cutterhead

A cutterhead is the rotating forward end of a tunnel boring machine (TBM) or other excavation equipment, equipped with replaceable cutting tools. Its primary function is to interact with rock or soil at the tunnel face, using cutting tools to break material so the machine can advance and remove the spoil.

In a TBM, the cutterhead is a large cylindrical or spherical structure integrated with the shield. It carries cutting tools such as disc cutters or picks mounted in hardened blocks on its surface. Carbide-tipped discs are common for breaking harder rock, while other tool arrangements may be used for softer ground. As the cutterhead spins, hydraulic or mechanical thrust pushes the machine forward against the ground, and the resulting fractured material, or muck, is removed through a conveyor system—typically a screw or belt conveyor—within the shield and carried out of the tunnel.

The cutterhead’s design and tool configuration are tuned to ground conditions. Hard-rock TBMs rely on robust disc cutters and higher thrust, while soft-ground or earth-pressure-balanced machines may employ different cutter arrangements and face-support systems to maintain stability during excavation. Cutterhead wear is a key maintenance concern; worn cutters reduce cutting efficiency and can require frequent replacement and inspection to prevent advances from stalling.

Cutterheads are central to modern mechanized tunneling and are used in a variety of tunnel types, including long highways, railways, and metro systems. They enable continuous excavation with integrated advance, muck removal, and, in many cases, ground stabilization features around the shield.

See also: tunnel boring machine, disc cutter, earth-pressure balance TBM, slurry TBM, continuous miner.