Ch 19 Cutting Tool Technology

Of the following cutting conditions, which one has the greatest effect on tool wear: 1.cutting speed, 2.depth of cut, 3.feed

1.cutting speed

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

1. Crater wear - The top rake face 2. Flank wear - The flank

Identify the mechanisms by which cutting tools wear during machining.

1. Abrasion: hard particles in the work material removing small portions of the tool. Occurs in both flank wear and crater wear. 2. Adhesion: high pressure and temperature, adhesion or welding occur. Present between the chip and the rake face of the tool. 3. Diffusion: occurs at the tool-chip boundary, causing the tool surface to become depleted of the atoms responsible for this hardness. Tool surface becomes more susceptible to abrasion and adhesion. 4. Chemical reactions: high temperatures and clean surfaces at the tool-chip interface and high speeds can result in chemical reactions, in particular, oxidation, on the rake face of the tool. 5. Plastic deformation: high temperature cause the edge to deform plastically, making it more vulnerable to abrasion of the tool surface.

What are the two principal aspects of cutting tool technology ?

1. Tool material 2. Tool geometry

Which of the following are the two main functions of a cutting fluid in machining (two best answers): 1.improve surface finish on the workpiece, 2.reduce forces and power, 3.reduce friction at the tool-chip interface, 4.remove heat from the process, and 5.wash away chips?

3.reduce friction at the tool-chip interface 4.remove heat from the process

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

1. Complete failure of cutting edge 2. Visual inspection of flank wear (or crater wear) by the machine operator 3. Fingernail test across cutting edge 4. Changes in sound emitted from operation 5. Chips become ribbony, strongly, and difficult to dispose of 6. Degradation of surface finish 7. Increased power 8. Workpiece count 9. Cumulative cutting time

Name the two main categories of cutting fluid according to function.

1. Coolants - reduce the effect of heat in the machining operation 2. Lubricants - reduce friction at the tool-chip and tool-work interfaces.

Dry machining is being considered by machine shops because of certain problems inherent in the use of cutting fluids. What are those problems associated with the use of cutting fluids?

1. Cutting fluid contamination 2. Disposal 3. Filtration

Name the three modes of tool failure in machining.

1. Fracture failure: Cutting force becomes excessive, leading to brittle fracture. Premature failure. 2. Temperature failure: Cutting temperature is too high for the tool material. Premature failure. 3. Gradual wear: Gradual wearing of the cutting tool. This is preferred of the three because it leads to the longest possible use of the cutting tool.

What are some of the new problems introduced by machining dry?

1. Overheating of the tool 2. Operating at lower cutting speeds and production rates to prolong tool life 3. Absence of chip removal benefits in grinding and milling

Identify three desirable properties of a cutting tool material.

1. Toughness - to avoid fracture failure 2. Hot hardness - ability to retain hardness at high temperatures 3. Wear resistance - hardness is the most important property to resist abrasive wear

Which of the following is not a common ingredient in cemented carbide cutting tools (two best answers): 1.A12O3, 2.Co, 3.CrC, 4.TiC, 5.WC

1.A12O3 3.CrC

Cast cobalt alloys typically contain which of the following main ingredients (three best answers): 1.aluminium, 2.cobalt, 3.chromium, 4.iron, 5.nickel, 6.steel, 7.tungsten

2.cobalt 3.chromium 7.tungsten

In addition to cutting speed, what other cutting variables are included in the expanded version of the Taylor tool life equation?

Feed, depth of cut, hardness, (p, m, q) exponents for whose values are experimentally determined for the conditions of the operation, K = a constant analogous to C, f(ref), d(ref) and H(ref) = reference values for feed, depth of cut and hardness. Tool life, n.