Everything You Need to Know About Battling Heat Related Tool Wear in CNC Machining

The Ultimate Guide to Battling Heat Related Too Wear

Almost everyone in the machining world, has heard the term “tool wear”. It’s a term every manager and shop owner should know, but it’s often poorly understood. 

Heat is one of the most persistent enemies in machining—aside from machinery limitations, heat is often the primary limiting factor in how fast we can process material in nearly every application.

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Metals & Heat in CNC Machining:

With a few exceptions, when machining metals the heat generated from elevated speeds dramatically accelerates tool wear. Of course, we use the most wear resistant & heat-resistant tool/coating combination that we can, but the speed limits still exist. This mechanism forces us to reduce speed to a more balanced point between tool wear and cycle time.

🔥 Heat Effects on Metal Workpieces from Machining

1. Heat Buildup

• Primary concern with elevated speeds.

• Can cause:

  • Thermal expansion → dimensional inaccuracies

  • Surface hardening (work hardening) in materials like stainless steel

  • Material phase changes in sensitive alloys (e.g., titanium, nickel-based)

    
    

2. Surface Integrity Issues

• High temperatures can degrade surface quality:

  • Burn marks

  • Microcracks

  • Oxidation/discoloration

• In aerospace-grade alloys, surface integrity is critical and must be tightly controlled.

  
  

3. Residual Stresses

• Rapid thermal cycles from fast machining cause non-uniform stress fields in the material.

• Can affect fatigue life and cause warping after machining.

🔥 Heat Effects on Cutting Tools when Machining Metal

1. Accelerated Tool Wear

• Elevated speeds increase:

  • Flank wear

  • Crater wear

  • Notching

• Especially problematic in hard metals (e.g., Inconel, hardened steels).

  
  

2. Tool Edge Deformation or Chipping

• High thermal load softens tool edge if coating/substrate can’t handle it.

• Leads to plastic deformation, edge chipping, or catastrophic failure.

  
  

3. Coating Breakdown

• At excessive temperatures, coatings like TiAlN or TiCN can oxidize or spall off.

• Once coatings fail, the base material wears much faster.

  
  

4. Built-Up Edge (BUE)

• In ductile metals (like aluminum or mild steel), high speeds may encourage material adhesion to the tool edge.

• BUE dulls the tool and worsens surface finish.

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Plastics & Heat in CNC Machining:

When CNC machining plastics at elevated speeds, both the material behavior and the cutting tool performance are affected in ways that differ from metals or composites. Plastics are thermally sensitive, softer, and prone to deformation, so speed must be balanced carefully. The heat generated from machining plastics causes the plastic to exceed its glass transition temperature (Tg), which leads to softening, deformation, or melting which compromises dimensional accuracy & surface finish.

Here’s a breakdown of the effects of elevated speeds when CNC machining plastics:

🔥 Heat Effects on the Plastic Materials from Machining

1. Melting or Gumming

• Thermoplastics (like ABS, nylon, HDPE, polycarbonate) can melt, smear, or gum up when exposed to excessive heat.

• This results in poor surface finish and built-up material on the tool.

  
  

2. Thermal Expansion and Warping

• Elevated heat causes dimensional instability, especially in larger parts or thin-walled sections.

• Warping or softening may lead to inaccurate tolerances.

  
  

3. Burning or Discoloration

• Some plastics (like acrylic or PVC) will burn, char, or discolor at high spindle speeds due to friction heat.

  
  

4. Micro-cracking or Stress Whitening

• Brittle plastics (e.g., acrylic, polystyrene) may crack or whiten under fast, aggressive tool engagement.

• Too high a speed can cause crazing or edge chipping during entry/exit.

  
  

🔥 Heat Effects on Cutting Tools from Machining Plastics

1. Material Buildup on Cutting Edges

• Soft plastics can melt and adhere to tool edges at high speeds, reducing sharpness and cutting effectiveness.

• This leads to gummy buildup or drag marks.

  
  

2. Tool Coating Breakdown

• Certain coatings (like TiN or TiAlN) may retain heat rather than dissipate it, worsening melting.

• Polished uncoated carbide is often better to reduce friction and heat.

