1. CUTTING TOOL TECHNOLOGY
Tool Life
Tool Materials
Tool Geometry
Cutting Fluids

2. Tool Wear TYPES
In general there are four basic types of wear that affect tool life: 1) Abrasion wear: This type of wear is caused by small particles of the workpiece "rubbing" against the tool surface. 2) Adhesion wear: A welding action on the surfaces on the tool and workpiece. The consequent stresses of the cutting process lead to fracture of the weld, causing degeneration of the cutting tool. 3) Diffusion wear: Caused by a displacement of atoms in the metallic crystal of the cutting element from one lattice point to another. This results in a gradual deformation of the tool surface. 4) Oxidation wear. At high temperatures oxidation of the carbide in the cutting tool causes wear of the edge.

3. Taylor Tool Life Equation
Relationship is credited to F. W. Taylor
where v = cutting speed m/min (or m/s); T = tool life min (or s); and n and C are parameters that depend on feed, depth of cut, work material, tooling material, and the tool life criterion used.
n is the slope of the plot
C is the intercept on the speed axis at one minute tool life

4. Tool Life Information for Various Materials and Conditions

5. CUTTING TOOLS REQUIRED PROPERTIES
Tool failure modes identify the important properties that a tool material should possess:
Toughness ‑ ability to absorp sudden forces.
Hot hardness ‑ ability to retain hardness at high temperatures. Decreasing hardness with increasing temperature, called hot hardness. Some materials display a more rapid drop in hardness above some temperatures.
Wear resistance‑ Hardness is the most important property to resist abrasive wear

6. CUTTING TOOLS REQUIRED PROPERTIES
The most important properties of tool steels are:
1. Hardness—resistance to deforming and flattening
2. Toughness—resistance to breakage and chipping
3. Wear resistance—resistance to abrasion and erosion.

7. Improvements in Cutting Tools
Improvements in cutting tool materials have led to significant increases in cutting speeds (and productivity) over the years.

8. CuttingTool Materials and Hot Hardness
Typical hot hardness relationships for selected tool materials
Plain carbon steel shows a rapid loss of hardness as temperature increases. High speed steel is substantially better, while cemented carbides and ceramics are significantly harder at elevated temperatures.

9. CUTTING TOOL MATERIALS HIGH-CARBON STEEL
High-Carbon Steel. Their carbon content ranging from 0.80 % to 1.20 %. Because these tools loose hardness at around 300°C, they are not suitable for high cutting speeds and heavy-duty work, their usefulness being confined to work on soft materials such as wood.

10. CUTTING TOOL MATERIALS High Speed Steel (HSS)
High-speed steels are highly alloyed tool steel capable of maintaining hardness at elevated temperatures (do not lose their sharp cutting edges until around 650°C)
Their hot hardness are better than high carbon and low alloy steels.
One of the most important cutting tool materials
Especially suited to applications involving complicated tool geometries, such as drills, taps, milling cutters, and broaches
Two basic types (AISI)
Tungsten‑type, designated T‑ grades
Molybdenum‑type, designated M‑grades

11. CUTTING TOOL MATERIALS High Speed Steel Composition
Typical alloying ingredients:
Tungsten and/or Molybdenum
Chromium and Vanadium
Carbon, of course
Cobalt in some grades
EXAMPLES
HSS:(18% tungsten (W), 4% chromium (Cr), 1% vanadium (V), and 0.9% C) is considered to be one of the best all-purpose tool steels.
Molybdenum HSS: Molybdenum steels such as containing 6 % tungsten, 6 % molybdenum, 4 % chromium, and 2 % vanadium have excellent toughness and cutting ability.
SUPER HSS: Some high-speed steels have cobalt added in amounts ranging from 2 % to 15 %. Because of the greater cost of this material, it is used principally for heavy cutting operations that impose high pressures and temperatures on the tool.

