’s axis of rotation by half angle of taperThe feed is given parallel to guide ways
    • Lathe – Taper TurningOffsetting tail stock
    • Lathe – Taper TurningOffsetting tail stock
    • Lathe – Taper TurningOffsetting tail stock
    • Lathe – Taper TurningTaper turning arrangementSeparate slide way is arrange at rear of cross-slide. This slide can be rotated at angleThe cross-slide is made free by disconnecting it from lead screw
    • Taper turning attachment • Cross slide is made free and tool is moved with help of attachme nt at an angle
    • Lathe-BoringBoringEnlarging of an existing holeCorrection of eccentricityHoles may be bored straight, tapered or irregular threadsSimilar to internal turning while feeding tool parallel to rotation axis of workpieceHigher clearance angle and lower length to diameterBoring bar is used
    • Lathe-BoringBoringCutting Time – T = (L+A)/fNRpm value of machine tool - N = 12V/πD1MRR = L(πD12- πD22)/4 (L+A)/fNMRR = 12Vfd
    • Lathe-FacingFacingProducing flat surfaceTool is fed across the end of rotating workpieceTool feeds perpendicular to axis of rotating workpieceCutting speed is determined from largest diameter on workpieceTool point must be set exactly at height of center on workpieceLength of cut - L = D1/2 (rod) - L = (D1-D2)/2 (tube)
    • Lathe-Facing
    • Lathe-FacingFacingProducing flat surfaceTool is fed across the end of rotating workpieceTool feeds perpendicular to axis of rotating workpieceCutting speed is determined from largest diameter on workpieceTool point must be set exactly at height of center on workpieceLength of cut - L = D1/2 (rod) - L = (D1-D2)/2 (tube)
    • Lathe-FacingCutting Time – T = (L+A)/fN = (D1/2 + A)/fNRpm value of machine tool - N = 12V/πD1MRR = π D12dfN substituting N, L=D1/2 MRR = 6Vfd
    • Lathe-FacingEnd facing: facing by tool moving radially outward from the centerShoulder facing: facing the stepped cylindrical work piece
    • Lathe - PartingNecking is a making partial cut-off
    • Cut-off tool is used Lathe - PartingOne section of workpiece is severed from remainingTool should be set exactly at height of axis of rotationTool is fed perpendicular to rotational axisLength of cut - L = D1/2 (rod) - L = (D1-D2)/2 (tube)Cutting Time – T = (L+A)/fN = (D1/2 + A)/fNRpm value of machine tool - N = 12V/πD1MRR = π D12dfN substituting N, L=D1/2 MRR = 6Vfd
    • Lathe - DrillingDrillingTool (Drill) can be mounted on the tailstock of engine lathes or turrets of turret lathesFed by hand against a rotating work piece along the axis of latheCoolant can be usedOccasional withdrawal to clear chips and delivery of coolant to cutting edge
    • Lathe - ReamingSimilar to drilling on latheIt is semi-finishing operation thatenlarges an existing holeTool is rotated and fed alongrotational axis.
    • Lathe - KnurlingKnurlingRoughening the surface of workpiece for better gripping.Generally a cold-forming processProcess involves pressing of twohardened rolls against the rotatingwork piece with sufficient force toform impression (the knurl) likeraised diamond pattern.
    • Lathe - KnurlingKnurling
    • Contour turningThe tool follows a contour creating a contoured form on the turned part instead of parallel to the axis. Cross slide is made free to follow the path of contour.Form TurningCutting edge of Tool has a Specific Form or Shape and is fed radially inward towards the axis of rotating work piece.
    • Chamfering The tool is fed radially inward used to cut an angle on the corner of the cylinder, forming a chamfer to avoid sharp edges.
