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          In order to improve the service life of the drill bit of the roller rig, the storage, transportation and use of the drill bit are carried out according to the normal operation, and the following measures should be taken to improve the service life of the drill bit.
    (1) Reasonable selection of the tooth profile of the roller bit
          Correct selection of the tooth profile of the roller bit can not only extend the service life of the drill bit, but also increase the piercing speed and reduce the cost of perforation. The tooth profile of the drill bit is selected mainly on the physical and mechanical properties of the rock, namely the compressive strength, hardness and drillability of the rock. In addition, the diameter and water content of the blasthole should be considered, as well as the technical performance of the roller rig:
           1. When piercing hard rock formations, we usually use ball-toothed drill bits. Because the teeth of the ball-tooth drills are shorter, the teeth are denser and can withstand large axial pressure. It is suitable for extremely hard and resistant. Perforated in the ground rock.
          2. When perforating the softer formation of rock, we usually use the wedge-shaped drill bit to make the teeth protruding longer and the teeth are sparse. It is suitable for perforation in soft rock and plastic rock.
          If the two are not properly selected, the spherical drill bit is used for perforation in soft rock. Although the service life is longer, the speed of the drill is very low. The total cost of perforation is higher after considering the cost of perforation of the rig. Conversely, if a wedge-shaped bit is used for perforation in an extremely hard and wear-resistant ore, the alloy teeth will quickly wear or break. Therefore, the reasonable choice of the drill tooth shape can improve the service life of the drill bit.
    (2) Reasonable choice of the best perforation work system
          The perforation speed of the drill bit, the physical and mechanical properties of the rock being pierced, the axial pressure exerted on the drill bit, the rotational speed of the drill, the torque of the drill bit, the shape of the tooth and the number of teeth participating in the broken rock, and the blow gun The amount of compressed air in the hole is related to many factors. According to the rock breaking mechanism of the perforation of the roller rig, the most important parameters determining the perforation working system are the axial pressure, the rotational speed and the slag discharge air volume.
    1. The effect of axial pressure on the life of the drill.
          In order to effectively break the rock, sufficient axial pressure must be applied to the drill bit so that the stress caused by the tooth is sufficient to overcome the compressive strength of the rock, but there is a certain reasonable value in the axial pressure applied to the drill bit, that is, it cannot be too large. It can't be too small. When the axial pressure value exceeds the optimum value to a certain extent, the axial pressure is further increased, and the piercing speed is not increased. If the axial pressure is too large, the hard alloy teeth may be broken or the bearing of the drill bit may be damaged.
    2. The effect of the speed of rotation on the drill bit
          Within a certain range, the perforation speed of the roller rig increases with the increase of the rotation speed of the drill, but the rotation speed is too large, which not only makes the slag discharge at the bottom of the hole difficult, but also causes secondary crushing of the rock, and it will generate strong vibration and affect the life of the drill bit. The rotation speed of the drill bit must ensure that the teeth of the cone have sufficient contact time with the rock to achieve effective volume crushing of the rock. In the hard rock, as the rotational speed increases, the impact load increases, and the wear of the teeth and bearings of the cone is significantly increased. Therefore, the use of high rotational speed is limited. However, when the rock is soft, it usually uses a high speed and a low axial pressure.
    3. Influence of exhaust air volume on bit life
          The size of the exhaust air volume directly affects the service life of the roller bit. Increasing the air volume can effectively blow the hole bottom rock and improve the condition of the broken tooth. At the same time, it reduces the wear of the claw back and can better cool the cone bearing and prolong the life of the cone. In addition, the bottom of the hole can be reduced and the effective hole depth can be increased. However, it should be pointed out that whether the bottom of the hole and the rock can be discharged smoothly depends mainly on the return air velocity, and the return air velocity is affected by the air volume and the annular space between the drill pipe and the hole wall. Therefore, when considering the effect of drainage, it is not possible to simply pursue the air compressor capability. In order to achieve the best drainage effect, and to minimize unnecessary air consumption.
    4. Improve the operating skill level of the rig driver
          During drilling, due to changes in lithology, the rotational speed and axial pressure should also change, so that the rotational speed matches the axial pressure and does not cause the bit to be eccentric. In addition, observe the following precautions:
          1 When drilling, keep the hole position clean and free of metal objects;
          2 When opening the hole, the drilling machine should be kept stable, the opening speed is not too fast, and the inclined hole is avoided, which affects the service life of the drill bit;
          3 When starting drilling or using a new drill bit, the lower axial pressure should be applied to run for a while, then increase to the normal axial pressure;
          4 Before the drill bit enters the blasthole, first open the damper to supply the drill pipe and the drill bit to pressurize the wind. During the entire piercing process, until the drill bit is raised, the supply of sufficient air volume should always be ensured;
          5 When there is a water hole or mixed with feng shui, it is easy to reduce the life of the drill bit. At this time, the drill of the appropriate nozzle should be selected to improve the wind pressure at the drill bit to protect the bearing of the drill bit;
          6 After the drill hole is drilled, the drill bit should be inspected. The temperature of the three cones should be approximately the same. The cone with the highest heat and high temperature may have the bearing air cooling duct has been rock or dirt. Blockage should be checked and treated;
          7 Do not use a curved drill pipe to drill, because the curved drill pipe is easy to subject the drill bit to unbalanced load, causing local partial wear of the drill bit and damaging the drill bit;
          8 Prevent misuse to prevent the drill bit from falling into the hole. Sudden impact load damage or scrap the drill bit;
          9 When stopping the drill for some reason, apply the hand to turn the cone and use the pressure wind to blow the cone to ensure the rotation of the cone is flexible when re-use;
          10 The rig can not continue to work during the operation process, and it can be processed in time.
          The use of a stabilizer to position the stabilizer on the upper part of the drill allows the drill to maintain a good center position, prevent the bore from deflecting, and reduce vibration and required twist. The vibration is reduced during drilling and the drill runs smoothly, which reduces tooth wear and prolongs the life of the cone and the entire drill bit. With alloy column, this enhances the wear resistance, so that the wear plate does not wear too fast, which affects the stability of the drill bit and greatly improves the service life of the drill bit.
          Over the years, through the above work practices, the service life of mining roller bits has been improved, and the cost of perforation has been significantly reduced. From the original average of 800 meters, to 1800 meters by 2010. It has certain reference value and promotion effect for the open pit mining mine to reduce the cost of perforation.
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