Bit Crown Profiles for Surface-Set Diamond Core Bits
Most sizes of surface-set diamond core bits maunfactured by Dimatec are offered in 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’ (Style ‘W’) and the ‘Stepped’ (Style ‘S’) types. For large diameter, thick kerf surface-set diamond core bits that are used in predominantly soft, unconsolidated and abrasive formations, the ‘Radial’ (Style ‘A’) profiles is most commonly used.
Semi-Round Profile (Style ‘W’)
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.
Stepped Profile (Style ‘S’)
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. 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 50 SPC size range.
Radial Profile (Style ‘A’)
The application of this bit crown profile is primarily for use on wide kerf, large diameter surface-set diamond core bits that are used to drill medium-hard, abrasive, unconsolidated formations. These crowns are normally set with larger sizes of natural drill diamond (>10 SPC). This bit crown profile is limited to core bits with a minimum outside set diameter of 4.70 inch (119.4 mm), a minimum inside set diameter of 2.10 inch (53.3 mm) and a minimum kerf width of 1.30 inch (33.0 mm).