Rotary hammers are heavy duty tools designed to bore holes in concrete and rock.

They consist of a normal high powered drill machine with a main shaft that fits in an airtight cylinder. The other end of the cylinder has a piston which is moved back and forth several times a second by complex mechanical gearing. The rapid pumping of the air in the cylinder causes the bit to hammer its way through the material being drilled.
Since the force of impact is delivered by air, they are sometimes known as electro-pneumatic drills.
Some models have an option to disengage the rotation of the shaft and lock it in one position. This allows the drill to be used for chipping and breaking when fitted with a chisel shaped bit.
The drill bits for rotary hammers are not usually held in chucks but use a system developed by Bosch known as SDS or SDS-Max . They are tipped with tungsten carbide tips and have a very long life.

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