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A rotary hammer, also called rotary hammer drill is a
power tool A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labor used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed ...
that can perform heavy-duty tasks such as
drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driverchuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to ...
ing and
chisel A chisel is a tool with a characteristically shaped cutting edge (such that wood chisels have lent part of their name to a particular Grind#Typical grinds, grind) of blade on its end, for carving or cutting a hard material such as wood, Rock (g ...
ing hard materials. It is similar to a
hammer drill A hammer drill, also known as a percussion drill or impact drill, is a power tool used chiefly for drilling in hard materials. It is a type of rotary drill with an impact mechanism that generates a hammering motion. The percussive mechanism provid ...
in that it also pounds the drill bit in and out while it is spinning. However, rotary hammers use a
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...
mechanism instead of a special
clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
. This causes them to deliver a much more powerful hammer blow, making it possible to drill bigger holes much faster. Most rotary hammers have three settings: drill mode, hammer drill or just hammer, so they can act as a mini
jackhammer A jackhammer (pneumatic drill or demolition hammer in British English) is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel. It was invented by William Mcreavy, who then sold the patent to Charles Brady Kin ...
.


Function

Compared to less advanced power units known as
hammer drill A hammer drill, also known as a percussion drill or impact drill, is a power tool used chiefly for drilling in hard materials. It is a type of rotary drill with an impact mechanism that generates a hammering motion. The percussive mechanism provid ...
s, rotary hammers tend to be larger and provide a bigger impact force by utilizing a technology called the "electro-pneumatic" (EP) hammering mechanism, because it is powered directly by electricity instead of a separate air compressor. Rotary hammers have two pistons – a drive piston, and a flying piston. An electric motor turns a crank, which moves the drive piston back and forth in a cylinder. The flying piston is at the other end of the same cylinder. The pistons do not actually touch, but the air pressure in the EP cylinder allows for a much more efficient transfer of hammering energy than springs in the cam-action style hammer drills. The majority of modern rotary hammers as well as all electric-powered chipping guns or jack-hammers all utilize this EP technology. Modern units allow the hammer and rotation functions to be used separately or in combination, i.e., hammer mode, drill mode, or both. When used in the hammer mode, the tool provides a drilling function similar to a
jackhammer A jackhammer (pneumatic drill or demolition hammer in British English) is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel. It was invented by William Mcreavy, who then sold the patent to Charles Brady Kin ...
. Rotary hammer drills have an oil filled gearbox, which allows them to operate durably despite the large forces and shocks they receive and the grit-filled environments where they are often used. The type of work they do means that they require a "slip-clutch" which engages when the drill bit jams and sufficient torque is put onto the "slip-clutch" mechanism. This stops the violent wrenching motion that a drill without a clutch would cause when stopped suddenly from full speed, protecting the drill from damage. The slip-clutch also protects the operator, but does not always prevent injury. Some manufacturers have introduced additional technology to protect the operator. Hilti has a technology called "ATC" or "Active Torque Control" which works by disengaging the drive from the motor when the tool body begins to rotate excessively through the action of a secondary magnetic clutch in addition to the standard slip-clutch. DeWALT has a related system called "CTC" or "Complete Torque Control" which utilizes a two-position slip-clutch so that the operator can select the lower torque setting for greater safety. A number of "special shanks" have been developed by various manufacturers. Over the years a fair number of these proprietary systems evolved, but the remaining shanks in use today are: SDS+, SDS-MAX, and SPLINE SHANK. These shanks were developed in order to allow for the bit to "slide" back and forth while rotating, so that the drill bit can efficiently transfer the force of the electro-pneumatic hammering mechanism to the working surface.


Use

Rotary hammers can be used for "doweling" (repetitive drilling of large rebar anchor holes), and drilling through-holes in concrete and masonry walls. The hammering action helps break up the masonry so that it can be removed by the
drill bit Drill bits are cutting tools used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order ...
's flutes. Apart from their main function of drilling concrete, the rotary action can be switched off and use is made of just the percussive force. Chisel and point accessories are used for small chipping jobs.


Special chuck

Rotary hammers have such force that the usual masonry bits are no longer adequate. Their smooth shanks would be pounded loose from the tool's chuck in a few seconds. Rotary hammers require special bits with an SDS shank (which can stand for Slotted Drive Shaft or Special Direct System), which locks into the rotary hammer without the need for a chuck. The hammer strikes the drill directly, instead of a chuck holding the drill.


Jams

Jams are most often caused by hitting
reinforcing steel Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. ...
or by a worn bit. In both cases the drill must be disengaged from the bit and the jammed bit backed out of the hole with vise grips or monkey wrench. Some bits utilize a full carbide "four-cutter" head with a geometry that makes jamming less common - even when rebar is present. These full-carbide "four-cutter" bits can even, in some instances, drill through rebar, although this should be done with caution. A worn drill bit will still drill a horizontal hole, although of a slightly smaller diameter than one created when it was new. When a drill like this is used to drill holes down into a concrete slab, the flutes are so worn that they can no longer lift the dust out of the hole; the concrete dust packs up in the hole and jams the bit.


History

Company
Hilti Hilti Corporation (Hilti Aktiengesellschaft or Hilti AG, also known as Hilti Group) is a Liechtensteiner multinational company that develops, manufactures, and markets products for the construction, building maintenance, energy and manufactu ...
had the first "electro-pneumatic" rotary hammer on the market in 1967, the Hilti TE 17


Types

The perforating devices differ, basically, depending on the intended use, which leads to the appropriate size, weight and impact force when applied: * Relatively light electric punches (less than 10 kg) are prevalent in the construction field and the DIY market. * Pneumatic perforators are used in mining industry and highway construction. * Hydraulic hammers demonstrate the highest performance and weight (150 kg or more). Operation of perforating equipment is associated with much noise. Only in the last 20 years it became possible to decrease the noise level to about 100 dB(A); earlier levels over 125 dB(A) were common.


References


External links


How's It Work? Rotary Hammers
interview with Trey Sklar at protoolreviews.com
How To Drill Into Bricks with Hammers
Easy Steps {{Power tools Hand-held power tools