12. CUTTING TOOL MATERIALS Cemented Carbides Inserts
Class of hard tool material based on tungsten carbide (WC) using powder metallurgy techniques with cobalt (Co) as the binder. Carbide cutting tool inserts are made only by the powder metallurgy technique. It will maintain a cutting edge at temperatures over 1200°C. In addition, it has extremely high compressive strength. However, it is very brittle, has low resistance to shock.
High compressive strength but low‑to‑moderate tensile strength→negative or zero rake angles to make chips apply compressive forces on the rake face instead of tensile forces
High hardness (90 to 95 HRA)
Good hot hardness
Good wear resistance
High thermal conductivity
High elastic modulus ‑ 600 x 103 MPa (90 x 106 lb/in2)
Toughness lower than high speed steel

13. Cemented Carbide Inserts P/M process for making cemented carbide insert tools.

14. Cemented Carbides Non‑steel Cutting Carbide Grades: Two basic types:
Non‑steel cutting grades - only WC‑Co
Steel cutting grades - TiC and TaC added to WC‑Co
Non‑steel Cutting Carbide Grades:
Tungsten carbide inserts (WC-Co) containing only tungsten carbide and cobalt (about 94 % tungsten carbide and 6 % cobalt) are suitable for machining gray cast iron and most other nonferrous nonmaterials except steel.
Properties determined by grain size and cobalt content
As grain size increases, hardness and hot hardness decrease, but toughness increases
As cobalt content increases, toughness improves at the expense of hardness and wear resistance

15. Steel Cutting Carbide Grades:
Cemented Carbides
Steel Cutting Carbide Grades:
Straight WC-Co cutting tools cannot be used effectively to machine steel. It was subsequently discovered that additions of titanium carbide (TiC) and tantalum carbide (TaC) to the WC-Co tool significantly retarted the rate of crater wear when cutting steel because of low coeeficient of friction.
Used for low carbon, stainless, and other alloy steels.
Example: 82 % tungsten carbide, 10 % titanium carbide, and 8 % cobalt.

16. Coated Carbides
Cemented carbide insert coated with one or more thin layers of wear resistant materials (reducing the heat caused by the chip flowing over the tool), such as titanium carbide (TiC), aluminum oxide (Al2O3), or titanium nitride (TiN).
Coating applied by chemical vapor deposition or physical vapor deposition
Coating thickness = 2.5 ‑ 13 m ( to in)
Applications: cast irons and steels in turning and milling operations
Best applied at high speeds where dynamic force and thermal shock are minimal
Triple-coated carbide tools provide resistance to wear and plastic deformation in machining of steel, abrasive wear in cast iron, and built-up edge formation.
Photomicrograph of cross section of multiple coatings on cemented carbide tool

17. Triple Coated Carbide Tools Triple-coated carbide tools provide resistance to wear and plastic deformation in machining of steel, abrasive wear in cast iron, and built-up edge formation.

18. CUTTING TOOL MATERIALS Ceramics
Aluminum oxide powder (fine‑grained Al2O3) along with additives of titanium, magnesium, or chromium oxide, is mixed with a binder and processed into a cutting tool insert by powder metallurgy techniques. Because of this the inserts must be given a 5° to 7° negative rake to strengthen their cutting edge and be well supported by the toolholder.
Applications: high speed turning of cast iron and steel
Not recommended for heavy interrupted cuts (e.g. rough milling) due to low toughness
Al2O3 also widely used as an abrasive in grinding

19. CUTTING TOOL MATERIALS Synthetic Diamonds
Sintered polycrystalline diamond (SPD) - fabricated by sintering very fine‑grained diamond crystals under high temperatures and pressures into desired shape with little or no binder
Usually applied as coating (0.5 mm thick) on WC-Co insert
Applications: high speed machining of nonferrous metals and abrasive nonmetals such as fiberglass, graphite, and wood
Not for steel cutting

20. CUTTING TOOL MATERIALS Synthetic Diamonds
SPD (Sintered Polycrystalline Diamond) Tools are carbides with diamond inserts. They are restricted to simple geometries.

