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Two questions come up regularly among operators and contractors working with hydraulic breakers, one about what goes on a job site before the machine starts, the other about what happens when it stops working as expected. The first is about tool selection: which chisel do I fit for this material?
Choosing the right chisel before the job starts saves time and repair costs.
Chisel selection is one of the most straightforward ways to improve breaking output, and one of the most overlooked. A site running a single moil point on every job is leaving efficiency on the table. The three standard tool geometries each have a distinct working principle, and using the right one for the material can cut the number of blows per tonne significantly.
Moil point for hard, brittle materials
The moil point has a tapered, conical tip. Its purpose is to concentrate the full impact energy of the piston into the smallest possible contact area, generating extreme point loads that initiate fractures in dense materials.
This is the right tool for granite, basalt, hard limestone, heavily reinforced concrete, and quarry rock. Anywhere the goal is to crack and fragment a hard mass, the moil point is the starting choice. It works by creating fracture networks that propagate through the material, the more brittle the rock, the more effective the geometry.
The flat chisel distributes impact load across a wider blade face rather than a single point. This reduces peak contact stress but makes the tool highly effective at exploiting existing planes of weakness, construction joints, pour lines, bedding planes in sedimentary rock, and the natural layering in brick or block.
For concrete demolition, particularly slabs and pavements, the flat chisel aligned with a joint or crack will break the material in a fraction of the blows a moil point would require. The same logic applies to asphalt, softer stone, and any material where a splitting action is more efficient than fracture initiation.
A practical test: if a moil point is skipping or skating across the surface without biting, the material may respond better to a flat chisel applied along a visible fracture line or edge.
The blunt tool transfers impact energy as a compressive face load rather than penetration. It does not break material in the conventional sense, it drives or compacts it.
Primary applications are driving steel sheet piles, anchor rods, and timber posts, as well as compacting granular fill in confined areas where a plate compactor cannot reach. It is also used for secondary breaking, pressing already-fractured fragments down rather than splitting them further.
One important note: pile driving with a hydraulic breaker requires careful alignment. The blunt tool must strike the pile head square and vertically, any offset load during driving deflects the pile and applies lateral force to the breaker in the same way as using the chisel as a lever. Always use a proper driving cap or helmet on the pile head.
The right chisel for the job needs to be decided before the machine starts, not after something goes wrong. A flat chisel fitted the night before a concrete demolition job costs nothing.
ESTM hydraulic breakers are built with a three-component internal design, HARDOX steel housing, and an anti-blank firing system that protects the machine during normal operation. Protecting that investment comes down to the configuration choices made before the work begins.
Contact the STM Europa team for guidance on chisel selection, underwater kits, or matching the right ESTM breaker to your application.