Blog

Apr 01, 2025

A look at insert wear management

Optimizing the insert geometry, the configuration of the cutting edge, material, and coating will help improve insert wear as it is better suited for the application and less likely to have unexpected

Optimizing the insert geometry, the configuration of the cutting edge, material, and coating will help improve insert wear as it is better suited for the application and less likely to have unexpected failure.Kennametal

Insert wear is inevitable, but its impact is far reaching. Despite being a small part of the overall manufacturing cost, properly maintained inserts help ensure productivity, safety, and economic efficiency of the machining process.

The challenge lies in knowing when an insert’s performance decline risks failures that could lead to damaged workpieces, tooling, or even injuries.

In aerospace manufacturing, where workpieces can exceed $100,000, running a $6 insert past its safe limit is a high-stakes gamble. Even in operations that produce low-cost components, overusing an insert can lead to machine damage, compromised safety, and increased costs.

Understanding insert wear and applying six best practices can optimize tool life, improve efficiency, and ensure safety.

Not all projects are created equal, not all manufacturers have the same production demands, and not all customers want the same thing.

It’s important to start with an understanding of goals. Should you focus on performance security and stability? Or is the highest productivity level the most important? For any process optimization, there may be a significant investment in time that the production volume and component value may not warrant.

“If there is a thin margin on a job, you wouldn’t want to spend the time required to optimize it,” said Brian MacNeil, milling products and application specialist at Sandvik Coromant, Mississauga, Ont. “This is especially true if the part is one that you don’t expect to see again. If it’s a repeat job, then optimization can help you become more profitable on future jobs, but that depends on the margins.”

Sometimes a compromise is necessary when it comes to running efficiently and ensuring quality. MacNeil cited an aerospace customer in Quebec that spent a week tracking what was happening at the cutting edge to understand when to back off the speeds and feeds for safety and security to get through the shift. The idea is that for those looking to run lights-out machining, they need to understand the wear on the cutting tool insert - and adjust cut data to improve it - making the process secure.

“For a production part running day in and day out, it is a lot easier to determine how an insert or tool is going to behave,” said Darryl Latoski, milling product manager at ISCAR Tools, Oakville, Ont. “For example, in the automotive industry, they can set a tool where, if all goes well, the tool should produce a specific number of parts. On the job shop side of things, this can be more difficult and require a skilled operator to understand insert life and wear conditions.”

Knowing about the variables that affect how the insert wears will give better insights into its potential lifecycle. For example, an insert can run for much longer when cutting aluminum, because it is a softer material, than it could with cast iron, steel, or titanium.

One of the biggest mistakes shops make is not taking the time to train operators to better understand the progression of wear. There are different ways inserts wear and different failure modes of the cutting tool. Providing reference materials like charts and graphics along with having discussions about mitigating issues can go a long way. Sandvik Coromant.

For lights-out operations, it is critical to have process security and a good understanding of what’s happening at the cutting edge. Without this, you risk catastrophic failure that leads to significant downtime and potential damage to the workpiece, machine, and tooling.

Each application has different characteristics that require attention. An expectation of high productivity without an insert geometry and grade that can achieve it will cause you to push inserts beyond their capabilities, leading to catastrophic failure.

There is a push in many shops to reduce inventory and choose more generic tools to cut a larger variety of materials and applications. One coating and one geometry are not always sufficient.

Optimization often includes introducing higher-quality and harder inserts that can deal with increased speed. It is important to program in such a way that the insert is protected and can still achieve high productivity. If you introduce chatter and interruptions into an area, this will damage a brittle insert.

“There are a variety of different geometries, and that will affect the rake angle, hone size, or the edge prep on the insert, anything from up sharp, a small hone, to even a T-Land,” said Luke Pollock, senior global product manager – indexable milling, Kennametal, Latrobe, Pa. “The grade is typically made up of the substrate or the base material of the insert, and then there is usually some sort of coating. All these features combine to make an insert more appropriate for one material or one type of machining, whether roughing versus finishing, over another.”

Optimizing the insert geometry, the configuration of the cutting edge, material, and coating will help improve insert wear as it is better suited for the application and is less likely to fail unexpectedly.

For example, choosing a harder insert grade for abrasive materials will allow it to last longer in the cut.

“With abrasive materials, have a reinforced cutting edge to better withstand the impact and the abrasiveness of the workpiece,” said Latoski. "If it's a finishing cut or a softer material, use sharper cutting edges or geometries.”

Coatings also affect insert wear rates.

For example, chemical vapour deposition (CVD) coatings allow the insert to be run at much higher speeds and make it more productive in production environments.

Ideally, wear should progress evenly and consistently until it reaches a certain level and can no longer be used. Figure 1 shows flank wear, which is very common and the type of wear you want to see. Figure 2 shows notch wear, which causes poor surface finish and risk of edge breakage. Figure 3 shows small fractures in the cutting edge (frittering), causing poor surface finish and excessive flank wear. Figure 4 shows the part of the cutting edge not in the cut damaged by chip hammering. ISCAR

Physical vapour deposition (PVD) coatings are generally better suited for lower surface speeds, finishing applications, and high-temperature alloys.