21. CUTTING TOOL MATERIALS Cubic Boron Nitride (CBN)
Next to diamond, cubic boron nitride (CBN) is hardest material known
Fabrication into cutting tool inserts same as SPD: coatings on WC‑Co inserts
Applications: machining steel and nickel‑based alloys
SPD and CBN tools are expensive

22. Properties of Cutting Tool Materials

23. Cutting Tool Classification
Single-Point Tools
Used for turning, boring, shaping, and planing
One dominant cutting edge
Point is usually rounded to form a nose radius
Turning uses single point tools
Multiple Cutting Edge Tools
Used for drilling, reaming, tapping, milling, broaching, and sawing
More than one cutting edge
Motion relative to work achieved by rotating
Drilling and milling use rotating multiple cutting edge tools

24. Cutting Tools
(b) a helical milling cutter, representative of tools with multiple cutting edges
(a) A single‑point tool showing rake face, flank, and tool point

25. Holding the Single-Point Cutting Tool
Three ways of holding and presenting the cutting edge for a single‑point tool: (a) solid tool, typical of HSS; (b) brazed insert, one way of holding a cemented carbide insert; and (c) mechanically clamped insert, used for cemented carbides, ceramics, and other very hard tool materials.

26. Common Insert Shapes
Common insert shapes: (a) round, (b) square, (c) rhombus with two 80 point angles, (d) hexagon with three 80 point angles, (e) triangle (equilateral), (f) rhombus with two 55 point angles, (g) rhombus with two 35 point angles. Also shown are typical features of the geometry.
A collection of metal cutting inserts made of various materials

27. Multiple Cutting Edge Tools
Twist Drills
Twist drills are by far the most common cutting tools for hole‑making and usually made of high speed steel
Standard geometry of a twist drill.
TWIST DRILL OPERATION
Rotation and feeding of drill bit result in relative motion between cutting edges and workpiece to form the chips
Cutting speed varies along cutting edges as a function of distance from axis of rotation
Relative velocity at drill point is zero, so no cutting takes place
A large thrust force is required to drive the drill forward into hole

28. DRILL BID (CUTTER) (matkap ucu)
Drill bid is a rotational cutter. It may have one are more cutting edges. As the drill advances into hole, produced chips must move out. Thus, drill bids have helical flutes (channels).
Drill bid is composed of two geometric parts; shank and fluted body (cutting part). Shank may be cylindrical (düz sap) or tapered (konik sap). For tapered shanks “Morse taper” (5% slope) is common.
Standard twist drill (spiral matkap) terms:
(shank-sap, body-gövde, margin-zırh, land-sırt, chisel edge- uc, web-çekirdek/öz, point angle-uç açısı, lip relief angle-boşluk açısı)

29. When Using Standard Twist Drill
Point Angle (uç açısı): Generally 118°, but may change with the material to be drilled (could be 90° for soft materials or 130° for hard materials)
Helix Angle (helis açısı): Produced by the factory. Operator may only select with drill bids with different helix angles. It’s generally 30°.
Cutting Speed (tangential speed of the drill (V--m/min)) = 3.14*Drill Diameter (D--mm)* Rotational Speed of the Drill (N—rev/min)/1000
Feed (ilerleme hızı): Depends on the tool and work materials. Generally mm/rev.
Hole Tolerances: All drill bids produces holes larger than their diameter. The amount of oversize is; Oversize = D (drill diameter---mm)
Hole surface quality: Drilling operation produces a rough surface. It should be improved by using reamers.

30. Twist Drill Operation - Problems
Chip removal
Flutes must provide sufficient clearance to allow chips to be extracted from bottom of hole during the cutting operation
Friction makes matters worse
Rubbing between outside diameter of drill bit and newly formed hole
Delivery of cutting fluid to drill point to reduce friction and heat is difficult because chips are flowing in opposite direction

31. Multiple Cutting Edge Tools MILLING CUTTERS

32. Multiple Cutting Edge Tools Milling Cutters
Principal types: Plain milling cutter Face milling cutter End milling cutter
Plain Milling Cutter
Face Milling Cutter
Teeth cut on side and periphery of the cutter
Used for peripheral or slab milling
Tool geometry elements of a four‑tooth face milling cutter: (a) side view and (b) bottom view.
Tool geometry elements of an 18‑tooth plain milling cutter

33. PLAIN MILLING CUTTER
Used for milling flat surfaces (plain or slab milling).
They are cylindrical or disk-shaped, have straight or helical teeth on the periphery.
Helical teeth are preferred over straight teeth due to reduced shock and chattering during cutting action.

