Theory of Metal Machining Review Questions

Question 1

What are the three basic categories of material removal processes?

Answer 1

• Conventional Machining
• Abrasive Processes
• Nontraditional processes

Question 2

What distinguishes machining from other manufacturing processes?

Answer 2

Material is removed from the work part so that the remaining material is the desired part geometry

Question 3

Identify some of the reasons why machining is commercially and technologically important

Answer 3

• Variety of work materials
• Variety of part shapes and geometric features
• dimensional accuracy
• good surface finish

Question 4

Name the three most common machining processes.

Answer 4

• turning
• drilling
• milling

Question 5

What are the two basic categories of cutting tools in machining? Give two examples of machining operations that use each of the tooling types.

Answer 5

• Single-Point Tool
  
  • Turning
  • Boring
• Multiple-Cutting Edge Tool
  
  • Milling
  • Drilling

Question 6

What are the parameters of a machining operation that are included within the scope of cutting consitions?

Answer 6

• cutting speed
• feed
• depth of cut

Question 7

Explain the difference between roughing and finishing operations in machining.

Answer 7

Roughing

Used to remove a large amount of material from the starting workpart as rapidly as possible, in order to create a shape close to the desired form, but leaving some material on the piece for finishing

Finishing

Used to complete the part and achieve the final dimensions, tolerances, and surface finish

Question 8

What is a machine tool?

Answer 8

Used to hold the workpart, position the tool relative to the work, and provide power for the machining process at the speed, feed, and depth of cut that have been set

Question 9

What is an orthogonal cutting operation?

Answer 9

Uses a wedge-shape tool in which the cutting edge is perpendicular to the direction of cutting speed motion into the work piece

Question 10

Why is the orthogonal cutting model useful in the analysis of metal machining?

Answer 10

Simplifies the rather complex 3-Dimensional machining situation to 2-dimensions

The tooling in orthogonal model has only 2 parameters which is a simpler geometry than a single point tool

Question 11

Name and briefly describe the four types of chips that occur in metal cutting.

Answer 11

• Discontinous Chip
  
  • relatively brittle materials machined at low cutting speed
  • Separate segments, some loosely atached at times
• Continous Chip
  
  • ductile work material cut at high speed and small feeds/depth
  • Long continous chips are formed, with good surface finish resulting
• Continous Chip with Built-up Edge
  
  • ductile materials at low-medium cutting speeds
  • portions of work material adhere to rake faces of tool near cutting edge
• Serrated Chip
  
  • semicontinous in the sense that they possess a sawtooth appearance that is produced by a cyclical chip formaton alternating from high shear strain to low shear strain
  • Associated with difficult to machine metals

Question 12

Identify the four forces that act upon the chip in the orthogonal metal-cutting model but cannot be measured directly in an operation.

Answer 12

• friction force
• normal force to friction
• shear force
• normal force to shear

Question 13

Identify the two forces that can be measured in the orthogonal metal-cutting model.

Answer 13

• cutting force
• thrust force

Question 14

What is the relationship between the coefficient of friction and the friction angle in the orthogonal cutting model?

Answer 14

Tangent relationship

Question 15

Describe in words what the Merchant equation tells us.

Answer 15

Defines general relationship between rake angle, tool-chip friction, and shear plane angle

Shear plane can be increased through:

1. icnreased rake angle
2. decrease friction angle between tool and chip

Question 16

How is power required in a cutting operation related to the cutting force?

Answer 16

The power required in a cutting operation is equal to the cutting force multiplied by the cutting speed

Question 17

What is the specific energy in metal machining>

Answer 17

The amount of energy required to remove a unit volume of the work material

Question 18

What does the term size effect mean in metal cutting?

Answer 18

The size effect refers to the fact that the specific energy increases as the cross-sectional area of the chip decreases

Question 19

What is a tool-chip thermocouple?

Answer 19

Comprised of the tool and chip as the two dissimilar metals forming the thermocouple junctions; as the tool-chip interface heats up during cutting, a small voltage is emitted from the junction that can be measured to indicate cutting temperature