Bit Crown Profiles for Impregnated Diamond Core Bits
Most sizes of impregnated diamond core bits manufactured by Dimatec are offered in several different bit crown profiles, each of which has a specific range of application depending on the drilling conditions encountered. Some of the following bit crown profiles may not be available in certain bit sizes due to the kerf width limitations of that particular bit crown.
“Kerf width” is defined as the dimension measured across the width of the bit crown profile, that is: 0.5 x (Crown Outside Diameter - Crown Inside Diameter).
V-Ring Profile(Style ‘V’)
Unless otherwise specified, this profile is the standard for all wireline core bits as well as core bits with kerf widths greater than 7 mm (0.27 inch) that are used on conventional core barrel systems. This bit crown profile provides good penetration rates with relatively low bit loads. It is recommended for use in hard, consolidated formations and will usually provide better initial penetration rates than a bit manufactured with the “Flat-Face” (Style ‘F’) profile.
Flat-Face Profile (Style ‘F’)
This profile is the standard for all impregnated diamond core bits with kerf widths of 7 mm (0.27 inch) or less. It is also recommended for impregnated diamond core bits with kerf widths in the 7 to 20 mm (0.27 to 0.79 inch) range that are intended for use in predominantly fractured formations. This profile is less susceptible to in-hole damage than bits that are manufactured with the “V-Ring” (Style ‘V’) or the “Tapered” (Style ‘TP’) profiles. When applied in hard, consolidated formations, the “Flat-Face” profile tends to require less initial in-hole conditioning than a “V-Ring” (Style ‘V’) profile bit but usually requires the use of higher rotational speeds during the initial break-in period in order to establish a good rate of penetration.
Tapered Profile (Style ‘TP’)
This profile is limited to impregnated diamond core bits with kerf widths of 8.5 mm (0.34 inch) or greater. As the “Tapered Profile” bit crown has a significantly higher contact area with the rock face than either the “Flat-Face” (Style ‘F’), the “V-Ring” (Style ‘V’) or the “Semi-Round” (Style ‘U’) profiles, somewhat lower penetration rates may be expected. However, the “Stepped Profile” bit crown is recommended for addressing hole deviation problems encountered in wireline core drilling. This profile is also commonly used for drilling past in-hole deflecting wedges. Core bits manufactured with this profile should not be used in heavily fractured formations as the “nose” of these crowns are fairly fragile and are susceptible to in-hole damage. This profile is supplied with either the 'Extra-Wide' (Style 'XW') or the 'Face-Discharge' (Style 'FD') waterway configuration.
Semi-Round Profile (Style ‘U’)
Unless otherwise specified, this profile is the standard for all impregnated diamond core bits with kerf widths of 25 mm (0.98 inch) or greater. It is also recommended for use in highly fractured formations. The “Semi-Round” (Style ‘U’) profile is particularly well suited for use in wide-kerf core bits as it tends to distribute the bit load across the bit face more equally than either the “Flat-Face” (Style ‘F’) or the “V-Ring” (Style ‘V’) profiles. As a result, this bit crown profile will reduce the risk of “bit bouncing” during operation.