    • Drilling• Drilling is most common single machining operation• Drilling makes up 25% of machining• Drilling occurs at the end of a tool
    • Drilling1. A small hole is formed by the web—chips are not cut here in the normal sense.2. Chips are formed by the rotating lips.3. Chips are removed from the hole by the screw action of the helical flutes.4. The drill is guided by lands or margins that rub against the walls of the hole. Twist Drill
    • DrillingTwist Drill
    • Drilling
    • Drilling• Rake angle of a drill varies along the cutting edges (lips) – Negative close to point – Equal to helix angle out at lip • Generally rake angle is 24o • High speed drilling - rake angle is 30o • Soft materials (plastics) – rake angle is 0o to 20o• Cone angle – affects direction of flow of chip across the tool face and into the flute – Generally cone angle of 118° – Brittle materials (gray CI, Mg alloys) 90° to 118° – Ductile materials (Al alloys) 118° - 135°
    • Drilling• The most common drills are twist drills• Twist drills have three parts – Body: consisting of spiral grooves called flutes, separated by lands – Point: a wide variety of geometry are used – Shank: a straight or tapered section where the drill is clamped.
    • Drilling(a) straight shank with tang,(b) tapered shank with tang,(c) straight shank with whistle notch,(d) straight shank with flat notch.
    • Drilling Cutting Speed at drill center is low (approaching zero)Cutting speed at outer tips is highest Intersection of web and cone produces a straight line chisel end
    • Drilling• Straight line chisel point causes drills to “walk” along the surface• This effect is counter by using centering techniques – Center punches – Pre-drilled guide holes for large holes• Specialized tips are used to produce self centering holes where hole position is critical. – Helical tips – Four-facet tips – Racon – Bickford – Center core, or slot drills
    • Drilling
    • Drilling
    • DrillingCenter Core DrillTwin carbide tips brazed on steel shank and a slot in center
    • Drilling
    • Drilling• Specialty Drills – Hole cutters: used for holes in sheet stock – Step drill – used for two or more diameters – Subland drills: used for multi diameter holes – Indexable drills: used for high speed shallow holes in solid stock – Centre drill bit with internal coolant – Micro drills (pivot drills): used for holes 0.02 to 0.0001 inch diameter where grain boundaries and inclusion produce non-uniform material properties
    • DrillingHole Cutters• When cutting large holes in sheet stock, a hole cutter is used• Hole cutters have a pilot drill in the center used to accurately locate the center• Also called a hole saw
    • Step Drill DrillingSingle set of flutes and is ground to two or more diametersSubland DrillSeparate set of flutes on a single body for each diameter.
    • DrillingIndexable Drills
    • Drilling• Microdrills 0.0001 in – 0.125 in
    • DrillingDrill Chucks• Small Drill Press – Chuck is permanantly attached• Large Drill Press – Chuck has tapered shank that fits into the taper on machine spindle• Chucks use chuck keys/collet-type holders
    • DrillingDrill Chucks
    • Machine Tools for Drilling• Drilling can be performed on: – Lathes – Vertical mills – Horizontal mills – Boring machines – Machine centers• Specialized machines designed specifically for drilling called “drill presses”
    • DRILLING MACHINE Drilling is Most Commonly Performed on a Drill Press. DRILL PRESS Consists of Following Parts 1. Base, 2. Column 3. Power-Head 4. Spindle 5. Worktable These may be bench or floor mounted depending on the size  Drill can be fed manually or Upright Drill Press. automatically
    • TYPES of DRILLING MACHINES MAIN TYPE Applications 1. BENCH Holes up to 0.5 in. Diameter can be Drilled. Very High Speed up to 30,000 rpm 2. UPRIGHT Speeds Ranges from 60 to 3500 RPM 3. RADIAL For Large Workpieces that Cannot Easily be Handled Manually.
    • TYPES of DRILLING MACHINES MAIN Applications TYPE 4. GANG Mass Production variety of purposes such as Holes of Different Sizes, Reaming, Counterboring, on a Single Part.
    • TYPES of DRILLING MACHINES MAIN Applications, Designation TYPE 5. MULTI- Mass Production Machines with as many SPINDLE as 50 Spindles Driven by a Single Power head and Fed Simultaneously into Work. 6. DEEP- For Drilling Long (Deep) Holes in HOLE Rifle Barrels, Connecting Rods, and Long Spindles.