1. MT-284 MANUFACTURING PROCESSES INSTRUCTOR: SHAMRAIZ AHMAD MS-Design and Manufacturing Engineering Shamraiz_88@yahoo.com Topic: Cutting Tools and Cutting Fluids

2. Today’s Lecture Single point cutting tool Multi point cutting tools Tool life & wear, Tool failure, Factors affecting tool life, Measuring tool life Tool material & its characteristics Cutting fluids, Purposes, Types & properties of cutting fluids.

3. Cutting Tools Tool: a device which touches the work piece to remove material, is called tool. Hand tool: a hand operated tool is called hand tool like hammer and screw driver. Machine tool: a tool operated through machine is called machine tool. Like Turning Machines, Sawing Machines, Drilling Machines Single point cutting tool: performing cutting at one point of contact. Common single-point tools include knives, chisels Multi point cutting tool: The multiple-point tool has a series of single-point tools arranged on a cutting device. Most often, these single-points are arranged in a pattern. For example, a circular saw has teeth evenly spaced around the circumference of the blade

4. What is a Cutting Tool A cutting tool is any tool that is used to remove metal from the work piece by means of shear deformation. It must be made of a material harder than the material which is to be cut, and the tool must be able to withstand the heat generated in the metal cutting process. Two basic types – Single point – Multiple point 4

5. Single Point Cutting Tool

6. Multi Point Cutting Tool

7. Cutting Tool and its Failure Important aspects of cutting tool 1.Tool Material – Appropriate tool Material for specific cutting operation 2.Tool Geometry - Optimizing Geometry for tool material and operation. High forces and high temperature creates harsh environment for the cutting toll. High forces- cause tool fracture High temperature- the tool material softens and fails Gradual wear at rake face and at flank also causes tool failure finally

8. Cutting Tool Wear Crater Wear A concave section on the rake face of the tool, formed by the action of chip sliding against the surface. High stresses and temperature contributes to cause the Crater type of wear. Flank Wear Occurs the flank or relief face of the toll results from rubbing between newly formed surface and flank face of the tool adjacent to the cutting edge.

9. Tool Wear Mechanism of Tool wear: Abrasion: Mechanical wearing action due to hard particles in work material removing small portion of the tool. Present in both types of wear but more significant in flank wear. Adhesion: Due to high temperature and pressure welding occurs between two metals. Small particles from rake face are broken away with the chip. Diffusion: Exchange of atoms across a close contact boundary between two materials. This causes Surface more susceptible for abrasion and adhesion. It is the principle cause of crate wear. Chemical Reaction: at High temperature the clean surface of tool may oxidize and result in chemical reaction with part material or cutting fluid. Plastic Deformation : the cutting forces acting the cutting edge at high temperature may cause the edge to deform plastically, making it more vulnerable for abrasion.

10. Tool Life Tool Wear is the function of cutting time: Tool life is defines as the Length of time for which the Tool can be used. Tool life Relationship by Taylor V = cutting speed T = Tool life, n is an exponent that depends on cutting conditions C the constant depend upon Material of tool and work It was observed experimentally that High cutting speed decreases the tool life. Regions of Wear Rapid Wear- Break in Period Uniform Wear- Steady State region Acceleration Wear- Failure Region Parameters, which affect the rate of tool wear – cutting conditions (cutting speed V, feed f, depth of cut d) – cutting tool geometry ( – properties of work material

11. Cutting Tool materials Machining operations are performed using cutting tools. The high forces and rise in temperature during machining create very harsh environment. Such undesired conditions may lead to tool failure. so, development of material that can withstand the forces, temperature and wearing actions is very important. Important Properties Required Tool Material – Toughness-To avoid fracture failure – Red Hardness-Hardness at high temperature. – Wear-Resistance-ability to resist Abrasive wear. – Chemical Stability: No chemical affinity for Work piece material

12. Types of tool materials 1.Tool Steel 2.High speed steel (HSS) 3.Ceramics tools 4.Diamond tools 5.Carbide cutting tool

13. 1. Tool steel Tool steel is define as the Steel, specially prepared for making tools like lathe cutters, milling cutters etc, called tool steel. Tools steel has special features like strength, hardness, toughness, wear resistance and response to heat treatment. Classification: 1. Tool steel may be classified based upon alloy used like:

14. TOOL STEEL Carbon tool steel Alloy tool steel 1. Carbon steel Low carbon steel (.02 to 0.2% carbon) Medium carbon steel (0.2 to 0.6% carbon) High carbon steel ( 0.6 to 1.2% carbon) 2. Alloy steel: Low alloy steel ( alloying element less than 2.5%) Medium alloy steel ( 2.5 to 10% alloy) High alloy steel ( alloys more than 10%)

