WANLONG
The shape selection depends on factors such as rock type and the purpose of the diamond core drill bit. This article introduces the characteristics of several commonly used diamond core drill bit lip surfaces:
1. Rectangular lip surface:
Also known as flat bottom, it is commonly used for setting diamonds. It is easy to process and has a very small working area, so the required drilling pressure is relatively small. Under the same drilling parameters, a higher drilling speed can be achieved. However, there is a running-in process from the beginning to the bottom of the hole, that is, the penetration rate is slower at first, and only after it is ground into a small arc can the normal penetration speed be reached. Secondly, it has poor stability and is easy to cause borehole bending. This type is commonly used for drilling in medium-hard or moderately hard rocks.
2. Arc-shaped lip surface:
It can shorten the initial grinding time and is usually used in hard and medium, moderately abrasive rocks.
3. Concentric serrated lip surface:
Also known as sharp-ring groove type, the diamonds are mainly distributed on the tooth-shaped parts. The larger the particle size on the outer wall, the more it ensures the bit diameter. The tooth-shaped lip surface can produce a hole bottom with multiple free faces, allowing the bit to perform a combined grinding and shearing action on the rock, obtaining coarser powder particles, which is beneficial to diamond exposure and improves the mechanical drilling speed. Because the required axial pressure of the bit is small, it also has a better anti-deviation effect. The serrated lip surface bit is suitable for drilling in hard, dense, and weakly abrasive rock formations.
4. Stepped lip surface:
There are various types such as one-step, two-step, and three-step, which are commonly used in wireline bits and single-tube thick-wall bits. This bit has good stability during drilling, produces more free faces for rock fragmentation, and performs well, making it suitable for drilling in medium-hard rocks. At present, it is also used in hard and weakly abrasive formations, achieving good results.
5. Conical lip surface:
This bit has good bottom-hole stability and guiding performance, which helps prevent deviation. It is usually used for wireline core drilling. The conical lip surface can also be divided into inner cone, outer cone, and double cone types.
