Cutting tools are not new to metalworkers. And even if you are just starting your machining project, you should know that having the right cutting tools is a must. 

These humble workhorses slice, drill, and shape metal as you desire, whether it’s a bicycle frame or a spacecraft component. But the question is, how much do you really know about cutting tools in your workshop?

Maybe you know the basics like – end mills remove material, drill bits to make holes, and so on. However, cutting tools are a surprisingly deep topic with nuance that can dramatically impact your workflow and finished product quality. If you want to tackle tougher jobs with greater precision and efficiency, you must understand more about these essential pieces of equipment. 

Geometry governs performance

Ever wondered how some end mills can cut thick slabs of titanium while others struggle with mild steels? The difference lies in their geometry – the angles, edges, and overall shape designed into the cutting tool.

As a sharp chef knife slices easier than a blunt kitchen knife, optimized cutting tool geometries allow the tip to efficiently shear through tough materials with minimal friction and heat buildup. Manufacturers apply different geometry strategies for various applications:

  • The roughing tools have thick and tough inserts made to remove huge quantities of materials quickly.
  • On the other hand, finishing tools are concerned about producing perfect surface finish rather than aggressive material removal.
  • Tools for hard materials such as stainless steel have very positive rake angles and sharp cutting edges that reduce friction and prevent chipping.

From tools to super tools with coatings

Are you working with superalloys, hardened steels, or even abrasives like carbon fiber composites? So you’ll definitely look at cutting tools that have advanced coatings in them that can withstand high temperatures and avoid wearing out prematurely or breaking down.

To put it simply, these are very thin layers made up of ultra-hard substances that are placed on the surface of a tool through vapor deposition processes. Among the most widespread high-performance coatings are:

  • Titanium Nitride (TiN): A golden yellow color provides excellent lubricity and wear resistance on steel as well as cast iron. It is cheap but has no oxidation resistance at high temperatures.
  • Titanium Aluminum Nitride (TiAlN): Purple-black colored coating which shows hot hardness > 1800°C, thus suitable for high-speed machining of aerospace alloys. 
  • Diamond Coatings: Ultimate hard, slick coating – but expensive, too. Typically used to machine such super-abrasive materials as CFRP (Carbon Fiber Reinforced Polymers).

Don’t overlook the substrate material.

The underlying tool substance or “substrate” is crucial, even when the focus is mostly on cutting tool geometries and coatings. It actually provides the core toughness and essentially enables the coatings and geometries to work as they should.

Most economical cutting tools make use of basic substrates such as high-speed steel (HSS). In fact, HSS is a versatile, inexpensive option for machining aluminum, mild steel, plastics, and wood.

However, HSS can suffer in harder materials or at high temperatures. That’s where more expensive substrate materials like solid carbide, cermet, and polycrystalline diamond (PCD) come into play:

  • Tungsten Carbide (solid carbide): By far the best choice when it comes to machining hardened steels, stainless steels, superalloys like Inconel, and heat-resistant super alloys (HRSA). Remains hard at high temperatures.
  • Ceramic/Metal Composite (cermet): Very hard material with a low wear rate. This would be excellent for abrasive materials like carbon fiber, which dissolve carbide tools very fast, but this material tends to be brittle.
  • PCD: Probably the hardest and most enduring cutting tool material available. Though also by far the most expensive one. It cuts non-ferrous materials such as aluminum and abrasive ceramics well enough.

Treat your tools right.

Neglecting proper care and maintenance is a huge mistake, for you can never get the best out of any cutting tool, no matter how expensive it is. Here are some basic tips to take care of your cutting tools:

  1. Use an adequate coolant flow to prevent overheating and wash away chips
  2. Check regularly for excessive wear and replace inserts/tools as required
  3. Handle tools with coatings with care so as not to chip delicate surface
  4. Keep tools in a clean, dry environment to avoid corrosion
  5. Follow recommended manufacturer speeds/feeds for extended tool life

Do not just “set it and forget it” on your cutting tools. Watch the wearing patterns and anticipate changes before they become catastrophic failures. Create rapport with your cutting tool provider for expert advice on optimum speeds/feeds and application guidelines.

When you choose, prepare for, and take care of your cutting tools well, there is no machining task you cannot handle confidently — from simple tasks to complex, lights-out production runs. There are always more things to know: tool geometry, coatings, materials used for its manufacturing and maintenance will immediately enhance your skills as a machinist.

Therefore, be knowledgeable about cutting tools and how you handle them with the kind of respect they should be accorded. Their hard work in workshops provides easier machinability, longer life of the tool as well as better finished parts.