[[Image:icon_stonehammer.png|right|80px]]
[[Image:Stone_hammer drilling.jpg|thumb|right|200px|The Stone-hammer in India, drilling a 20 m deep well in a stony layer. Photo: Netherlands Water Partnership.]]
[[Image:Stone hammer drilling in action.jpg|thumb|right|200px|Stone hammer drilling in action]]
[[Image:Emptying the drill bit.jpg|thumb|right|200px|Emptying the drill bit]]
[[Image:percussion gouge.jpg|thumb|right|200px|percussion gouge]]
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The Stone Hammer is a form of [[Percussion - general|percussion drilling]], used when boulders or hard clay is encountered. A hollow drill bit is attached to a hammering tool. The hammering tool consists of a heavy weight which moves up and down in a pipe. Once the bit and hammering tool are lowered into the borehole by a cable, the same cable can be used to do the hammering. Lifting and dropping the hammer drives the drill bit down. When 60cm has been drilled, the unit is pulled up to the surface to empty the hollow drill bit. The stone hammer is only successful when boulders are encountered, not in homogeneous or solid stone layers were displacement of the material is not possible.
The Stone-hammer method has won a competition for innovative irrigation technologies organized by the World Bank, Winrock and International Development Enterprises (IDE).
===Suitable conditions===
Percussion drilling is suitable for unconsolidated and consolidated formations: Sand, silt, stiff clays, sandstone, laterite and gravel layers.
* Less risk of contamination of the water.
===Construction, operations and maintenance===
Equipment is commercially produced in western countries. Local production is possible. Percussion drilling is hard work. Use of a small engine may be appropriate.
===Costs===
The costs are 20-60% less then those of hand dug wells.
The cost of introduction are between US$ 15,000 - 30,000 per project, including a production drill set, drawings, hands-on training, and the first wells.
===Field experiences===
The stone hammer is mainly used in India and Nicaragua, and sometimes in Madagascar.
The percussion gouge is mainly used in western countries.
"The Stone-hammer is slow but does not give us the headache of the cost and maintenance of motorized drilling rigs". A. Fajardo, Director of the Nicaraguan NGO Cesade .
===Manuals, videos and links===
* [http://www.practicafoundation.nl/wp-content/uploads/PDF/Practica%20drilling%20Rs%20versie%201th%20september%2005.pdf Rota-sludge and Stone Hammer drilling, part one: Drilling Manual] by Practica Foundation.
* [http://www.practicafoundation.nl/wp-content/uploads/PDF/practica-production-rs-versie-1th-september-051.pdf Rota-sludge and Stone Hammer drilling, part two: Production Manual] by Practica Foundation.
* [http://www.rural-water-supply.net/en/implementation/manual-drilling manual Hand Drilling Techniques.] Rural Water Supply Network. An analysis and comparison of all the drilling techniques, including 3 in-depth manuals of comparisons.
=== Acknowledgements===
* The basis for the material on this page was obtained from a desk study shortly to be published on the website of the [http://www.practicafoundation.nl/ Practica Foundation], and from the [http://www.rural-water-supply.net/ Rural Water Supply Network], and specifically its [http://www.rural-water-supply.net/en/implementation/manual-drilling manual drilling section].
* [http://www.lboro.ac.uk/well/resources/technical-briefs/43-simple-drilling-methods.pdf 43. Simple drilling methods.] WEDC.