  
  

3. Tool Deflection or Breakage

• While plastics are soft, improper high-speed cutting with small-diameter tools can cause deflection or breakage, especially with brittle plastics.

  
  

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Composites & Heat in CNC Machining:

In composites-like carbon fiber reinforced plastics (CFRPs), glass fiber reinforced plastics (GFRPs), and other advanced composite materials, the heat generated elevated cutting speeds can compromise both the material itself and the cutting tool. Because of the abrasive nature of the material, excessive speed can cause rapid tool wear & failure. Excessive machining speeds can soften the polymer matrix (epoxy, thermoplastic, etc.) and lead to delamination, fiber pull-out and burnt surfaces.  

🔥Heat Effects on the Composite Material from Machining

1. Thermal Degradation (Matrix Damage)

• Elevated speeds can generate excessive heat, which softens or degrades the polymer matrix (epoxy, thermoplastic, etc.).

• This can lead to delamination, fiber pull-out, and burnt surfaces, especially in thermoset composites.

  
  

2. Increased Delamination Risk

• Higher speeds may increase forces and vibrations, potentially exceeding the interlaminar strength of the composite.

• This can lead to layer separation, especially at entry/exit points of drilled or milled areas.

  
  

3. Fiber-Matrix Debonding

• The mismatch in thermal expansion between fibers and matrix can cause microcracks or debonding under high temperatures and speeds.

  
  

4. Surface Finish Changes

• At moderate speeds, finish may improve due to cleaner cuts.

• At too high speeds, however, thermal softening and tool wear degrade surface quality (fuzziness, roughness, fiber tearing).

🔥Heat Effects on Cutting Tools from Machining Composites

1. Accelerated Tool Wear

• Abrasive fibers (like carbon or glass) cause rapid flank and edge wear, especially at elevated speeds.

• Tools made from uncoated carbide or HS

  S wear out fast.

  
  

2. Edge Chipping and Tool Failure

• High-speed contact with hard fibers increases the risk of chipping, micro-fractures, and catastrophic tool failure, particularly with brittle tools like PCD (polycrystalline diamond) or ceramic.

  
  

3. Heat Build-up Without Chip Carriage

• Composites don't form continuous chips, so there's little heat dissipation through chips.

• Heat accumulates at the cutting zone, further degrading the tool and material.

What Causes the Heat?

Friction between the cutting tool and workpiece during turning, milling, or drilling, etc. generates intense heat—especially at the cutting edge. If not properly controlled, this heat can exceed the tool material’s thermal limits, leading to:

• Thermal Cracking: Repeated heating and cooling cycles cause micro-cracks that grow and eventually lead to tool breakage.

• Plastic Deformation: Excess heat softens the cutting tool material, weaking the substrate and leading to deformation under cutting loads.

• Oxidation and Chemical Wear: High temperatures trigger surface degradation through chemical reactions with the workpiece or coolant.

• Diffusion Wear: Heat accelerates atomic migration between the tool and workpiece, gradually weakening the tool edge.

Using coolant or lubricants & selecting the optimal cutting tool and cutting speed is a foundational principle in machining best practices, but even then, we are still at the mercy of heat to keep our speed in check.

While heat can never be completely eliminated from the machining process, we are constantly looking for ways to protect both the cutting tool and the workpiece—especially at higher speeds. The better we manage heat, the faster and more efficiently we can machine.

One thought on this subject that has proven to yield impressive results in certain applications is a cryogenic system that is retrofitted to the CNC machine and fires an extremely cold stream of liquid nitrogen to the cutting tool or cutting developed by the industry leader in that space, Industrial Cryogenic Technologies https://industrialcryotech.com/

In the meantime, it is critical to have a deep knowledge of raw materials, cutting tools & tool coatings to get the most bang our buck. Fortunately the solution for that is simple: The G3CNC Tooling & Materials course.

G3CNC Tooling & Materials Course & Combating Heat Related Tool Wear for CNC Set-Up Teams

🎯 Training Focus:

Understanding, identifying, and mitigating tooling & heat-related issues in CNC machining to protect tooling, preserve material integrity, and optimize machine & set-up efficiency.

✅ 1. Improved Tool Life & Cost Reduction

Why it matters: Heat is the #1 cause of accelerated tool wear—leading to frequent tool changes, poor finishes, and higher per-part costs.

