Cutting Tool Technology
Identify the alternative ways by which a cutting tool is held in place during machining
There are three principal 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, cermets, ceramics, SPD, and CBN.
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/or TaC in addition to WC-Co.
. (SI units) In the tool wear plots of Figure 22.4, complete failure of the cutting tool is indicated by the end of each wear curve. Using complete failure as the criterion of tool life instead of 0.50 mm flank wear, the resulting data are: (1) v = 160 m/min, T = 5.75 min; (2) v = 130 m/min, T = 14.25 min; and (3) v = 100 m/min, T = 47 min. Determine the parameters n and C in the Taylor tool life equation for this data.
Let us use the two extreme data points to calculate the values of n and C, then check the resulting equation against the middle data point. (1) 160(5.75)n = C and (3) 100(47)n = C 160(5.75)n = 100(47)n ln 160 + n ln 5.75 = ln 100 + n ln 47 5.0752 + 1.7492 n = 4.6052 + 3.8501 n 0.4700 = 2.1009 n n = 0.224 (1) C = 160(5.75)0.224 = 236.7 (3) C = 100(47)0.224 = 236.9 use average: C = 236.8 m/min
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, and (4) 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 a one-minute tool life. C is the speed-axis intercept on the log-log plot of the tool life data.
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 three desirable properties of a cutting-tool material.
Three desirable properties 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 tool 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. Portions of flank wear are often identified separately as notch wear, corresponding to the surface of the work; and nose radius wear, corresponding to the tool point.
