Identifying and Addressing 8 Common Blade Failure Modes

Blade failure and its detrimental effects on production equipment are akin to an athlete wearing out a pair of high-quality running shoes. Just as the shoes bear the athlete’s weight repeatedly, blades endure immense stress cycles, leading to wear and tear over time. If left unaddressed, this wear can cause discomfort for the athlete—and, in a manufacturing setting, it can compromise both the precision of the machining process and overall productivity. However, manufacturers can take proactive steps by carefully analyzing the cutting tools they use, enabling them to maximize tool life, predict tool performance, and ultimately maintain part accuracy while minimizing declines in equipment efficiency. Early blade inspections are crucial for pinpointing the root causes of failure, as this is when issues are most easily observed and documented. Without these critical steps, there’s a risk of misinterpreting or conflating different types of failure modes. To facilitate thorough blade inspections, a stereo microscope is an ideal tool. With its superior optical capabilities, ample lighting, and magnification ranging from 20x upward, it proves invaluable in identifying the specific failure mechanisms responsible for premature blade wear.

Rear flank wear

Normal wear on any type of material can lead to blade failure. Flank wear is the most common form of wear because it’s the easiest tool failure mode to predict. Typically, flank wear occurs uniformly as the cutting edge gradually deteriorates due to the material being machined—much like a blade becoming dull over time.

Normal flank wear occurs when hard, fine inclusions or work-hardened material in the workpiece cut into the cutting edge. This type of wear is caused by abrasive wear during low-speed cutting and chemical reactions at high speeds.

When identifying normal flank wear, you’ll notice a relatively uniform wear mark forming along the cutting edge of the blade. Occasionally, metal from the workpiece may rub against the cutting edge, artificially exaggerating the apparent size of the blade’s wear marks.

To slow down normal flank wear, it’s crucial to use the hardest blade material grade that avoids micro-chipping, as well as the lightest, most efficient cutting edge to minimize cutting forces and friction.

On the other hand, rapid wear on the flank face is undesirable, as it reduces tool life and prevents achieving the typical 15-minute cutting time. Rapid wear often occurs when machining wear-resistant materials such as ductile iron, silicon aluminum alloys, high-temperature alloys, precipitation-hardened (PH) stainless steels after heat treatment, beryllium copper alloys, and tungsten carbide, as well as when cutting non-metallic materials like fiberglass, epoxy resins, reinforced plastics, and ceramics.

Signs of rapid flank wear resemble those of normal wear. To address rapid flank wear, it’s crucial to select carbide insert grades that are more wear-resistant, harder, or coated—along with ensuring the use of appropriate coolant. Reducing cutting speed can also be effective, but this often conflicts with production needs, as it would negatively impact the machining cycle.

Crescent-shaped depression

Moon-shaped depressions commonly occur during high-speed machining operations involving iron-based or titanium-based alloys—they represent a thermal/chemical issue where the cutting tool dissolves into the workpiece chips.

Diffusion wear and abrasive wear together contribute to the formation of crescent-shaped depressions, known as "grovelling." When machining base metals and titanium-based alloys, the heat generated by the chip can cause the hard alloy components to dissolve and diffuse into the chip, leading to the development of these characteristic depressions on the top of the cutting tool. Over time, these grooves may grow large enough to induce micro-chipping or deformation on the flank face—or even accelerate severe flank wear.

Built-up edge

When workpiece fragments are thermally welded onto the cutting edge during hot pressing, built-up edges form—resulting from chemical affinity, high pressure, and elevated temperatures in the cutting zone. These built-up edges eventually detach, sometimes even breaking off along with chip fragments, leading to micro-chipping and rapid flank wear.

This failure mechanism is commonly observed in viscous materials, low-speed applications, high-temperature alloys, stainless steels, and nonferrous metals—as well as in thread machining and drilling operations. Built-up edges can be identified by abnormal changes in workpiece dimensions or surface roughness, as well as by the presence of shiny material on the cutting edge or the flank face of the tool.

Accumulated built-up edges can be controlled by the following methods: increasing cutting speed and feed rate, using carbide-coated (TiN) blades, optimizing coolant usage—such as boosting its concentration—and selecting tools with geometries that reduce cutting forces and/or blades featuring smooth surfaces.