How G3CNC Tooling & Materials Course helps:

• Teaches employees how to identify signs of heat-induced wear (flank, crater, notch, plastic deformation)

• Equips them with selection strategies for heat-resistant tool substrates and coatings (carbide, TiAlN, ceramics)

• Covers optimal cutting parameters and coolant strategies to extend tool life

Benefit:💰 Up to 30–50% reduction in tooling costs through proactive heat management and smarter tool selection

✅ 2. Better Surface Finish & Dimensional Accuracy

Why it matters: Heat-induced work hardening, thermal expansion, or melting can degrade surface quality or shift critical dimensions—especially in tight-tolerance aerospace and medical parts.

How G3CNC Tooling & Materials Course helps:

• Explains how heat affects material behavior (e.g., phase changes in metals, melting in plastics, matrix degradation in composites)

• Demonstrates how to adjust speed, feed, and engagement angles to minimize thermal stress

• Trains setup teams to anticipate thermal distortion risks during programming or fixture design

Benefit:🎯 Fewer scrapped parts, improved first-pass yield, and reduced need for secondary finishing (deburring, polishing, sanding)

✅ 3. Optimized Machine Utilization & Throughput

Why it matters: Heat limits how fast you can run your machine. Without understanding thermal effects, employees may run overly conservative programs—or worse, damage tools and parts by pushing too hard.

How G3CNC training helps:

• Teaches the limits of different materials’ heat thresholds and tool tolerances

• Breaks down cutting speed strategies that balance productivity with thermal control

• Introduces advanced cooling technologies (e.g., air blast, MQL, cryogenics)

Benefit:⚡ Increased productivity with smarter, faster setups that avoid overheating or tool failure

✅ 4. Safer, More Confident Setup Technicians

Why it matters: Poor heat management leads to unpredictability, tool breakage, and stress on both the operator and the machine.

How G3CNC training helps:

• Builds a foundational understanding of heat generation and its warning signs

• Empowers employees to prevent problems before they happen, rather than reacting to them

• Encourages proactive decision-making: proper tool pairing, coolant setup, and cutting parameter adjustment

Benefit:🧠 More confident setups, smoother production launches, and fewer unscheduled stoppages

✅ 5. Long-Term Material Knowledge for Modern Applications

Why it matters: Many shops are shifting toward more heat-sensitive and difficult-to-machine materials—like Inconel, titanium, carbon fiber composites, or high-performance plastics.

How G3CNC training helps:

• Teaches material-specific thermal behaviors and strategies (e.g., how to machine composites without delamination or how to avoid melting in thermoplastics)

• Links material degradation to long-term part reliability—especially in regulated industries

Benefit:🔍 Better part quality, fewer defects, and enhanced customer satisfaction in demanding sectors like aerospace, medical, and automotive

📈 Business Impact Summary for G3CNC Tooling & Materials Training

Area	Impact from G3CNC Training
Tooling Costs	↓ Reduced due to longer-lasting tools and better usage practices
Scrap & Rework	↓ Lowered due to improved surface finish and dimensional control
Cycle Time & Throughput	↑ Increased by enabling higher speeds with proper thermal management
Employee Confidence	↑ Grows as understanding of heat’s impact improves
Material Performance	↑ Enhanced by protecting from degradation during machining
Quality & Compliance	↑ Maintained or improved in high-spec applications

Bottom Line:

G3CNC’s CNC Tooling & Materials Training gives your setup team the technical edge to fight machining heat head-on. When your team understands how to control heat, they control the outcome: better tool life, longer sustained machine up-time, better part quality, faster jobs—consistently.

About G3CNC

G3CNC is uniquely impacting the training space for CNC machining to attract more talent into the industry and drive rapid results with educational resources focused on improving employee work ethic and productivity. Unlike traditional training G3 focuses on the "whole person" with job specific skill sets in addition to qualities like work ethic, communication, professionalism & leadership. Using advanced learning methods including online modules & artificial intelligence, we specializes in "capturing" employees into the CNC machining industry, and dramatically boosting employee performance, productivity & employee retention.

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📌 Learn more: www.g3cnc.net

📧 Contact: contact@g3cnc.net