Machining Fundamentals

Question 1

What is machining?

Answer 1

The process of removing material from a base piece to form a part

Question 2

What deformation does the cutting action form?

Answer 2

Shear deformation

Question 3

Which materials are usually machined

Answer 3

Metals

Question 4

What are the main upsides to machining?

Answer 4

Variety of shapes and dimensional accuracy

Question 5

What are the main downsides to machining?

Answer 5

Wastes material, time consuming

Question 6

When is machining performed?

Answer 6

Usually after the forming processes

Question 7

What are the 3 most common machining types?

Answer 7

Turning, drilling, and milling

Question 8

What is turning?

Answer 8

A cutting tool moves parallel to the work axis while the work piece rotates on said axis

Question 9

What is the speed of a turning operation?

Answer 9

Surface speed of work piece

Question 10

What is drilling?

Answer 10

The tool (drill bit) rotates while moving towards a stationary work piece

Question 11

What is the speed of a drilling operation?

Answer 11

Speed of the tool rotation

Question 12

Which operations have feed motions that are done by the tool?

Answer 12

Drilling and turning

Question 13

When the workpiece is fed towards a stationary rolling cutter, what is the process called?

Answer 13

Milling

Question 14

What is a single point cutting tool?

Answer 14

There is one dominant cutting edge, and the point is rounded to form a nose radius

Question 15

What is a multiple cutting edge tool?

Answer 15

There are more than one cutting edge, and the motion is achieved by the tool rotating

Question 16

What is the rake face?

Answer 16

The part of the cutting tool that directs the chip flow

Question 17

What is the flank?

Answer 17

The part of the cutting tool lifted an angle from the new surface of the work part to provide relief

Question 18

How is material removal rate computed?

Answer 18

Cutting speed * feed * cut depth [length/time * length * length]

Question 19

What is roughing?

Answer 19

The process of removing large amounts of material from the starting work part, getting close to the desired shape

Question 20

What is finishing?

Answer 20

Completes part geometry by cutting to required tolerances and finish

Question 21

What is the rake angle?

Answer 21

The angle that the tool makes with the perpendicular axis of the workpiece

Question 22

What is the shear angle?

Answer 22

When the chip is formed, the angle of the remaining workpiece relative to the projected new surface

Question 23

What is the shear strain

Answer 23

The measure of angular deformation of a material when subjected to a shear force

Question 24

What is the primary shear zone

Answer 24

Where deformation of the material takes place

Question 25

What is the secondary shear zone?

Answer 25

The area along the rake face, where friction is happening

Question 26

What determines the chip type of a cutting process?

Answer 26

Material properties, cutting condition,

Question 27

What causes continuous chip?

Answer 27

Ductile material when the tool has a sharp cutting edge, high cutting speeds or rake angle , small feed and depth of cut

Question 28

What properties does the resultant machined surface have?

Answer 28

Good surface finish

Question 29

What is the issue with continuous chip?

Answer 29

The chip tangles and can get caught by the tool

Question 30

What is a chip breaker?

Answer 30

An addition to then rake face of the tool that forces the chip to break

Question 31

What is a built up edge chip?

Answer 31

Continuous chip where parts of the metal begin to adhere to the edge of the cutting tool

Question 32

What causes BUE?

Answer 32

Low/medium cutting speeds; local high temperatures and extreme pressure in the cut zone

Question 33

How to reduce BUE?

Answer 33

Reduce depth of cut, use a positive rake angle, apply coolant, or increase cutting speed

Question 34

What is a serrated chip?

Answer 34

The chip is jagged away from the rake face

Question 35

What causes serrated chips?

Answer 35

Difficult materials, high cutting speeds

Question 36

What is a discontinuous chip?

Answer 36

Chip cannot stay continuous, and breaks on formation

Question 37

What causes discontinuous chips?

Answer 37

Brittle materials, low cutting speed, large feed and depth of cut, low rake angle, lack of coolant.

Question 38

What is the transition of chips as the velocity is increased?

Answer 38

Discontinuous, to sliding, to sticking

Question 39

Where does the friction force occur?

Answer 39

Parallel to the rake face, going towards the work piece.

Question 40

Where does the normal force occur?

Answer 40

Perpendicular to the friction, pointing towards the chip

Question 41

Where does the shear force occur?

Answer 41

Along the raised part of the shear angle

Question 42

Where does the normal shear force occur?

Answer 42

Perpendicular to the shear force, pointing at the chip

Question 43

Which forces involved in cutting are able to be measured?

Answer 43

Cutting and thrust force

Question 44

Where does cutting force occur?

Answer 44

Along the projected new surface, pointing towards the tool

Question 45

Where does the thrust force occur?

Answer 45

Perpendicular the the new surface

Question 46

What is the Merchant Circle Diagram?

Answer 46

Visual representation of all forces acting upon a workpiece

Question 47

What does the Merchant's Equation describe?

Answer 47

The relationship between the shear, rake, and friction angle

Question 48

What does the merchant's equation imply?

Answer 48

- Increase in rake angle causes a larger shear angle - decrease in friction angle causes larger shear angle - Turning can be reduced to orthogonal cutting if the feed is small relative to cut depth

Question 49

How is the cutting power of a machining operation found?

Answer 49

The product of the cutting force and cutting speed

Question 50

What is the factor of conversion from ft*lbf/min to HP

Answer 50

Dividing by 33000

Question 51

How is the gross power found?

Answer 51

Dividing the cutting force by the mechanical efficiency of a tool