IN THE NAME OF ALLAH, THE MOST MERCIFUL, THE MOST BENEFICIENT. 1

2 Engr. Abid Hussain Lecturer MED U.E.T. Taxila

 First cutting-tool inserts on market in 1956  Inconsistent: improper use and lack of knowledge  Uniformity and quality greatly improved  Widely accepted by industry  Used in machining of hard ferrous materials and cast iron  Gain: lower costs, increased productivity  Operate 3 to 4 times speed of carbide toolbits 3

 Most economical  Especially if tool shape must be altered from standard shape  Bonded to steel shank with epoxy glue  Eliminates strains caused by clamping inserts in mechanical holders 4

 Retain their strength and hardness at high machining temperatures [in excess of 2000°F]  Withstand abrasion of sand inclusions  Better surface finish  Heat-treated materials as hard as Rockwell c 66 can be readily machined 5

 Brittle and therefore tend to chip easily  Satisfactory for interrupted cuts only under ideal conditions  Initial cost of ceramics higher than carbides.  Require more rigid machine than is necessary for other cutting tools  Considerably more power and higher cutting speeds required for ceramics to cut efficiently 6

 Material to be machined  Operation performed  Condition of machine  Rigidity of work setup  Rigidity of toolholding device 7

 Use highest cutting speed possible that gives reasonable tool life  Two to ten times higher than other cutting tools  Less heat generated due to lower coefficient of friction between chip, work, and tool surface  Most of heat generated escapes with chip 8

 Great wear resistance (permit higher cutting speeds than carbide tools)  Edge buildup and cratering minimal  High hot-hardness qualities  Greater than carbide but less than ceramic  Lower thermal conductivity than carbide because heat goes into chip  Fracture toughness greater for ceramic but less for carbide tools 9

 Two distinct types  Polycrystalline cubic boron nitride  Polycrystalline diamond  Manufacture of blanks basically same  Layer of polycrystalline diamond or cubic boron nitride (.020 in. thick) fused on cemented- carbide substrate by high temperature (3275ºF), high pressure (1 million psi) 10

 Created from substrate composed of tiny grains of tungsten carbide cemented tightly together  Cobalt binder  High-heat, high-pressure conditions  Cobalt liquefies, flows up and sweeps around diamond or cubic boron nitride abrasive  Serves as catalyst that promotes intergrowth 11

 Structure of cubic boron nitride feature nondirectional, consistent properties  Resist chipping and cracking  Provide uniform hardness  Abrasion resistance in all directions  Qualities built into turning and milling butting-tool blanks and inserts  Can operate at higher cutting speeds, and take deeper cuts 12

 Hardness  Impact resistance, high strength, hardness in all directions (random orientation of tiny CBN crystals)  Highest Hot Hardness of all tools  Abrasion Resistance  Maintain sharp cutting edges much longer  Second only to Diamond 13

 Compressive Strength  Maximum stress in compression material will take before ruptures  Thermal Conductivity  Allow greater heat dissipation or transfer 14

 High Material-Removal Rates  Cutting speeds (250 to 900 ft/min) and feed rates (.010 to.020 in.) result in removal rates three time carbide tools with less tool wear  Cutting Hard, Tough Materials  Capable of machining all ferrous materials with Rockwell C hardness of 45 and above  Also used to machine cobalt-base and nickel- base high temperature alloys (Rockwell c 35) 15

 Polycrystalline diamond (PCD) layer fused to cemented-carbide substrate .020 in. thick  Highly efficient cutting tool  Increased production when machining abrasive nonmetallic, nonferrous materials 16

 Catalyst-bonded PCD available in three microstructure series  Coarse PCD blanks  Medium-fine PCD blanks  Fine PCD blanks  Basic difference between types is size of diamond particle used to manufacture blank 17

 Composite materials found in base provide mechanical properties  High thermal conductivity and low coefficient of thermal expansion  Diamond layer  Hardness, abrasion resistance, compressive strength, and thermal conductivity  Compressive strength highest of any tool  Thermal conductivity highest of any tool 18

Offset their higher initial cost 1. Long tool life 2. Cuts tough, abrasive material 3. High quality parts 4. Fine surface finishes 5. Reduced machine downtime 6. Increased productivity 19

1. Nonferrous metals  Typically soft but have hard particles dispersed  Silicon-aluminum alloys  Copper alloys 2. Tungsten carbide 3. Advanced composites 4. Ceramics 5. Wood composites 20

1. Carbon Solubility Potential 2. Their higher initial cost 21

 Early 1980s brought new process of chemical vapor deposition (CVD)  Produce diamond coating few microns thick  Process  Elemental hydrogen dissolved in hydrocarbon gas around 1330º  Mixture contacts cooler metal, carbon precipitates in pure crystalline form and coats metal with diamond film (slow 1-5 microns/hr) 22