34. FACE MILLING CUTTER

35. END MILLING CUTTER
Looks like a drill bit but designed for primary cutting with its peripheral teeth
Applications:
Face milling
Profile milling and pocketing
Cutting slots
Engraving
Surface contouring
Die sinking

36. Multiple Cutting Edge Tools IN MORE DETAIL MILLING CUTTERS
Arbor Milling Cutters (malafa çakıları): These are cylindrical cutters with a hole and they are mounted to a long arbor to these holes. The cutting tool cuts on the periphery of the cutter.
Shank Milling Cutters (saplı çakılar): Cutters have a cylindrical or tapered shank. They generally cut on the face.

37. Multiple Cutting Edge Tools IN MORE DETAIL MILLING CUTTERS
Face Milling Cutters (alın çakıları): They are used as shank cutters. They don’t have a shank but they have a hole. They are mounted on a short arbor.
End Milling Cutters (parmak freze): These are shank cutters having cylindrical or tapered shanks.

38. Multiple Cutting Edge Tools IN MORE DETAIL MILLING CUTTERS
G-T-Slot Milling Cutter
(T-kanal frezesi): They have a shank or they may be mounted on a short arbor. Used for making undercuts in a workpiece.
Slab Milling Cutter
(silindirik freze çakısı): These are cylindrical cutters mounted on a long arbor. They cut with their periphery. Teeth may be straight or helical.
Side Milling Cutters:They are also cylindrical cutters but their end faces are having cutting edges as well.

39. Multiple Cutting Edge Tools IN MORE DETAIL MILLING CUTTERS
Saw Cutters (testere freze): They are short cylindrical cutters (in discs shape). Thickness may be 0.8 to 5 mm.
Angle Cutters (açı frezesi): They produce certain angles in the workpiece. In geometry they are arbor cutters with their cutting edges on there periphery.
Form Cutters (biçim/form frezesi): There are various cutters for producing gear profiles or convex/concave curvatures

40. Cutting Fluids
Improvement in cutting action may be accomplished by using solids, liquids, emulsions, or gases in the cutting process.
Most cutting fluids are in liquid form because they may be directed on the tool at the proper place and are easily recirculated.
Solids that improve cutting ability include certain elements in the workpiece such as graphite in grey cast iron or lead in steel.
Liquids are principally in the form of water base (COOLANTS) or oil base solutions (LUBRICANTS) with certain additives in them to increase their effectiveness.
Gases include water vapor, carbon dioxide and compressed air.

41. Cutting Fluids 2. Reduce the temperature of the tool and work.
SO A PROPER CUTTING FLUID CAN PERFORM THE FOLLOWING FUNCTIONS:
1. Reduce friction between chip, tool, and workpiece.
2. Reduce the temperature of the tool and work.
3. Wash away chips.
4. Improve the surface finish.
5. Reduce the power required.
6. Increase the tool life.
7. Reduce possible corrosion on both work and machine.
8. Prevent or reduce welding the chip to the tool.

42. Cutting Fluid Functions
Cutting fluids can be classified according to function:
Coolants - designed to reduce effects of heat in machining
Lubricants - designed to reduce tool‑work friction
COOLANTS
Water used as base in coolant‑type cutting fluids
Most effective at high cutting speeds where heat generation and high temperatures are problems
Most effective on tool materials that are most susceptible to temperature failures (e.g., HSS)
LUBRICANTS
Usually oil‑based fluids
Most effective at lower cutting speeds
Also reduce temperature in the operation

43. Dry Machining No cutting fluid is used
Avoids problems of cutting fluid contamination, disposal, and filtration
Problems with dry machining:
Overheating of tool
Operating at lower cutting speeds and production rates to prolong tool life
Absence of chip removal benefits of cutting fluids in grinding and milling