Chapter 22 Cutting Tool Technology

What are some of the tool life criteria used in production machining operations?

As identified in the text, tool life criteria used in production include (1) complete failure of the tool, (2) visual observation of flank or crater crater wear by the machine operator, (3) changes in the sound emitted by the tool, (4) degradation of surface finish, (5) power increase, (6) workpiece count, and (7) length of cutting time for the tool.

Why are ceramic cutting tools generally designed with negative rake angles?

Ceramics possess low shear and tensile strength but good compressive strength. During cutting, this combination of properties is best exploited by giving the tool a negative rake angle to load the tool in compression.

What is the difference in ingredients between steel cutting grades and nonsteel-cutting grades of cemented carbides?

In general, non-steel cutting grades contain only WC and Co. Steel cutting grades contain TiC and/orTaC in addition to WC-Co.

Why can diamond cutting tools not be used to machine steel and other ferrous metals?

Machining steel and other ferrous metals with SPD tools is not practical because of the chemical affinity that exists between these metals and carbon, because diamond is carbon.

What is the chemical formula of the ceramic material used in almost all ceramic cutting tools?

The chemical formula is Al2O3

Identify some of the common compounds that form the thin coatings on the surface of coated carbide inserts.

The common coatings are: TiN, TiC, and AL2O3

Identify the mechanisms by which cutting tools wear during machining.

The important tool wear mechanisms are (1) abrasion, (2) adhesion, (3) diffusion, (4) chemical reactions, and (5) plastic deformation of the cutting edge.

What is the physical interpretation of the parameter C in the Taylor tool life equation?

The parameter C is the cutting speed corresponding to one-minute tool life. C is the speed-axis intercept on the log-log plot of the tool life data.

What is the physical interpretation of the parameter n in the Taylor tool life equation?

The parameter n is the slope of the log-log plot of the tool life data. It indicates how strongly tool life is affected by cutting speed.

Name the seven elements of tool geometry for a single-point cutting tool.

The seven elements of single-point tool geometry are (1) back rake angle, (2) side rake angle, (3) end relief angle, (4) side relief angle, (5) end cutting edge angle, (6) side cutting edge angle, and (7) nose radius.

Name the three modes of tool failure in machining.

The three tool failure modes are (1) fracture failure, (2) temperature failure, and (3) gradual wear.

What are the two principal aspects of cutting-tool technology?

The two principal aspects of cutting tool technology are (1) tool material and (2) tool geometry.

Identify the three alternative ways of holding and presenting a cutting edge for a single-point cutting tool during machining.

There are three principle ways: (1) solid shank, in which the cutting edge is an integral part of the tool shank, an example being high speed steel tooling; (2) brazed inserts, used for some cemented carbides; and (3) mechanically clamped inserts, used for most hard tool materials including cemented carbides, coated carbides, cerments, ceramics, SPD, and CBN.

Identify three desirable properties of a cutting-tool material

Three desirable propertied are (1) toughness to resist fracture failure, (2) hot hardness to resist temperature failure, and (3) wear resistance to prolong the life of the tool during gradual wear.

What are the two principal locations on a cutting where tool wear occurs?

Wear occurs on the top face of the cutting tool as crater wear and on the side or flank of the tool, called flank wear.