In our previous article, we explained the first five typical wear modes of solid‑carbide end mills: uniform flank wear, crater wear, minor edge chipping, built‑up‑edge wear and groove wear, including their features, root causes and practical countermeasures.
This article continues with the remaining six tool‑failure types: chip‑evacuation wear, thermochemical‑corrosion wear, plastic deformation, impact chipping, thermal‑cracking wear and catastrophic tool breakage. Many of these are severe damage modes. Without timely adjustments, they may lead to premature tool scrapping, defective workpieces or even spindle damage. Let’s dive into the details.
Chip Evacuation Wear
Features
Chips fail to discharge smoothly and rub flutes & cutting edges repeatedly, creating groove‑like edge damage. Similar appearance as groove wear but totally different inducement.
Root Cause
Small helix angle, excessive cutting depth, unreasonable feed rate, material‑tool mismatch blocking chip flow.
Solutions
- Reduce cutting depth to ease chip evacuation load;
- Choose tool grades compatible with workpiece material;
- Adopt end mills with large helix angles to enlarge chip channels;
- Lower feed rate or cutting depth to cut chip volume.
Thermochemical Corrosion Wear
Features
Chemical reaction occurs between workpiece and carbide substrate under high temperature; surface carbide peels off. Usually accompanied by crater wear and pitting.
Root Cause
Inadequate cooling, thermal diffusion, coating with poor high‑temperature corrosion resistance.
Solutions
Full continuous cooling, reduced cutting speed, tools with high‑temperature resistant coatings.
Plastic Deformation (Edge Softening & Collapse)
Features
Cutting heat softens carbide cutting edges, leading to edge extrusion deformation and collapse. Common in machining high‑hardness & high‑tensile alloys.
Solutions
Lower cutting speed, sufficient cooling, solid carbide tools with ultra‑high hardness substrate.
Impact Chipping (Large‑Scale Edge Breakage)
Features
Massive edge tooth breakage caused by strong impact during entry, exit and interrupted corner cutting, classified as severe destructive wear.
Solutions
Reduce feed rate when engaging/disengaging material, use arc transition for corner paths, apply trochoidal milling, improve overall system rigidity.
Thermal Cracking Wear
Features
Network micro‑cracks spread on edges from frequent heating & cooling cycles. Crack expansion will finally cause total tool chipping.
Solutions
Sufficient continuous coolant supply, avoid dry intermittent cutting, stabilize cutting speed without sharp fluctuations.
Catastrophic Tool Breakage (Critical Failure Warning)
Features
Complete tool fracture, shank breakage or whole cutting head falling off. It is the final failure result of untreated minor wear accumulated during processing, which may seriously scratch workpieces or damage machine spindles.
Solutions
Stop machining immediately once minor chipping, groove wear or thermal cracks appear; inspect tool wear regularly; never continue cutting with damaged tools.