Tool wear can never be completely avoided in metalworking. Where the cutting edge and the workpiece come into contact under high forces, temperatures, and friction, the tool wears down over time. Therefore, the key is not to prevent wear entirely, but to keep it under control and delay it for as long as possible.
The key factors here are the correct cutting parameters, tool geometry suited to the material, appropriate coatings, reliable cooling and lubrication, and a stable machining process. It is equally important to regrind tools in a timely manner before normal wear and tear turns into irreparable damage.
Taking a systematic approach to tool wear not only extends the service life of your tools, but also has a positive impact on production quality, process reliability, and tool costs per component.
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What is meant by tool wear?
Tool wear refers to the gradual change or wear of the cutting edge during machining.
During milling, drilling, or other machining processes, the tool is subjected to both mechanical and thermal stresses simultaneously. The rate at which wear develops depends, among other things, on:
- the material to be machined
- Tool Material and Cutting Edge Geometry
- Cutting Speed and Feed Rate
- Delivery and Conditions for Intervention
- Cooling and Lubrication
- Machine and Clamping Stability
- Tool Coating
- Chip Removal
A certain amount of wear is completely normal. It becomes a problem, however, when it progresses too quickly or is not detected in time. This is because a worn tool affects not only the cutting edge itself but the entire manufacturing process.
What are the different types of tool wear?
Tool wear can manifest in a variety of ways. The wear pattern often provides important clues as to where the cause lies in the machining process.
Open-Surface Wear
In free-surface wear, the tool cutting edge is worn away along the surface that runs along the workpiece that has already been machined. Uniform rake face wear is generally a normal part of a cutting tool’s service life. However, if it becomes excessive, dimensional accuracy and surface quality may deteriorate.
Piston Ring Wear
Tool wear occurs on the tool’s cutting edge. The chip being removed, as well as the high temperatures generated during the process, place continuous stress on the surface. If this wear progresses significantly, the cutting edge can become increasingly weakened.
Chips on the cutting edge
Small or large chips in the cutting edge are often an indication of high mechanical stress, vibration, or unfavorable cutting conditions. Unlike uniform wear, such damage often occurs suddenly and can quickly render the tool unusable.
Building-up Cuts
With a built-up cutting edge, material adheres to the actual cutting edge. This temporarily alters the tool’s geometry. This can degrade the surface finish and result in damage to parts of the actual cutting edge when the built-up cutting edge is removed.
Notch wear and thermal damage
Under certain machining conditions, wear can be particularly concentrated in specific areas of the cutting edge. Extreme temperature fluctuations can also cause cracks and other damage. Fluctuating loads, in particular, make it clear that tool wear must always be considered in the context of the entire process.
How does tool wear affect manufacturing quality?
A worn-out tool can affect the quality and cost-effectiveness of an entire manufacturing process.
Typical consequences include:
- poorer surfaces
- Dimensional and Geometric Deviations
- increasing shear forces
- increased heat generation
- stronger vibrations
- Burr formation on the workpiece
- declining process reliability
- Tool breakage
- unplanned machine downtime
In mass production in particular, even gradual wear and tear can be problematic. For example, if dimensions or surface finishes change across multiple components, scrap may result before the problem is even detected.
Effective tool management, therefore, does not focus solely on maximum service life. What matters most is how long a tool can operate reliably within the required quality parameters.
How can tool wear be reduced?
There is no single solution to tool wear. In practice, it is usually the interplay of several factors that is decisive.
1. Choose the correct cutting parameters
A very high cutting speed can lead to excessive heat generation, thereby accelerating certain wear mechanisms. At the same time, inappropriate feed rates or depth of cut can cause mechanical overload on the cutting edge.
Therefore, cutting speed, feed rate, and depth of cut should always be matched to the tool, material, and machining strategy.
However, it is not necessarily true that less load means less wear. If parameters are selected too conservatively, this can also result in an unfavorable machining process.
The goal, therefore, is not to achieve the lowest possible values, but rather stable and economical cutting conditions.
2. Use the appropriate tool geometry
Cutting geometry, rake angle, clearance angle, cutting edge preparation, and the chip space directly influence how the tool engages with the material.
A geometry that works exceptionally well with aluminum is by no means necessarily the best solution for stainless steel or other materials that are difficult to machine.
Therefore, especially when facing recurring tool life issues, it is worth asking: Is the tool really optimally designed for the specific machining process?
This is exactly where customized tool geometry can offer significant advantages.
3. Select the appropriate tool coating
Coatings can protect the tool surface from wear and affect friction and thermal stresses.
However, there is no one-size-fits-all answer to which tool coating extends service life the most. The material, machining strategy, temperatures, and operating conditions are always the deciding factors.
Depending on the application, different PVD coating systems are used, for example. Coatings based on TiAlN or AlTiN are used, among other things, in thermally demanding applications. Other coatings can offer advantages in terms of friction or wear resistance for certain materials.
Therefore, the best coating is not necessarily the one that is technically the most sophisticated, but rather the one that is best suited to the actual application.