15. Tool Steel One of the oldest tool materials. Used for drills, broaches,reamers Inexpensive,easily shaped,sharpened No sufficient hardness and wear resistance Limited to low cutting speed operation Do not have sufficient red hardness and wear resistance

16. 2. HIGH SPEED STEEL (alloy steel At is alloy steel capable of maintaining hardness at high temperature, better than high carbon and low alloy steel. HSS were developed to machine at higher speeds. Hardened to various depths. Good wear resistance & relatively in-expensive. High toughness and resistance to fracture make them suitable for high positive rake angle tools. There are two types of HSS: – Molybdenum (M series)- up to 10% Molybdenum – Tungsten (T series)-18% tungsten 95% of all HSS tools are produced at USA.

17. 3. Ceramics tools First used commercially is USA in 1950s. Ceramic tools are composed primarily of fine grained aluminum oxide (Al2O3) pressed and sintered at high temperature and pressure. They are hard, retain their hardness at high temperatures and have a relatively low reactivity with steel. They also have a high resistance to abrasion. Used as grinding wheels, as cutting tool inserts similar to cemented carbide inserts.

18. Ceramics tools Ceramic cutting tools can he used to machine ‘difficult’ materials at really high cutting speeds — sometimes over 2000 m/min. Compare this with the cutting speed for carbon steel cutting tools — 6 m/min. Ceramic cutting tools are very brittle. They can be used only on machines which are extremely rigid and free of vibration.

19. 4. Diamond A precious stone consisting of a clear and typically colorless crystalline form of pure carbon. Hardest known substance. High wear resistance but brittle Ability to maintain sharp cutting edge Single crystal diamond of various carats used for special applications in machining and grinding. Like machining of fiber glass and graphite. It is not used in machining of steel and ferrous metals because of chemical affinity that exist between these metals and Carbon of diamond.

20. 5. CARBIDES tools Carbides are also known as cemented or sintered carbides. They have high machining speed for higher production rates. Carbides are most important, versatile and cost effective tool and die material for a wide range of applications. The two basic groups of carbide used for machining operation are: – Tungsten carbide – Titanium carbide.

21. Carbide tools First used in Germany during WW II as substitute for diamonds Good wear resistance Can machine metals at speeds that cause cutting edge to become red hot without loosing harness 31-21

22. Tool Coating material 2-10 µm coatings are applied by chemical vapor deposition and physical vapor deposition techniques. These are used at high cutting speed, thus reducing the time required. Coated tools improve tool life by as much as 10 times that of uncoated tools. Commonly used coating materials include:  Titanium nitride  Titanium carbide  Titanium carbonitride  Aluminum oxide FIGURE Relative time required to machine with various cutting-tool materials, with indication of the year the tool materials were introduced. Note that, within one century, machining time has been reduced.

23. Cutting Fluids Introduction: The use of cutting fluids in metal cutting was first reported in 1894 by F. Taylor who noticed that cutting speed could be increased up to 33% without reducing tool life by applying large amounts of water in the cutting zone. A very few cutting operations are performed dry, i.e., without the application of cutting fluids. Generally, it is essential that cutting fluids be applied to all machining operations

24. Cutting Fluids Definition: A cutting fluid (coolant)is any liquid or gas that is applied directly to machining operation to improve cutting performance.

25. functions of cutting fluids Primary Functions: 1.Cooling 2.Lubrication 3.Flushing away chips Secondary Functions: 1.Corrosion protection of the machined surface 2.enabling part handling by cooling the hot surface

26. 1. Cooling function Metal cutting operations generate heat due to friction and energy lost deforming the material.heat Heat find its way into one of three places – Work piece, tool, chips Ideally most heat taken off in chips Indicated by change in chip color as heat causes chips to oxidize Fluid Can dissipate at least 50% of heat Created during machining 34-26

27. 1. Cooling function Coolants reduces the effect of heat during cutting which helps to prolong tool life. The capacity to reduce heat depends upon thermal properties (specific heat, thermal conductivity etc) of fluid. Water has high specific heat and thermal conductivity, so used as base in coolant-type cutting fluids. Coolants are used in high cutting speed operation at tool material that are prone to failure. Decrease the temperature at the chip-tool interface by 50 degrees F, and it will increase tool life by up to 5 times. Frequently used in turning and milling operations.

29. 2. Lubrication function Lubricants are usually oil based fluids as oil posses good lubricating qualities. It is used to reduced friction at tool-chip and tool-work interface. It is done through extreme pressure lubrication; which is special form of lubrication in which a thin layer of metal surface is formed through chemical reaction. Compound of sulfur and chlorine in these lubricants produces this layer which helps to separate the tool and chip.

