Lecture 5: Machining

Question 1

Machining is

Answer 1

is the removal of the material or modification of
surfaces without changing the structure of the material.

Question 2

Machining is done:

Answer 2

• Without changing the structure of the material since it does not heat up.
• By producing chips for removing material using
  various tools.

Question 3

Machining
has 5 characteristics:

Answer 3

b. Allows us to make complex shape
c. Tool doesn’t have information about product geometry
d. Good dimensional accuracy – depends on the knowledge of the tool operator which translates from the tool to
the material
e. Good surface finish
f. Advantage – we use generic tools, not special machines ➔ we don’t have to order machines, dies ➔ no long
initial period

Question 4

3 Properties

Answer 4

i. cutting
* Rake angle – α
* Clearance angle
ii. shearing
* Shearing angle – Φ
iii. Depth - t0
iv. Important: Rake angle (α) + Tool angle (β) + Relief angle (γ) = 90°

Question 5

Rake angle =

Answer 5

Angle of the cutting tool relative to the work. It
is mentioned with a

Question 6

Relief / clearance angle =

Answer 6

Angle between the horizontal
surface and the cutting tool. It is mentioned with y

Question 7

Tool angle =

Answer 7

the angle of the tip of the tool, which is β

Question 8

Shearing angle =

Answer 8

The angle made by the shear plane with the direction of tool travel. It is
mentioned with ф

Question 9

What determines (4) the name of a machining process?

Answer 9

1. If the workpiece rotates: turning, cutting off, or hole making.
2. If the workpiece slides: scraping.
3. If the tool rotates: slab milling or end milling.
4. If the tool slides: scraping or broaching

Question 10

What are the key operating factors in machining processes? 6

Answer 10

Depth: Tool penetration into the workpiece.
Speed: Rotation of the workpiece.
Feed: Rate of material removal along the length of the workpiece.
Tool angle: Adjustment affecting cutting forces.
Type of chips produced.
Tool wear, a significant concern in machining.

Question 11

How are fluids used in machining? 5 ways

Answer 11

Cooling.
Reducing friction and wear.
Flushing away chips.
Protecting against corrosion.
Types include oils, emulsions, semi-synthetics, and synthetics.

Question 12

describe each type of fluid:oils, emulsions, semi-synthetics, and synthetics.

Answer 12

Oils: For low temperatures and low working speed, oils can be used. High speed will result in a big risk of burning the oil.
- Emulsions: Used for high speed and high temperatures. This is a mix of water and oil
- Semi-synthetics: Most of the time little oil in water.

Question 13

How does temperature affect machining?

Answer 13

Most heat is removed by the chip, keeping the workpiece relatively cool.
Elevated temperatures can cause tool wear and affect product geometry.
Synthetics: Chemicals and additives in water

Question 14

What factors influence cutting forces in machining?

Answer 14

Workpiece material strength.
Rake angle of the tool.
Feed rate.
Depth of cut.

Question 15

Name 6 important characteristics of cutting tools.

Answer 15

Hot hardness.
Toughness and impact strength.
Thermal shock resistance.
Wear resistance.
Chemical stability and inertness.
ISO classification.

Question 16

different tools have different cutting speeds. The 7 materials in
order of speed are:

Answer 16

Tool steel, High speed steels, Hard metal, Coated
Carbides, Ceramics, Cubic Boron Nitride, Diamond.

Question 17

Dependent on the tool
characteristics, the life time of the tool will be changed:

Answer 17

• The constant (C) increases with decreasing depth of cut.
• The constant (C) increases with a decrease in feed.
• The constant (C) is affected by all factors around the machine

Question 18

What does “turning” refer to in machining?

Answer 18

Turning involves a rotating workpiece and a stationary tool.
The resulting product is rotationally symmetrical.

Question 19

What are some characteristics of turning?

Answer 19

Product geometry: Rotational symmetrical(straight, conical, curved/grooved).
Materials: All kinds.
Advantage: Use of generic tools.no lead
time
Disadvantage: Low production rate.

Question 20

How is chip control managed in turning?

Answer 20

Chip breakers are used to prevent large, damaging chips from forming during the continuous cutting process.

Question 21

What types of products can be made using turning?

Answer 21

Housing bases.
Inner bearing races.
Tube reducers.
Screw threads.

Question 22

Surface finish
i. Explicit factors:
ii. Noise factors:

Answer 22

– feed rate (f), tool geometry (R)
– build up edge, vibrations

Question 23

What 2 types of tools are used in turning?

Answer 23

Inserts: Various shapes, with sharper tools producing better finishes.
Guided lathe: Large machines, often computer-controlled.

Question 24

What are 3 requirements for turning?

Answer 24

Machine size should accommodate product dimensions.
Tool should meet speed and cost requirements.
Product geometry is typically rotational symmetrical.

Question 25

What is boring in the context of machining?

Answer 25

Boring enlarges holes with minimal force, often using large machines with rotating tables.

Question 26

What are some common machining operations in turning?

Answer 26

Facing: Working on the front side of a rotating product.
Straight turning: Reducing the diameter of the product.

Question 27

give 2 reasons why are simulations often used in turning?

Answer 27

To optimize logistics and speed.
To ensure that tools can reach every part of the product.

Question 28

What distinguishes boring from turning?

Answer 28

Boring enlarges internal diameters, while turning cuts external diameters.

Question 29

What is drilling?

Answer 29

Drilling involves making screw threads inside a hole.

Question 30

What 2 factors determine the shape of the hole in drilling?

Answer 30

Tool geometry immediately determines the shape.
Maximum hole depth is related to the tool diameter

Question 31

What is torque in drilling?

Answer 31

Torque refers to the rotational force between the drill string and the formation.

Question 32

What is feed force in drilling?

Answer 32

Feed force is the force that pushes the tool against the material.

Question 33

Tool wear – determined by

Answer 33

the remaining useful length of
the drill after sharpening

Question 34

when making holes in a thin sheet of metal

Answer 34

the metal has to be stabilized, else it will start spinning
around the drill in the air

Question 35

Chip angle – varies

Answer 35

over the diameter of the drill ➔ positive (outside diameter) and negative (near the core)
chip angles

Question 36

What is milling?

Answer 36

Milling involves a rotating tool moving with respect to the workpiece.

Question 37

What are the parameters involved in milling?

Answer 37

Rotational speed, feed, depth of cut.

Question 38

What are the two strategies in milling?

Answer 38

Conventional milling (up milling).
Climb milling (down milling).

Question 39

What is grinding?

Answer 39

Grinding uses a disc with many undefined cutting edges.

Question 40

What factors affect grinding temperature?

Answer 40

Heat drain, high temperatures, and cooling methods.

Question 41

What is electrical-discharge machining (EDM)?

Answer 41

EDM involves using electrical discharge to melt or evaporate material under a dielectric fluid.

Question 42

What is electro-chemical machining (ECM)?

Answer 42

ECM shapes workpieces using electrolysis in a saline electrolyte.

Question 43

What is electrolyte in ECM?

Answer 43

Electrolyte is a salty saline fluid that conducts electricity.