Tuesday, 21 May 2013

Bit Crown Profiles for Surface-Set Diamond Core Bits


Most sizes of surface-set diamond core bits manufactured by IDP are offered in several different bit crown profiles, each of which has a specific range of application depending on the drilling conditions encountered. The most commonly used surface-set diamond bit crown profiles used for mineral exploration applications are the ‘Semi-Round’, the ‘Stepped’ and the ‘Pilot’ types. For large diameter, thick kerf surface-set diamond core bits that are used in predominantly soft, unconsolidated and abrasive formations, the Round profiles are most commonly used.

1) Semi-Round Profile

This is the most common profile for surface-set diamond mineral exploration core bits and is the standard profile for all core bits with kerf widths of 0.39 inch (10 mm) or less. Semi-round profile core bits are cost effective in that they generally have a lower overall total set carat weight than core bits with comparable kerf widths and nominal diamond sizes that use other bit crown profiles. The application range of the semi-round profile is extensive and is suitable for use in soft to hard formations and is particularly well-suited for use in fractured formations.

2)Stepped Profile

The application of this profile is primarily on medium to wide kerf, Wireline mineral exploration surface-set diamond core bits that are used to drill medium-hard formations. This profile will provide good stabilization where hole deviation is a problem and will usually yield a higher rate of penetration than any other surface-set diamond core bit crown profile. As the nose or “pilot” of this profile is relatively fragile, it is not recommended for use in heavily fractured formations. As the geometry of this profile is not well suited for the setting of large cutting elements, stepped profile surface-set diamond core bits are generally supplied with natural drill diamonds in the 10 SPC to 100 SPC size range.

3)Pilot Profile

The normal application of this profile is for narrow kerf surface-set diamond core bits that are used to drill medium-hard formations. This profile provides good stabilization where hole deviation is a problem and will usually yield a higher rate of penetration than similar kerf width core bits using the Semi-Round profile. This profile is also recommended where the width of the core bit kerf is too narrow to use the Stepped profile.

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