BANKA hand drill
In the early days of systematic prospecting for alluvial tin ore on the isle of Bangka (Indonesia) the Dutch mining-engineer J.E.Akkeringa, who was working there, designed a set of very ingenious and sturdy hand drilling tools. The great value of this method of tin exploration was gradually recognized and by the end of the 19th century,the original manufacturers of the "Banka hand drill", started its production for world-wide sale.
Fields of application:
As long as there are still inhospitable and isolated areas in the world, the Banka will be indispensable for the prospection of:
The Banka drill will penetrate shale, soft slate, hard cemented gravel
and weathered decomposed bedrock, but is not suitable for drilling in hard rock.
By working with casings, the most valuable information can be obtained from
the bore hole. High ground water level or shallow water (swamps, river-beds
and rivers or estuaries) stress the practical excellence of this simple drill.
The Banka can be transported in "one man packs" for operation anywhere.
The drill can be supplied in two versions: Size 4 (4-inch) and Size 6 (6-inch). Size 4 is mostly used for scout prospecting; Size 6 for the evaluation of low grade placers and/or coarse grains (gold - diamond).
Although in grounds, which are easy to penetrate, depths of more than 40 m have been reached with Size 4. There is a growing tendency to employ so-called telescopic boring (Size 4 casing passing through Size 6). The outside diameter of the external flush casing for Size 4 is 121 mm, and for Size 6 it is 165 mm.
Place a casing, fitted with a casing shoe, in a shallow hole in the ground, fit the working platform for the four drillers on top of the casing, which is then rotated slowly by another two to four men. In this way the casing is forced down by a combination of the weight of the platform, and the four drillers, the jerking movement of the drilling tool, and the reduction of friction resulting from the rotation of the casing.
The cylindrical column of soil cut off by the casing shoe is taken out with a bailer, which is screwed to the end of drill rods.
The casing string should sink more or less simultaneously with the emptying of the bore hole.
For the investigation of alluvial ore deposits no drilling should be done under the casing shoe. The casing should actually sink ahead at least 6 to 10 cm and in this way a sample is obtained by the Banka outfit, which - with respect to quantity and quality - cannot be obtained by any other simple drilling method.
This alluvial gold placer was explored with 4-inch manual Banka drill. Estimated reserves were less than 5% below real mining production.
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