Especially after regrinding, this is an opportunity to realign the coating and the tool geometry.
4. Optimize cooling and lubrication
The right cooling and lubrication strategy can reduce heat, influence friction, and aid in chip removal.
The key factor here is not only whether a cooling lubricant is used, but also:
- whether it reliably reaches the cutting zone
- which cooling lubricant is used
- the pressure at which the system operates
- whether the tool and machining process are suitable for the strategy
Inadequate chip removal can also contribute to wear. If chips are recut or remain in the work area, this results in additional mechanical and thermal stresses.
5. Check concentricity, clamping force, and machine stability
Even a high-quality solid carbide end mill can wear out prematurely if it is not clamped properly.
If concentricity is poor, individual cutting edges are subjected to greater stress than others. This results not in uniform wear, but in localized overloading.
Vibrations and unstable clamping conditions can also cause chipping along the cutting edge and poor surface finish.
For this reason, the tool holder, clamping devices, machine condition, and workpiece clamping are always included in the root cause analysis.
6. Detect wear early
One of the most common mistakes is to continue using a tool until the machining quality deteriorates significantly or individual cutting edges are already severely damaged.
This isn’t always the best approach for maximizing tool life.
Those who inspect their tools regularly and establish defined wear limits can take action sooner. This increases process reliability and, at the same time, improves the conditions for subsequent regrinding.
A recent research project at the IFW at Leibniz University Hannover also demonstrates just how important it is to monitor tool wear in modern milling processes . The project is investigating how tool wear can be measured during machining and how process parameters can be adjusted accordingly throughout the tool’s entire service life.
7. Resharpen tools in a timely manner
A tool that has reached the end of its initial service life does not necessarily have to be replaced. High-quality solid carbide milling and drilling tools, in particular, can be professionally reground and recoated, depending on their condition .
Timing plays a key role in this process. If only the intended cutting zone is worn, the conditions for reconditioning are often favorable. If, on the other hand, tools are used well beyond the economic wear limit, chipping or further damage may occur, making regrinding difficult or impossible.
Early regrinding therefore not only means longer service life per use, but can also extend the overall service life of a tool.
Analyze tool wear instead of just replacing tools
If a tool consistently wears out much sooner than expected, it is often not enough to simply replace it with a new one.
Because if the root cause lies in the process, the same problem could occur again with the next tool.
A systematic approach makes more sense:
- What type of wear pattern occurs?
- How long does it take to produce?
- What materials are processed?
- Which cutting parameters are used?
- How do cooling and chip removal work?
- Are there any abnormalities in concentricity or machine stability?
- Is the tool geometry suitable for the actual application?
Based on this information, potential causes can be narrowed down much more precisely. This is precisely what distinguishes a simple tool change from true process optimization.
Regrinding and Optimization at Kopp Schleiftechnik
At Kopp Schleiftechnik, we don’t automatically consider a worn tool to be spent.
For suitable tools, we first inspect the existing wear and assess the potential for professional regrinding. Depending on the application, it may make sense not only to restore the original cutting geometry but also to specifically adapt the geometry, cutting edge preparation, or coating to the actual application. After all, the goal is a tool that operates as reliably, precisely, and cost-effectively as possible in your process.
That is why a more detailed analysis is particularly worthwhile when dealing with recurring tool life issues. After all, noticeable tool wear can provide valuable clues as to where there is still room for optimization in the manufacturing process.
Frequently Asked Questions About Tool Wear
Can tool wear be completely prevented?
No. Tool wear is an inherent part of machining. However, the rate of wear can be significantly influenced by selecting the right tools, using appropriate cutting parameters, applying suitable coatings, and maintaining stable process conditions.
Which coating provides the best protection against tool wear?
There is no single coating that is best for all applications. The right choice depends, among other factors, on the material being machined, the temperatures involved, the machining strategy, and the tool geometry. The coating and the specific application should therefore always be considered together.
When should a milling cutter be resharpened?
Ideally, this should be done before severe chipping of the cutting edges or other irreversible damage occurs. Defining service life limits or wear limits helps ensure that tools are removed from the process in a timely manner and that their regrinding potential is maximized.
How can you tell if there is excessive tool wear?
Signs of wear may include poorer surface finish, dimensional deviations, increased cutting forces, louder noise, vibrations, or visible changes to the cutting edge.
Conclusion: Reducing tool wear starts with the right process
Tool wear cannot be avoided, but it can be specifically managed.
The right combination of tool geometry, coating, cutting parameters, cooling, stable clamping, and regular inspection ensures that cutting tools can better realize their potential.
Equally important is choosing the right time for reconditioning. Those who use a high-quality tool until it completely fails may be wasting some of its regrinding potential. On the other hand, those who systematically monitor wear can better plan tool life cycles and reduce their tool costs in the long term.
Would you like to know why your tools are wearing out unusually quickly, or whether it’s still worth having them resharpened?
Talk to our team at Kopp Schleiftechnik. We’ll inspect your tools and work with you to develop a solution that fits your manufacturing process. Contact us now or Launch the launch the tool configurator directly.