The Rotary Hammer: Complete Guide

What is a rotary hammer?

A rotary hammer — also called a roto-hammer, rotary hammer drill, or demolition hammer — is a power tool designed to drill into hard, brittle materials such as concrete, masonry, stone, and brick. Unlike a standard drill that simply rotates a bit, a rotary hammer adds a powerful, pneumatic hammering action along the drill axis. This combination of rotation and percussive force breaks up the material ahead of the bit, making it dramatically more effective for tough substrates.

How it works: the piston mechanism

The defining feature of a rotary hammer is its electropneumatic drive system. A motor drives a piston inside an air cylinder. As the piston moves forward, it compresses air, which propels a striker forward at high speed to impact the bit — this is called an air-cushion or floating piston mechanism. The striker hits a special intermediate piece that transfers the blow to the bit. Because the impact is delivered via an air cushion rather than direct mechanical contact, the tool runs more smoothly and puts less strain on the user’s hands and wrists than a standard hammer drill.

The three operating modes available on most rotary hammers reflect this design:

Rotary only

Standard drilling in wood, metal, or plastic with no hammering. Ideal for general-purpose use.

Rotary + hammer

Combined rotation and percussion — the primary mode for drilling into concrete, stone, and masonry.

Hammer only (chiselling)

The bit is locked from rotating and delivers pure impact. Used for chipping, breaking tiles, or light demolition.

SDS chucks and bit systems

Rotary hammers use a specialised bit-retention system called SDS (from the German Steckdrehsystem, or “insert-twist system”). SDS bits have grooves that lock into the chuck and allow the bit to slide axially, which is essential so the hammering mechanism can move the bit independently of the chuck. Three main variants exist:

SDS-Plus	10 mm	Light to medium rotary hammers; most common for tradespeople and DIY
SDS-Max	18 mm	Heavy-duty demolition and large-diameter coring work
SDS-Quick	Various	Compact hammers; accepts both standard round-shank bits and SDS bits via adapter

Rotary hammer vs. hammer drill

These two tools are often confused. A hammer drill produces impact through direct cam-on-cam mechanical contact — essentially two toothed discs that click against each other. This delivers far less impact energy (measured in joules) and causes significantly more vibration transmitted to the hand. A rotary hammer’s pneumatic mechanism generates far greater impact energy with less user fatigue, making it the correct choice for masonry work beyond the lightest occasional tasks.

As a rough guide: use a hammer drill for occasional light-duty holes in brick; use a rotary hammer for anything in reinforced concrete, regular masonry work, or holes larger than about 13 mm.

Common applications

Drilling anchor holes in concrete

Installing rebar and post-anchors

Cutting channels for conduit & pipes

Removing tiles and floor adhesive

Coring holes for plumbing and HVAC

Light demolition and chipping work

Key safety considerations

Rotary hammers are powerful tools and demand proper precautions:

• Dust control — concrete dust contains silica, a known carcinogen. Use vacuum extraction attachments or a wet drilling system, and always wear an FFP2/N95 or higher respirator.
• Eye and ear protection — flying debris is common; impact noise can exceed 100 dB. Use safety glasses and hearing protection.
• Rebar detection — always scan the work surface with a rebar detector (cover meter) before drilling to avoid hitting embedded steel, which can cause severe kickback.
• Anti-vibration — long-term use without vibration-dampening handles can cause hand-arm vibration syndrome (HAVS). Use tools with AVS systems and observe daily exposure limits.
• Firm grip and stance — use the auxiliary side handle always. Bit jamming can cause violent tool rotation. Keep a firm, two-handed grip.

Choosing the right rotary hammer

The most important specification is impact energy in joules. For light trade work (drilling up to 25 mm holes), a 1.5–3 J SDS-Plus tool is sufficient. Medium-duty work — anchor installation, regular concrete drilling up to 40 mm — calls for 3–8 J. Heavy demolition and large-diameter coring requires an SDS-Max tool with 8–20 J or more. Cordless models on modern high-voltage platforms (36 V / 40 V) now approach corded performance for most trade applications, offering greater freedom of movement on site.