Fixturing is extremely important. Parts that are not rigid, parts that are hanging out, or parts that require a long reach can cause chatter and vibration in the cutting edge.

“Vibrations and chatter can be abusive to the cutting edge of the insert,” said Pollock. “It can cause chipping, breaking, or other failure modes. Make sure the part is fixtured as rigidly as possible and in the machining direction. If you're feeding in the Z direction, you want to make sure your fixture is rigid in that direction. If you're feeding in the X and Y, make sure you're clamped for those cut types.”

Quality part fixturing reduces chatter and vibration, leading to longer tooling life and reducing failure risks.

Training is essential to help operators better understand insert wear, especially as a lot of longtime employees retire, taking tribal knowledge with them.

Visual charts can demonstrate wear characteristics and can be displayed on the shop floor. But according to MacNeil, more effort is necessary.

“It’s more than just putting up a chart, though,” said MacNeil. “Take the time to share with operators exactly what’s on the chart and the basic remedies for the wear characteristics for inserts. There are troubleshooting actions for each that are important for operators to know. A small investment in training can help workers better identify wear issues and what exactly is happening at the spindle and adjust accordingly.”

When it comes to uncommon wear issues, a bigger discussion on how to better mitigate any issues should take place between programmers and operators.

A trained ear can often hear when there is an uncommon wear issue. Depending on the material, operators should listen for heavy burring on a part and assess the situation. Vibration also can indicate wear issues.

“A good machinist will hear the machine from far away and know that something has changed,” said MacNeil. “A lot of times you can hear when you've lost a single corner. But that comes down to experience and training. By investing in the people running the machines, they have an investment in you too. It’s a two-way street that is beneficial for all.”

“The most common mistake is not taking the time to understand the progression of wear,” said MacNeil.

There are different ways inserts wear and different failure modes of the cutting tool.

Ideally, wear will progress evenly and consistently until the insert reaches a certain level and can no longer be used.

For example, flank wear, the natural breakdown of the cutting edge, is very common and the type of wear you want to see.

Take time to monitor the insert by stopping at certain intervals to note how the tool wears over time. This can help determine a safe number of parts or minutes that the insert should be used for before it should be replaced.

“For example, if it has been determined that a shop can get 100 parts from an insert, they can set the tool to be changed after a certain number,” said Pollock. “For more expensive parts, that safety margin will be much wider, say at the 65 mark, to reduce the risk of scrapping the part. Others could go closer to 90.”

It’s important not to push the insert beyond its capacity, which can lead to breaking, fracturing, and destructive damage. Monitoring will help catch insert wear before it reaches that point, allowing the operator to change the tool or cutting edge.

“Your capability studies as you go through your production part approval process (PPAP) will help determine insert wear and predictable tool life,” said Latoski. “You have to take a look at wear as you're developing a process, take a look at the insert, see how it's wearing, and, depending on the different wear factors, adjust accordingly.”

With a wide variety of technology available, including options that can help reduce insert wear and lead to longer tool life, you need to ensure your machines are able to accommodate it.

Spindle load monitoring stops the machine when a tool puts too much load on the spindle. Some machines also can make use of a sister tool.

“But that requires an investment in a larger tool changer,” said MacNeil. “This is why it’s important to think ahead when it comes to investing in new equipment. If you are cutting high-nickel-based alloys, titanium, or INCONEL; large-volume, high-pressure coolant is a must. If you are cutting steel, air is preferable. Knowing what you are investing in will help ensure that you get the most life out of your cutting tool.”

Advanced tools can be added to machines to provide control, real-time feedback, and measure changes in horsepower, cutting forces, and tooling pressure.

“They are all designed to give the machine feedback of what’s going on at the cutting edge,” said Pollock. “It can do something as simple as warn the operator that the machine has reached the set limit or go as far as optimize the feeds and speeds in real time.”

Load meters, whether digital or analog, will provide a visual indicator of how much load is being placed on the spindle or the particular axis on the machine. They also can alert operators if something starts to go wrong with the insert.

“Without being warned of a load error, operators can run the inserts to failure, which can lead to not only a damaged insert but a damaged tool cutter body and other components on the machine,” said Latoski. “Surface finish can be affected by insert wear, and sometimes it’s not always visually identifiable in the insert. The surface finish results can be analyzed via statistical analysis to determine parameters to make sure that you understand the process and how many parts can be made using a single insert before the surface finish is affected. Many technologies work together with the inserts and machine to make automatic adjustments or stop the machine if the insert is starting to wear.”

Senior Editor/Digital Editor Lindsay Luminoso can be reached at [email protected].

ISCAR, www.iscar.com

Kennametal, www.kennametal.com

Sandvik Coromant, www.sandvik.coromant.com