How to Use a Diamond Coring Drill bit?
Diamond Coring Drill bit selection is important, but its correct use and reasonable operation should also be taken seriously. The two must be organically combined. The technical performance and structural characteristics of various types of drill bits should be fully utilized, and the drill bits should be layered and used alternately regularly to prevent hole deviation and improve drilling efficiency. The key points to pay attention to when using drill bits during rope drilling are as follows:
2.1 Judgment of drill bit wear and replacement
Under the premise of normal drilling without accidents, the drill bit wear should be accurately judged and the drill lifting clearance should be reasonably determined. Frequently lifting the drill to observe the drill bit wear is not conducive to improving drilling efficiency, and various accidents are often caused by improper drilling operation. Moreover, one of the essences of rope drilling is to lift the drill as little as possible to increase drilling efficiency, so this method is not feasible. In practice, the degree of drill bit wear is mainly judged according to the following three aspects.
Judging the wear of the drill bit bottom lip according to the change in drilling speed: Generally, the drill bit is properly selected, the drilling technical parameters are stable, and the decrease in drilling speed indicates core blockage or drill bit wear. The former causes a large decrease in drilling speed, while the latter causes a small decrease in drilling speed. If the drilling speed after core salvage is higher than before salvage, it means that the reduction in drilling speed is caused by core blockage; if the drilling speed before and after core salvage is similar, it means that the reduction in drilling speed is caused by Diamond Coring Drill bit wear. Judging the wear of the drill bit inner diameter based on the change in core diameter: The inner diameter of the rope coring drill bit has been firmly reinforced, and the core diameter has hardly changed under normal circumstances. However, when the inner diameter is worn, the core diameter becomes larger (close to or equal to the drill bit inner diameter), and blockage will occur frequently during drilling. The core diameter can be measured to determine whether the drill bit inner diameter is worn to ensure that the core enters the inner tube smoothly and ensures its recovery rate.
Judging the wear of the Diamond Coring Drill bit bottom lip and water inlet based on the change in pump pressure:
During drilling, the drill bit bottom lip is worn more, the water inlet becomes smaller or flattened, which will cause the pump pressure to be higher than the normal pump pressure; but core blockage or obstruction of the flushing fluid circulation channel will also cause the pump pressure to increase. To distinguish the causes, the inner tube assembly should be fished out to observe whether the core is blocked. If the core and the retaining ring are properly matched, it means that the increase in pump pressure is not caused by core blockage.
Then lift the drill tool off the bottom of the hole and pump flushing fluid into the hole. If the flushing fluid circulates normally, gently place the drill tool on the bottom of the hole. If the flushing fluid circulation channel is blocked, the drill tool should be repeatedly lifted up and down to flush the bottom of the hole. If the pump pressure is still high, it means that the bottom lip and water outlet of the drill bit are severely worn. The replacement of the Diamond Coring Drill bit should be determined comprehensively based on the above three factors such as the change range and hole depth. If the hole is deep and the drilling speed does not drop much, do not lift the drill at will. However, for severely worn drill bits, new drill bits that are suitable for the corresponding rock formations should be replaced in time and initially ground, or old drill bits (or 
old drill bits that have been processed and meet the requirements) should be queued for use.
2.2 Precautions for replacing a new drill bit
During rope core drilling, the appropriate diamond drill bit should be selected according to the drillability, abrasiveness and integrity of different rocks, and the drill bit should be repaired or replaced in time according to the wear of the drill bit. For the new diamond drill bit to be replaced, the following points should be noted:
2.2.1 Every time a new drill bit is replaced, the outer diameter of the reamer used last time must be measured accurately. It must be slightly larger than the outer diameter of the new drill bit before the new drill bit can be inserted; if the outer diameter of the reamer used last time is smaller than the outer diameter of the new drill bit, the new drill bit cannot be inserted. At this time, the new reamer must be inserted to expand the hole to the bottom or drill once before the new drill bit can be inserted.
2.2.2 Every time a new drill bit is replaced, the inner and outer diameters and heights must be accurately measured on site using a vernier caliper, and the drill bit must be initially ground.
2.2.3 If there are carbide or other metal residues at the bottom of the hole and the rock is soft, do not force the hole to be ground. It is best to drill with a needle-shaped alloy drill bit. When the rock becomes hard, lift the drill after drilling a few hundred millimeters. Only then can the hole be ground and then a diamond drill bit can be used for drilling.
