Cutting Tool Material/Fluid

Question 1

Cutting tool characteristics

Answer 1

• able to maintain hardness, strength and wear resistance at elevated temperatures
• toughness
• thermal shock resistance
• wear resistance
• chemical resistance

Question 2

Tool material category

Answer 2

High spd steel
Cast cobalt alloy
Carbides
Ceramics
Cubic boron nitrides
Diamond

Question 3

High speed steel (material)

Answer 3

Pros - good wear resistance, inexpensive, high toughness and fracture resistance
Best for
- high + rake angle
- interrupted cut
- machine subj to vibration and chatter

How to improve:
- coating
-surface treatment
- steam treatment at elevated temp

Question 4

Cast-cobalt alloys (material)

Answer 4

Pros - high hardness, good wear resistance, can maintain hardness at high temp
Cons - sensitive to impact

Can be stellite tool - simple shapes use for deep continuous roughing cut at high feeds (2x HSS)

Question 5

Carbides (material)

Answer 5

Pros - hardness over wide range if temp, high elastic modulus and thermal conductivity, low thermal expansion.

Tungsten carbide - tungsten + cobalt. Cobalt increase = strength, hardness and wear resistance decrease = toughness increase

Titanium carbide - higher wear resistance but less tough.

Question 6

Inserts

Answer 6

Cutting tool with several cutting points, square have 8. Standardized so interchangeable

Question 7

Insert properties

Answer 7

Shape affect strength, bigger angle = higher strenghts.
Produced with negative land

Question 8

Carbides weakness and solution

Answer 8

Bad at light feed (concentrated force, chipping) and low cutting spd (cold welding).

Use cutting fluid

Question 9

Coated tool

Answer 9

Pros - low friction and high resistance to cracks and wear. Allow high cutting spd. Reduce production cost and operations

Coated tool have 10x life span

Question 10

Coated tools material characteristics

Answer 10

Insert by:
Chemical or physical vapor deposition

Characteristics:
1. High hardness at elevated temp
2. Chemical stability/inert to workpiece material
3. Good bonding to prevent flaking
4. Little or no porosity

Question 11

Example of coating

Answer 11

Titanium nitride
Titanium carbide
Ceramic
Diamond
Multiphase

Question 12

Titanium nitride (coating)

Answer 12

Pros - low friction, hardness, resistance to high temp, good adhesion. Low flank wear. Best at high cutting spd

Cons - bad at low spd, chip adhesion

Question 13

Titanium carbide (coating)

Answer 13

High flank wear resistance

Question 14

Ceramic coating

Answer 14

Pros- Chemically inert, low thermal conduct, resist high temp,resist flank and crater wear.

Cons - weak bond to substrates

Question 15

Diamond coating

Answer 15

Best in non-ferrous and abrasive material.

Question 16

Cubic Boron Nitride (material)

Answer 16

Brittle (no vibration)
Must be in dry conditions

Question 17

Silicon nitride based ceramic (material)

Answer 17

Toughness, hot hardness and good thermal shock resistance. Bad for steel due to chemical affinity to iron.
Best for cast iron and nikel based superalloy

Question 18

Diamond (material)

Answer 18

Low friction, high wear resistance, maintain sharp edge, good surface finish, high accuracy. Low rack angle at hugh spd. Best for uninterrupted finishing cut. Bad with carbon steel or titanium.

Question 19

Cutting fluids

Answer 19

Reduce friction and wear, cool cutting zone, reduce forces and energy consumption, flush awy chips, prevent corrosion.

Question 20

Type of Cutting fluids

Answer 20

Oils, emulsion, semisynthetic, synthetic