Chapter 22

Question 1

Carbide tools

Answer 1

Coated, exclusively by the chemical vapor deposition process (cc’d)

Question 2

Things that influence tool material decisions

Answer 2

Work material characteristics (hardness), part characteristics (geometry, accuracy, finish), machine tool characteristics (work holders, sped and feed ranges), support systems (sensors, controls, chip removal).

Question 3

Three main sources of heat

Answer 3

1) the shear front itself 2) the tool/chip interface contact region 3) the flank of the tool where the produced workpiece surface rubs the tool.

Question 4

Rate of wear?

Answer 4

Directly related to temperature

Question 5

Hot hardness

Answer 5

Tools that do not lose hardness at the high temperatures associated with high speeds

Question 6

Common toughness tests?

Answer 6

Izod and Charpy impact tests.

Question 7

Toughness

Answer 7

The ability to take impacts during interrupted cutting

Question 8

Impact strength

Answer 8

It’s ability to withstand impacts, and not wear the tool down. This saves money on tools.

Question 9

Cutting speed and feed are

Answer 9

Limited br the capability of the tools material

Question 10

Physical vapor deposition

Answer 10

15 to 20 percent of all took steels are coated by this process

Question 11

Cermets

Answer 11

New ceramic materials

Question 12

Tool steels

Answer 12

Carbon steels and low medium alloy steels. Important properties are hardness hot hardness and toughness

Question 13

High speed steels

Answer 13

First introduced by f w Taylor and Mandel white in 1900. Retains its cutting ability at high temperatures. Can opérateurs at about double or triple cutting speeds.

Question 14

High speed steels are used in

Answer 14

Drills and many milling cutters and single point tools

Question 15

Strengths of high speed steels?

Answer 15

Great toughness, easily fabricated, and best for sever applications where complex tool geometry is needed (gear cutters, tap, drills, framers, and dies)

Question 16

Hss coated with TiN includes

Answer 16

Readers, taps, chasers, spade drill blades, broaches, bandsaw, and circular band saws.

Question 17

Pvd processing

Answer 17

Tools are subjected to a vigorous cleaning process as a pretreatment.

Question 18

Main advantage of tin coated hss tooling

Answer 18

Reduced tool wear. Less stock removal. Longer tool life. Low coefficient of friction

Question 19

Carbide cutting tool I serfs are traditionally dived into two primary groups

Answer 19

Straight tungsten grades, use for machining cast irons, nonmetallic surfaces. Grades containing major amounts of titanium, tantalum, use for machining ferritin workpieces.

Question 20

Carbides

Answer 20

Nonferrous alloys, called sintered carbides, because they are manufacture by powder metallurgy techniques.

Question 21

Cemented carbide tools are available in insert form in many shapes such as:

Answer 21

Squares triangles diamonds and rounds. Mechanical clamping attached the insert.

Question 22

Chip groove

Answer 22

Has a positive take angle at the tool too, may be used to reduce d cutting forces without reducing the overall strength of the insert significantly.

Question 23

Purpose of multiple coatings?

Answer 23

Prolonged tool life better metallurgical bond.

Question 24

Two most effective coasting processes:

Answer 24

Chemical vapor deposition and physical vapor deposition of titanium nitride and titanium carbide.

Question 25

Chemical vapor deposition:

Answer 25

Clean tools are heated until they reach the coating temperature, the coating cycle is initiated by the introduction of gages into the reactor.

Question 26

Forming titanium nitride for coating

Answer 26

Nitrogen hydrogen gas mixture is substituted for methane

Question 27

Pvd

Answer 27

Coated by condensation of a metal vapor. The vapor is formed by a source material called the charge, it is heated to temps less than 1000 C.

Question 28

Pvd process features

Answer 28

1 coating takes place inside a vacuum chamber, with the workpiece heated. 2 before coating, all parts are given a final cleaning inside the chamber to remove oxides and improve coating adhesion. 3 the coating temperature is relatively low for cutting tools. 4. The metal source is vaporize in an inert gas atmosphere. 5. These are ion assisted deposition processes.

Question 29

CVD over PVD

Answer 29

CVD is done at higher temperatures, so the coating are superior. The application can only be used to loosely tolerances tools.

Question 30

PVD over CVD

Answer 30

Can be used for all high speed steels, and carbide tools. Fine blanking punches. I

Question 31

Sources of tool life variability

Answer 31

1) variation in work hardness 2 variability in cutting tool materials, geometry, and preparation. 3 vibrations in machine tool 4 changing surface characteristics of workpieces.

Question 32

Criteria that defines tool death

Answer 32

When surface finish deteriorates, when the dimension is out of tolerance, power consumption increases to a limit, chip discoloration happens, and cutting time.

Question 33

Other ways to express tool life

Answer 33

Volume of metal removed, number of pieces machined, number of holes drilled.

Question 34

Machinability

Answer 34

Defined by the ease of difficulty with which the metal can be machined.

Question 35

Machinability

Answer 35

Defined by the relative cutting speed for a given tool life when cutting some material.

Question 36

Cutting speed

Answer 36

Measured by the maximum speed at which a tool can provide satisfactory performance.

Question 37

Other definitions of machinability

Answer 37

The ease of removal of Chios, the quality of the surface finish, the dimensional stability, or cost to remove a given volume of metal.

Question 38

Reconditioning cutting tools

Answer 38

1 resharpen to original tool geometry specifications. 2 grind cutting edges and surfaces to a fine finish. 3 remove all burrs in resharpened cutting edges. If a tool with a burr is coated, the uncleared surface will be exposed to wear. 4 avoid resharpening practices that overheat and burn of melt the tool surfaces.

Question 39

Cutting fluids

Answer 39

Fredrick w Taylor demonstrated that cutting fluids increase cutting abilities. Cutting fluids act as a coolant and a lubricant. The reduction in temperature aids in retaining the hardness of the tool and it’s cutting life.

Question 40

Cutting fluids should be

Answer 40

Stable in use and storage, non corrosive, and nontoxic.