Wednesday, 17 April 2013

Impegration Depth

The term "impregnation depth" refers to the thickness of the diamond impregnated matrix layer on a core bit crown as shown in the illustration to the right. The variable “y” is used to define the impregnation depth dimension for a particular core bit.

IDP offers many sizes of core bits with standard impregnation depths of 6 mm (0.24 inch), 9 mm (0.35 inch) and 12 mm (0.47 inch). Other customer defined impregnation depths are available on request. Unless otherwise specified, a standard 9 mm impregnation depth is supplied for most North American sizes of core bits while a standard 6 mm impregnation depth is supplied for all thin-walled metric “I”, “T”, “TT”, “T2” and “T6”-series core bits.

As the price of an impregnated core bit increases from a 6 mm impregnation depth through to a 12 mm impregnation depth, consideration should be given to the economics of selecting a particular impregnation depth. While the initial cost of a core bit with a 6 mm depth of impregnation is relatively low, the expected overall bit life will also be lower than that of a bit with a thicker impregnation depth. For this reason, a 6 mm impregnation depth is generally recommended for use in shallow drill holes or for non-Wireline applications where more frequent bit changes are not objectionable. Conversely, the higher initial cost of a core bit with a 12 mm impregnation depth is largely offset by its inherently long bit life when used to drill extremely deep holes. The cost saving benefit is realized through reduced down time on the drill rig that would otherwise be required for tripping the drill string for bit changes.

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