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Factors Affecting The Efficiency Of The DTH Drill
Jun 05, 2018

In addition to the correct selection of cemented carbide grades, the efficiency of DTH bits is also affected by many factors, mainly if the drill is carefully observed. Different drill bits have different shapes.

1. Bit shape

The shape of the drill directly affects the cross-section of the gun. Most drill bits are polygonal rather than round. Therefore, the polygonal section is formed when the drill bit rotates along its axis, and it is biased towards the side of the hole. In the bit process, the drill rod does not rotate in a fixed axis, but freely swings in the gun's eyes. This situation is in actual production,


When the 46 bit diameter drill bit is used, the hole is broken. When the cutting edge of the drill bit is in the I position, A is rotated, the bit rotates along the B arc and moves from I to position III. While continuing to rotate, the C point is used as the rotation point, the B arc moves along the valve, and the position of the drill bit moves from I to II, so that the reciprocating cycle is formed, and the triangle hole is formed. The actual effective diameter of the blasthole is not 46 millimeter, but 42 millimeter.

When the three bit drill bit with a diameter of 45 mm is used, the hole formation is four angle. When the drill edge is in the I position, the A point is used as the rotation point and shifted from I to skew 2. When we continue to rotate, we use the B point as the rotation point, followed by C and D as the rotation points. Such a circular rotation, forming a four angle section, the actual borehole diameter is not 45 mm, and -40 mm. Similarly, the cross hole drill bit with a diameter of 45 mm is formed with five holes.  The diameter of the gun was reduced from 45 millimeters to 40 millimeters.

From the above observation, it can be seen that the edge shape of the hole section is added to the number of the number of days of the drill bit.  When the large diameter drill bit is used, the hole is not round. The hole shape will increase the length of the fundus section and the surrounding area, and the rock around the fundus is the most difficult to break.  Therefore, to a large extent, it will affect the bit speed. The non circular hole also impedes the normal rotation of the bit. For +J- deep 4L drill, the effect is even greater, even causing the breaking of drill rod or the phenomenon of sticking. In recent years, some studies have been carried out to solve the influence of J: hole shape incircle. To find a solution to the method two, such as changing the shape of the drill bit, the thickness of the working edge of the mushroom, and raising the pressure of the Phoenix. But Shang wood shape, rock hardness, compressed air pressure, powder removal method, B diameter and hole depth. A thorough solution is needed.


Two, rock properties

Rock properties that affect drill speed are viscous, hardness and elastic.  The viscosity of rocks is the ability of rocks to resist breaking into small pieces. The nature of rocks is related to the composition and composition of rocks, the small size and shape of particles, the quantity and composition of cements, and the degree of moisture content. The viscosity of dense and homogeneous rocks is the same in all directions. The viscosity of heterogeneous or layered rocks is different in all directions.  The hardness of rock also depends on the cohesive force of rock particles. However, the hardness of rock is the ability to resist sharp tools drilling into it. The elasticity of rock is the ability to restore the original shape and volume after the external force acting on the rock has disappeared. All rocks are elastic. The elasticity of rock has obvious influence on the impact bit.


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