Surface Set Diamond Core Bits

Surface set core bits, as the name suggests, are set with a single layer of natural diamonds on the working surfaces of the bit crown, arranged in a specific pattern.

Unlike impregnated diamond bits where controlled erosion of the matrix crown is required to expose new diamonds, the matrix bond used in surface set bits is extremely tough and wear resistant. The only function of the matrix on a surface set bit is to securely hold the diamonds in position throughout the operational life of the bit.

Surface set bits are used for drilling soft, abrasive, unconsolidated formations that are not effectively drilled by impregnated diamond bits. They can also be used for drilling harder formations with low powered drills, where the rotational speed or bit load produced is not sufficient to run impregnated bits.

Surface set bits provide higher rates of penetration than impregnated bits in soft formations due to the greater degree of exposure of the individual diamond stones. However, as they are set with only a single layer of diamonds, they generally yield a lower overall bit life.

Available with a range of diamond stone sizes and crown profiles to suit different rock formations.

Advantages:

Can be cost-effective for coring soft formations
Can be used with low powered drills

Crown Profiles

Semi-round Profile

This is the most common profile for surface-set diamond core bits and is the standard profile for all core bits with crown widths of 10mm or less. Suitable for use in soft to hard formations and is particularly well suited for use in fractured formations.

Stepped Profile

This profile is used mainly on medium to wide crown wireline core bits for coring in medium-hard formations. This profile provides good stabilization where hole deviation is a problem. As the nose of this profile is relatively fragile, it is not recommended for use in heavily fractured formations. Stepped profile surface-set core bits are usually supplied with natural diamonds in 10-50 SPC size range.