Cutting Picks: The "Sharp Teeth" of Mining and Tunneling

Deep underground, in coal mines and rock tunnels, a simple tool takes the most brutal punishment. It strikes coal and rock head-on, wearing itself down with every rotation and every impact. That tool is the Cutting pick — often called the "teeth" of heavy machinery. Whether on a shearer drum in a coal mine or on the cutter head of a tunnel boring machine, cutting picks are the most critical and most basic consumable component. Their performance directly determines equipment efficiency, energy consumption, and operating cost.

This article explains cutting picks in six parts: structure, core materials, manufacturing, classification and selection, failure modes, and industry trends.

Structure: The Steel Body and Carbide Tip

A typical cutting pick looks simple but is precisely engineered. It has two main parts: a high-strength alloy steel body (the shank and head) and a cemented carbide tip at the top.

The steel body acts as the backbone. It takes huge impact and torsional forces from the cutting machine, plus constant abrasion from rock chips. The material must have high strength, high toughness, and proper surface hardness.

Common materials include 35CrMo and 42CrMo — high-quality alloy steels with good hardenability and fatigue resistance. Modern high-end picks use cold forging instead of traditional machining. A large press shapes the steel bar in one stroke. This keeps the metal grain flow continuous and dense, significantly improving fatigue strength.

After forging, the body undergoes vacuum heat treatment. Unlike conventional heat treatment, vacuum processing prevents surface oxidation and decarburization, producing a uniform tempered martensite or bainite structure. The final surface hardness is typically controlled between 38–45 HRC. This range is optimized by long experience: harder means more brittle and prone to fracture; softer means faster wear, leading to early carbide tip loss.

The cemented carbide tip is the actual rock-breaking element. It is made by sintering tungsten carbide (WC) powder with a binder metal — usually cobalt (Co) — using powder metallurgy. Tungsten carbide provides extreme hardness (about HV 1600–2000). Cobalt provides toughness.

In coal and rock engineering, YG11C is one of the most widely used carbide grades. "YG" stands for tungsten-cobalt carbide. "11" indicates about 11% cobalt by weight. "C" typically means coarse tungsten carbide grains, which improve impact resistance. Typical properties of YG11C:

For harder, more abrasive rock, lower cobalt grades (8–10%) or grades with added rare metal carbides (TaC, NbC) are used to increase wear resistance.

Welding and Wear Layer: The Key to Long Life

The carbide tip is not simply pressed into the steel body. It is joined by specialized welding — usually high-frequency induction brazing or furnace brazing. A brazing filler metal (copper-based or silver-based) is placed between the tip and the socket, heated until it melts, and then cooled to form a strong metallurgical bond.

Even more important is the high-hardness wear-resistant layer formed around the weld — typically on the end face of the pick head. This layer is applied by hardfacing or cladding and can reach 55–65 HRC — much harder than the steel body. The wear layer does three things:

• Protects the weld from direct abrasion by rock chips.

• Acts as a "backup cutting edge" as the carbide tip gradually wears, extending overall pick life.

• Helps prevent the carbide tip from being knocked off by impact.

Field data shows that picks with a high-quality wear layer last 30–50% longer than picks without one.

Classification: A Full Product Line for Different Conditions

Cutting picks are divided into three main categories based on the equipment and working conditions:

Shearer picks are mounted on the drum of a longwall shearer. They rotate with the drum to cut the coal face. They have longer bodies and larger shank diameters (typically 30–38 mm) to handle high torque and high impact. For soft coal, standard picks are used. For hard coal or coal with rock bands, heavy-duty picks are required. A typical shearer drum carries 100–200 picks. Failure of a single pick can disrupt production.

Roadheader picks are used on the cutting head of roadheaders — both boom-type and full-face machines. These picks must handle everything from soft coal to hard rock. Their tip shapes and body designs are more varied. Common types include point-attack picks (conical) for high-impact conditions and radial picks (flat-shaped) for softer rock or coal where cutting dominates.

