If the cores are not obtained from the field, samples obtained by rough cutting are cored with thin wall diamond rotary bits which may be detachable or, more commonly, integral to the core barrel.
The usual size range for laboratory core drills is from 152.4 mm (6in.) diameter down to 19.5 mm (0.75in.). Table 1.1 gives available core sizes.
Almost any kind of drill can be adapted for rock work, but a heavy rigid machine is desirable in order to assure consistent production of high quality core. The work block must be tightly clamped to a strong base or table by at least two steel straps so as to prevent any tilting, oscillation or other shifting. To avoid unnecessary unclamping and rearrangement of the work block, it is desirable to have provision for traversing the drill head or the work block. Traversing devices must lock securely to eliminate any play between the drill and work. The drill travel should sufficient to permit continuous runs of at least 152.4 mm (6in.) and preferable of 254-304.8 mm (10-12in.) without need for stopping the machine. Finally, the drill should have some provision of automatic feed.
If the cores are not obtained from the field, samples obtained by rough cutting are cored with thin wall diamond rotary bits which may be detachable or, more commonly, integral to the core barrel.
The usual size range for laboratory core drills is from 152.4 mm (6in.) diameter down to 19.5 mm (0.75in.). Table 1.1 gives available core sizes.
Almost any kind of drill can be adapted for rock work, but a heavy rigid machine is desirable in order to assure consistent production of high quality core. The work block must be tightly clamped to a strong base or table by at least two steel straps so as to prevent any tilting, oscillation or other shifting. To avoid unnecessary unclamping and rearrangement of the work block, it is desirable to have provision for traversing the drill head or the work block. Traversing devices must lock securely to eliminate any play between the drill and work. The drill travel should sufficient to permit continuous runs of at least 152.4 mm (6in.) and preferable of 254-304.8 mm (10-12in.) without need for stopping the machine. Finally, the drill should have some provision of automatic feed.
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