Milling Teeth Performance Depends on Material, Drum Design, and Carbide Composition

[MikePhua]

Evolution of Road Milling Teeth
Road milling teeth, also known as cutting bits or picks, are critical components mounted on rotating drums of cold planers and reclaimers. These tungsten carbide-tipped tools are responsible for grinding asphalt and concrete surfaces during resurfacing operations. Over the past three decades, manufacturers like Wirtgen, Kennametal, Sandvik, and Everpads have developed a wide range of tooth profiles to suit different materials, depths, and machine speeds.
The most common tooth types include W-series (W6, W7, W8), RZ-series, Tri-spec, and RoadRazor ECO. Each has unique geometry, body diameter, and carbide tip configuration. The choice of tooth directly affects wear rate, cutting efficiency, and fuel consumption.
Material Conditions Shape Tooth Longevity
Operators consistently report that the type of material being milled—not the brand of tooth—is the dominant factor in wear. For example:

• Superpave asphalt mixes with high silica content can burn through teeth in under 7,000 square yards
  
• River gravel-based asphalt is notorious for rapid wear due to its hardness and angularity
  
• Temporary lane asphalt on highways like I-95 has shown better wear performance, even at depths over 8 inches
  

In one case, a crew in Daytona Beach switched from Wirtgen W6 teeth to Kennametal RZ16 after experiencing premature burnout before noon. The change restored full-day performance, suggesting that tooth selection must be tailored to local aggregate conditions.
Drum Design and Tooth Rotation Matter
Tooth wear is also influenced by drum configuration, including:

• Angle of attack: Optimal cutting occurs around 42–45 degrees, skewed 7–8 degrees toward the drum center
  
• Tooth rotation: Proper rotation prevents flat spots and uneven wear. Water spray should target the front of the tooth to aid rotation
  
• Drum evacuation efficiency: Drums that clear millings quickly reduce recirculation and heat buildup. A small surge pile at the rear of the drum indicates good design
  

Switching from a weld-on drum to a Keystone quick-change system has been shown to improve tooth life by up to 30%, due to better holder alignment and easier maintenance.
Carbide Composition and Manufacturing Variability
Most milling teeth use recycled carbide, a byproduct of other industrial processes. This introduces variability in cobalt content, which affects hardness and toughness:

• Low cobalt: Harder tips that resist wear but are prone to breakage
  
• High cobalt: Softer tips that wear faster but resist fracture
  

Body wash—where the steel body erodes before the carbide is spent—is a common failure mode. Manufacturers like Sandvik have addressed this with double-carbide designs and reinforced bodies, such as the Tri-spec teeth used successfully on Interstate 94.
Field Strategies to Extend Tooth Life
Operators have developed several techniques to maximize tooth performance:

• Spraying water ahead of the cut to cool the drum and reduce friction
  
• Monitoring surge piles to assess drum evacuation
  
• Changing teeth mid-shift when wear accelerates due to unexpected material hardness
  
• Using edge cutters with proper water coverage to prevent asphalt buildup on drum sides
  

In one crew, changing a full drum of W7 teeth took just 20 minutes, with workers moving like a NASCAR pit team to keep trucks rolling.
Conclusion
The performance of milling teeth is a complex interplay of material properties, drum design, carbide chemistry, and operational technique. While brand loyalty plays a role, experienced operators know that adapting to local conditions and maintaining equipment properly are the keys to maximizing productivity and minimizing downtime. Whether cutting 2 inches or 6, the right tooth in the right place makes all the difference.