Rotary drilling picks are used on the drilling buckets or core barrels of rotary drilling rigs — mainly in foundation engineering and shoring. These picks encounter soil, gravel, cobbles, and even weathered rock. They have shorter bodies and sharper, more pointed carbide tips for efficient penetration in loose and semi-loose ground. They are often used with a holder and sleeve system for quick field replacement.

Beyond these three, there are also milling picks for road planers and trenching picks for trenchers.

Selection Rules: Rock Conditions Come First

There is no "one-size-fits-all" cutting pick. Selection must match the actual working conditions. Key factors include rock hardness, abrasiveness, and fracture development.

Note: f = Protodyakonov rock hardness coefficient.

Pick consumption is a key economic indicator. In a longwall coal face with medium-hard coal (f ≈ 3), consumption is about 10–30 picks per 10,000 tons of coal mined. In hard rock tunneling, consumption can reach 2–5 picks per cubic meter of rock excavated.

Failure Modes: Know Your Enemy

Pick failure is inevitable. But understanding how they fail helps optimize selection and usage.

Carbide tip wear is the ideal failure mode. The tip gradually becomes blunt, cutting efficiency drops, and the pick needs replacement. In normal wear, the tip height decreases evenly, and the wear layer on the body end face wears down at the same time.

Carbide tip loss is the most common and most troublesome premature failure. Causes include poor brazing (voids or lack of fusion in the weld), poor wear layer quality, rapid steel body wear that leaves the tip unsupported, or sudden heavy impacts from faults or hard inclusions. A pick that loses its tip is scrap. Worse, the loose carbide fragment can damage other picks or the conveying system.

Steel body fracture usually comes from material defects, improper heat treatment, or excessive impact loads. Fractures most often occur at the transition radius between the shank and the head — a stress concentration point.

Excessive steel body wear happens when body hardness is insufficient or the wear layer fails. The body wears into a "mushroom" shape, and the carbide tip eventually falls off because it is no longer held securely.

Carbide tip chipping or cracking occurs in very hard, brittle rock if the tip lacks enough toughness. In such conditions, a higher-cobalt, coarser-grain carbide grade is needed.

Trends and Innovation

As mining and tunneling equipment becomes larger, more intelligent, and greener, cutting pick technology continues to evolve.

New carbide materials — The traditional WC-Co system is being refined. Adding grain inhibitors like Cr3C2, VC, or TaC produces ultra-fine grain carbides (grain size < 0.5 μm), which improve transverse rupture strength while maintaining hardness. Gradient carbides (cobalt-rich on the surface, cobalt-poor inside) are also under development.

Coatings and surface treatment — Beyond hardfacing, some high-end picks now use PVD or CVD coatings such as TiN, TiAlN, or AlCrN. These coatings have hardness of 2000–3500 HV and thickness of only 2–10 μm, but they significantly reduce friction and adhesion.

Biomimetic and optimized design — Pick shapes inspired by pangolin claws or beetle shells are being tested. Finite element analysis (FEA) is widely used to reduce stress concentrations.

Smart monitoring and prediction — On large roadheaders, monitoring cutting motor current and vibration signals can indirectly estimate pick wear, enabling condition-based replacement instead of fixed schedules.

Remanufacturing and recycling — Worn picks can be rebuilt by hardfacing or replacing the carbide tip. A remanufactured pick typically costs 40–60% of a new one and lasts 80% or more as long. This fits circular economy and green manufacturing principles.

The global Cutting pick market was about $1.8 billion in 2023 and is projected to reach $2.5 billion by 2030, growing at about 4.2% annually. China — the world's largest coal producer and a major tunneling market — accounts for 35–40% of global consumption.

The Bottom Line

Cutting picks are small, but they are the indispensable "sharp teeth" of mining and tunneling. From cold-forged and vacuum heat-treated steel bodies, to precisely formulated carbide tips and strong brazed joints, to cleverly designed wear layers — every pick embodies materials science, metallurgy, and mechanical engineering. Understanding their structure, materials, classification, and failure modes helps engineers select and use them wisely — cutting energy use, raising efficiency, and controlling costs. With new materials and new technologies emerging, this old consumable tool is gaining new life.