A corded hammer drill next to a drill bit and a chuck key

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

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

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

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

References

  1. ↑ "Definition of percussion drill in English". Oxford Dictionaries. Oxford University Press. Archived from the original on September 8, 2018. Retrieved September 8, 2018.
  2. ↑ "Impact drill". DIY Knowledge. Archived from the original on September 8, 2018. Retrieved September 8, 2018.
  3. ↑ "Cordless Hammer Driver Drill XPH11 Instruction Manual" (PDF). Makita. p. 2. Archived (PDF) from the original on 15 April 2018. Retrieved 15 April 2018. Blows per minute. High (2): 0 - 25,500 /min; Low: 0 - 7,500 /min
  4. ↑ "Drills Drilling Speed Test Results - DIY Gear Reviews". 2023-10-03. Retrieved 2023-10-23.
  5. ↑ Akku Schlagbohrschrauber
  6. ↑ Smil, Vaclav (2006). Transforming the Twentieth Century: Technical Innovations and Their Consequences. Oxford University Press (published April 4, 2006). ISBN 978-0195168754.
  7. ↑ Smil, Vaclav (2010). Why America Is Not a New Rome. The MIT Press. pp. 96. ISBN 978-0262195935.
  8. ↑ Weissenbacher, Manfred (2009). Sources of Power: How Energy Forges Human History by Manfred Weissenbacher. Praeger. p. 362.
  9. ↑ Iron in China
  10. ↑ Han, Gang; Dusseault, Maurice B.; Detournay, Emmanuel; Thomson, Bradley J.; Zacny, Kris (2009). "2". Principles of Drilling and Excavation (PDF). Wiley (published August 31, 2009). p. 60. Archived from the original (PDF) on July 13, 2019.
  11. ↑ "Cable Tool Drilling". Seismic Water Finder.
  12. ↑ Manning, John C. (1996). Applied Principles of Hydrology. Prentice Hall. p. 250. ISBN 978-0135655320.
  13. ↑ "Cable Tool Drilling". Seismic Water Finder.
  14. ↑ "History of Milwaukee". Milwaukee Tool. Retrieved 17 February 2014.
  15. ↑ "Hammer drill hand powered drill working example 70 yrs old!". YouTube.
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