Slight collapse

Micro-chipping originates from unstable mechanical performance, typically caused by loose clamping, poor bearing conditions, spindle wear, or the presence of hard inclusions in the workpiece material, as well as intermittent cutting. This phenomenon can sometimes occur unexpectedly—such as when machining powder metallurgy (PM) materials intentionally designed with porous structures embedded in the part. Hard inclusions within the surface of the cutting material and intermittent cutting actions can lead to localized stress concentrations, ultimately triggering micro-chipping.

In this failure mode, chips distributed along the cutting edge of the blade are particularly noticeable. To prevent micro-chipping, ensure proper machine tool clamping, minimize bending deformation, use ground blades, control built-up edges, and opt for blade materials with improved toughness and/or cutting-edge geometries that offer greater strength.

Severe temperature fluctuations combined with mechanical shock can lead to thermomechanical failure. Stress cracks may develop along the cutting edge of the blade, eventually causing the hard alloy portion of the blade to detach—appearing somewhat similar to micro-chipping.

Thermo-mechanical failure is most likely to occur during milling operations, but it can also appear in intermittent turning of large-batch parts, face milling, and machining processes that utilize intermittent coolant application. A key indicator of thermo-mechanical failure is the presence of multiple cracks running perpendicular to the cutting edge. Identifying this failure mode early—before micro-chipping sets in—is particularly critical.

To prevent thermomechanical failure, you can: properly use coolant, or, if you want to eliminate this type of failure entirely from your machining process, opt for a more impact-resistant material grade, along with a groove geometry that minimizes heat generation and reduced feed rates.

Excessive heat and mechanical loads are the root cause of cutting edge deformation. At high speeds and feed rates—or when machining hard steels, work-hardened surfaces, or high-temperature alloys—significant amounts of heat are often generated.

Excessive heat can cause the hard alloy binder or cobalt in the cutting blade to soften. When stress between the blade and the workpiece leads to blade deformation or chipping at the cutting edge, it creates mechanical loads that may eventually result in blade fracture or rapid flank wear.

Signs of cutting edge deformation include distortion of the cutting edge and workpieces that fail to meet dimensional specifications. To control edge deformation, consider the following measures: properly use coolant, opt for more wear-resistant material grades with lower adhesive content, reduce machining speed and feed rate, and employ a flute geometry designed to minimize cutting forces.

Groove wear occurs when the rough surface of a workpiece rubs against and scratches deep into the cutting zone of the tool. Casting surfaces, oxidized surfaces, work-hardened surfaces, or even irregularly shaped surfaces can all contribute to groove wear. While abrasive wear is typically the primary culprit, micro-chipping may also take place in this area. The cutting-edge line of the blade often experiences tensile stress, making it particularly susceptible to damage.

This failure mode becomes significant when groove wear and micro-chipping begin to appear at the cutting depth of the blade. To prevent groove wear, it’s crucial to vary the cutting depth during multi-pass machining, employ tools with a larger rake angle, increase cutting speeds—and reduce feed rates—when working with high-temperature alloys. Additionally, carefully control grinding at the cutting depth to avoid built-up edge formation, especially when machining stainless steel and high-temperature alloys.

When the force acting on the cutting edge exceeds its inherent strength, the blade will experience mechanical failure. Any failure mode discussed in this paper could potentially lead to mechanical rupture.

In addition to normal flank wear, mechanical failure can be prevented by addressing all other potential failure modes. Effective corrective measures include using material grades with higher impact resistance, selecting blade geometries that offer greater strength, opting for thicker blades, reducing feed rates and/or cutting depths, ensuring proper clamping rigidity, and verifying that the workpiece is free of hard inclusions or materials that are difficult to cut.

By understanding these 8 common failure modes and developing failure analysis skills, manufacturers are sure to reap significant benefits. Key advantages include increased productivity, enhanced tool life and consistency, improved part accuracy and aesthetics, reduced wear and tear on equipment, and a lower likelihood of severe blade failures—ultimately preventing production disruptions and ensuring critical tasks remain unaffected.

Headquartered in Fagersta, Sweden, ShanGao is dedicated to developing innovative metal-cutting solutions. We work closely with our customers to gain a deep understanding of their needs and tailor our offerings precisely to meet them—earning us a global reputation for excellence. Today, we employ over 5,000 people across 50 countries, empowering our team members through comprehensive training, development programs, employee engagement initiatives, and an open communication environment. At ShanGao, our employees embody three core values: passionate customer care, a strong sense of family and belonging, and personal commitment—values that guide how we operate and shape our relationships with customers, suppliers, and other partners worldwide.