Cutting Tool Types and Observation and Inspection Using a Digital Microscope

The faster the cutting speed,
the higher the productivity,
but
the shorter the service life of the tool.

As the feed speed increases,
productivity increases
but
so does the roughness of the cut surface.

The greater the cut amount,
the higher the productivity,
but
the ideal cut amount is determined by the type and material of the tool.

• Turning
  Generally, this method cuts cylindrical or discoidal workpieces into round shapes by turning them.

• Drilling
  Tools rotate to make holes in surfaces of workpieces.

• Boring
  Tools rotate and machine the inside of drilled holes with high accuracy.

• Broaching
  Broaches (tools to finish holes) cut workpieces by moving linearly. Broaching can perform a whole process (through to finishing) with one machine, and it’s easy to estimate the service life of tools. These factors make broaching attractive to the automotive industry where mass production is necessary.

• Gear cutting
  Gears are cut with a rotating cutter.

Machine name: Gear cutting machine
Cutting tool: Hob cutter, pinion cutter, rack cutter

• Milling
  Milling removes material by turning a tool called a milling cutter. Milling machines are used to shave surfaces and make grooves. There are generally 2 types: face milling cutters for surface machining, and end mills for grooving.

This section describes the materials and features of typical cutting tools.

• High-speed steel
  Metals, including tungsten, chromium, vanadium, and molybdenum, alloyed with an iron base
  Advantage Excellent toughness
  Disadvantages Lower heat and wear resistance
  Target materials: Carbon and alloy steel
• Cemented carbide
  Alloys of titanium carbide and tantalum carbide that are added to tungsten carbide powder and then sintered using cobalt.
  Advantages Excellent balance of toughness, high hardness, and wear resistance
  Target materials: Carbon steel, alloy steel, stainless steel, and other cutting resistant materials
• Ceramic
  Hard materials, including aluminum oxide, titanium carbide, and silicon nitride, that are sintered.
  Advantages Excellent heat and wear resistance
  Disadvantages Poor toughness and chip easily
  Target materials: Cast iron, heat-resistant alloys, quenched steel, and tool steel
• Diamond
  Molded material made from diamond monocrystal (the hardest material)
  Advantages Excellent heat and wear resistance, and suitable for mirror face cutting
  Disadvantages Poor toughness and chips easily
  Target materials: Non-ferrous metals including aluminum
• Sintered diamond
  Polycrystalline body made by adding cobalt to fine diamond powder and sintering.
  Advantages Excellent heat and wear resistance, and higher toughness than diamond
  Disadvantage Hard to make sharp edges
  Target materials: Non-ferrous metals, cemented carbide, ceramics
• Cermet
  Nickel and other materials are added to titanium carbide and titanium nitride and then sintered.
  Advantages A type of cemented carbide. Excellent wear and corrosion resistance compared with normal cemented carbide. It is often used for finishing steel.
  Target materials: Carbon and alloy steel

The benefit is that the edge is replaceable and it can be used immediately after replacement.
Throwaway tips are mechanically fixed in holders with screws before use. The material for the edge is generally cemented carbide and the shapes are defined by the ISO (e.g., equilateral triangle, square, rhomboid, and circle).

Chipping on a hob cutter edge

3D observation showed that what was thought to be chipping was actually adhesion.

Multi-lighting allows easy observation of the starting point of a fracture surface.

Optical Shadow Effect Mode allows for observation of waves on a cut surface, which is conventionally only possible by using an interferometer, in just a few seconds.