30. 2. Lubrication function Lubricant fluids are more effective at low cutting speed because high speed prevent lubricant reaching at interface. Also high speed cause high temperature due which the oil can vaporize. Lubricants are used in drilling and tapping.

32. 3. Flushing away chips 32 Along with cooling and lubrication the fluids also act to remove chip from work piece and tool. Built-up edge keeps breaking off and re-forming which can induce vibration in machine. This action is applicable to small, discontinuous chips only. Cutting fluid are used to flush away the chip. BUE, Result is poor surface finish, excessive flank wear, and cratering of tool face

33. Secondary functions 1.Corrosion control: as fluid form a thin layer on machined surface which helps to protect metal from rust and corrosion. 2.safe handling of cool part: part handling become safe as the coolant reduces temperature of machined surface.

34. advantages of using cutting fluids Higher surface finish quality and better dimensional accuracy are also obtained from cutting fluids Reduction of tool costs – Reduce tool wear, tools last longer Increased speed of production – Reduce heat and friction so higher cutting speeds Reduction of labor costs – Tools last longer and require less regrinding, less downtime, reducing cost per part Reduction of power costs – Friction reduced so less power required by machining

35. Disadvantages of cutting fluids For certain Machine tools- A costly engineering system is required for applying the fluid The fluid used has to be prepared and after use, filtered for re-use of disposed Some fluids have a health risk if not used correctly causing problems. Some cutting materials are affected by thermal shock e.g. cemented carbides. Use of cutting fluids should be avoided for these materials

36. Characteristics of a Good Cutting Fluid 1.Good cooling capacity 2.Good lubricating qualities 3.Resistance to rancidity(unpleasant taste, smell ) 4.Relatively low viscosity 5.Stability (long life) 6.Rust resistance 7.Nontoxic (poisonous) 8.Transparent 9.Nonflammable 34-36

37. Types of cutting fluids Cutting fluids can be broken into four main categories: 1.cutting oils, 2.water miscible fluids, 3.gasses, and 4.paste or solid lubricants. Water is the best fluid for cooling. It has the best ability to carry heat away. Water, however, is a very poor lubricant and causes rust. Oil is great for lubrication but very poor for cooling. Oil is also flammable.

38. Liquid Cutting Fluids Most commonly used cutting fluids – Either aqueous based solutions or cutting oils Fall into three categories 1.Cutting oils 2.Emulsions ( Water Miscible Oil) 3.Chemical cutting fluids 34-38

39. Types of fluids Cutting Oils cutting oils are not mixed with water. Cutting oils are generally mixtures of mineral oil and animal, vegetable, or marine oils to improve the wetting and lubricating properties. Sulfur, chlorine, and phosphorous compounds are sometimes added to improve the lubrication qualities of the fluid for extreme pressure applications which helps in forming a strong layer on surface.

40. Types of cutting fluids Emulsions (Oil mixed in Water) Emulsion is a term that describes soluble oils in water. An emulsion is a suspension of oil droplets in water. Soluble oils are mineral oils that contain emulsifiers. Emulsifiers (prepared from glycerol etc) are soap-like materials that allow the oil to mix with water. Emulsions (soluble oils) when mixed with water produce a milky white coolant. They combines the coolant and lubricating properties. A typical ratio of water to oil is 30:01. Lean concentrations (more water-less oil) provide better cooling but less lubrication. Rich concentrations (less water- more oil) have better lubrication qualities but poorer cooling.

41. Types of cutting fluids Chemical Fluids Chemical coolants are also miscible cutting fluids. Chemical cutting fluids are the chemicals which are mixed with water easily with the help of wetting agent (surfactants like Alkane Sulphonate). They provide good cooling quality but less lubrication as compared to other fluids. The chemical components in the fluid are used to enhance the lubrication, bacterial control, rust, and corrosion characteristics. The dissolved chemicals includes sulfur and chlorine etc. There are several types of chemical coolants available, including coolants for extreme cutting conditions.

42. Types of fluids Gasses Cutting oils and water miscible types of cutting fluids are the most widely used. Gasses are also sometimes used like Compressed air and inert gasses. Carbon dioxide, Freon, and nitrogen are used sometimes as coolant. Paste and Solid Lubricants Waxes, pastes, soaps, graphite, and molybdenum disulfide may be used. These are generally applied directly to the work piece or tool, or in some cases, impregnated directly into a tool, such as a grinding wheel.

43. Cutting Fluid Contamination and solution Contaminants: Tramp oil (machine oil, hydraulic fluid, etc.) Garbage (cigarette butts, food, etc.) Small chips fungi, and bacteria Solution: Replace cutting fluid at regular and frequent intervals Use filtration system to continuously or periodically clean the fluid Dry machining

44. Thank you