Power tool

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A hammer drill, also known as a percussion drill or impact drill, is a power tool used chiefly for drilling in hard materials.[1][2] It is a type of rotary drill with an impact mechanism that generates a hammering motion. The percussive mechanism provides a rapid succession of short hammer thrusts to pulverize the material to be bored, so as to provide quicker drilling with less effort. If a hammer drill's impact mechanism can be switched off, the tool can be used like a conventional drill to also perform tasks such as screwdriving.

Function

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Hammer drills have a cam-action or percussion hammering mechanism, in which two sets of toothed gears mechanically interact with each other to hammer while rotating the drill bit. With cam-action drills, the chuck has a mechanism whereby the entire chuck and bit move forward and backward on the axis of rotation.

This type of drill is often used with or without the hammer action, but it is not possible to use the hammer action alone as it is the rotation over the cams which causes the hammer motion. A hammer drill has a specially designed clutch that allows it to not only spin the drill bit, but also to punch it in and out (along the axis of the bit).

The actual distance the bit travels in and out and the force of its blow are both very small, and the hammering action is very rapid—thousands of "BPM" (blows per minute)[3] or "IPM" (impacts per minute). Although each blow is of relatively low force, these thousands of blows per minute are more than adequate to break up concrete or brick, using the masonry drill bit's carbide wedge to pulverize it for the spiral flutes to whisk away.

For this reason, a hammer drill drills much faster than a regular drill through concrete, brick, and thick lumber. In standardized drilling speed tests, the most effective hammer drills improve drilling speeds by upwards of 30% compared to completing the same task with the hammer mode disabled.[4] Hammer drills are increasingly powered by cordless technology.

Use

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Holes in hard materials are needed for anchor bolts, concrete screws and wall plugs. Hammer drills are not typically used for production construction drilling, but rather for occasional drilling of holes into concrete, masonry or stone. They are also used to drill holes in concrete footings to pin concrete wall forms and to drill holes in concrete floors to pin wall framing. SDS rotary drills are more commonly used as dedicated masonry drilling tools in construction.

Hammer drills almost always have a lever or switch that locks off the special "hammer clutch," turning the tool into a conventional drill for wood or metal work. Hammer drills are more expensive and more bulky than regular drills, but are preferable for applications where the material to be drilled—concrete block or wood studs—is unknown. For example, an electrician mounting an electrical box to a wall would be able to use the same hammer drill to drill into either wood studs (hammer disabled) or masonry walls (hammer enabled).

History

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Ancient China's principal drilling technique,[5] percussive drilling, was invented during the Han dynasty. The process involved two to six men jumping on a lever at rhythmic intervals to raise a heavy iron bit attached to long bamboo cables from a bamboo derrick.[6][7][8] Utilizing cast iron bits[9] and tools constructed of bamboo, the early Chinese were able to use percussion drilling to drill holes to a depth of 3,000 ft (910 m). The construction of large wells took more than two to three generations of workers to complete.[10] The cable tool drilling machines developed by the early Chinese involved raising and dropping a heavy string of drilling tools to crush through rocks into diminutive fragments.[11] In addition, the Chinese also used a cutting head secured to bamboo rods to drill to depths of 915 m (3,002 ft).[12] The raising and dropping of the bamboo drill strings allowed the drilling machine to penetrate less dense and unconsolidated rock formations.[13]

The origin of the first hammer drill is a matter of contention. German company Fein patented a Bohrmaschine mit elektro-pneumatischem Schlagwerk ("drill with electro-pneumatic striking mechanism") in 1914. German company Bosch produced the first "Bosch-Hammer" around 1932 in mass production. The US company Milwaukee Electric Tool Corporation states that in 1935, it was selling a lightweight 1⁄4 in (6.4 mm) electric hammer drill (cam-action).[14]

Hand-cranked percussion drills were made in the UK in the mid-twentieth century.[15]

See also

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References

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A Brief History of the Hammer Drill

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Perhaps the most important difference between humans and the rest of the animal world is our ability to make and use tools. Tools have enabled us to perform tasks that would otherwise be difficult or impossible to accomplish. The drill is a perfect example of this.

Without a drill, we would have difficulty drilling a hole in a material like wood, let alone harder materials like concrete or steel, not that concrete and steel would even exist without the use of other tools, but that’s another topic I won’t cover here.

If we trace the history of the drill, we come to the ancient Egyptians and Harappans, who used a device called the bow drill, which was used more for making fire, but was also used for rudimentary woodwork. It was also used by the ancient equivalent of the modern dentist, the idea of which would surely raise the heartbeat of anyone with a phobia of dental treatment.

The components of this device are the bearing block, the spindle, the fireboard and the bow. The string of the bow is wrapped around the spindle, which is held at one end by the bearing block and at the drilling end by the fireboard. Leverage is given to the user of this device by the string attached to the bow.

Another simple device that has been used for hundreds of years is the pump drill. The components of this device are the drill shaft, a heavy flywheel, a narrow piece of board with a hole in the center, and a string. The flywheel is attached to the lower end of the shaft, and the board is slipped over the upper end of the shaft using the hole. The string is put through a hole in the top of the shaft and attached to both ends of the board.

At the end of the shaft is a hole into which the bits are inserted. The board is then held in place while the shaft is rotated until the board has lifted almost to the top of the shaft and the string is wrapped tightly around the shaft. The tip of the shaft is placed on the material to be drilled, and pressure is applied to the board. The shaft spins rapidly, and when the board reaches the bottom of the shaft, it is allowed to bounce back so that the string wraps around the shaft again, and drilling can begin anew.

A more familiar device is the clamp and drill, a drill with a u-shaped handle. The user applies pressure to the top of the drill with one hand and can use the other hand to make a twisting motion over the u-shaped handle.

The U-shaped handle can be considered as a kind of crankshaft that offers higher torque but lower rotational speed compared to other hand drills. Another tool from the not-too-distant past is the old hand drill, which looks like an eggbeater and has a handle on one side that you can hold with one hand, and a rotating device with a handle on the other side that provides the drilling momentum.

Craftsmen from earlier times would be surprised at how easy it is to do drilling work with modern electric drills compared to their primitive counterparts. There are many types of drills in use today, most with pistol grips, and there are variations on the standard electric drill, such as the hammer drill, which has a hammer action that allows it to drill into masonry.

The percussion function can be turned off when not needed. A more powerful drill is the hammer drill, which combines the percussive mechanism with the rotary mechanism.

Cordless drills offer a degree of independence from the need to be near an electrical outlet. While in the past these drills had the disadvantage of relying on batteries that needed to be recharged regularly and had a relatively short lifespan, battery technology has improved greatly in recent times, making cordless drills a more versatile option.

Perhaps in a hundred years, drilling technology will be so advanced that our current technology will seem as primitive to future generations as the bow drill did to us. For more information please click here.

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