Drilling is generally described by four characteristics: straightness, depth, straightness, and stability.

1. Hole diameter

The diameter of the borehole depends on the purpose of using it. In blasting hole drilling operations, there are many factors that affect the selection of holes. For example, the required size of rock particles after rock breaking; The type of blasting selected; The rock particles being blasted meet the requirements of "quality" (smoothness of particle surface and proportion of fragmentation); The allowable level of surface vibration during blasting operations. In larger quarries or open-pit mines, using large-diameter blasting operations often reduces the cost of drilling and blasting per ton of rock. In underground rock drilling operations, mining equipment is limited by underground space. In the drilling operation of water well holes, the size of the rock hole depends on the diameter of the pipe or the diameter requirements of the supporting equipment required by the water pump. In terms of rock support holes, the diameter of different anchor rods is the determining factor.

2. Depth of hole

The depth of the hole is influenced by the rock drilling equipment, and only short drilling tools can be selected in limited space. Short drilling tools with threaded connections are essential for drilling in confined spaces. In the drilling operation of blasting rock holes (horizontal or vertical holes), the depth of the drilled hole is slightly deeper than the theoretical depth or terrace height. In some rock drilling conditions, it is required to drill at a deeper depth (50-70 meters or deeper). Generally, the down hole drilling method is used instead of the top hammer impact drilling method. The energy transfer and powder discharge effects of the down hole drilling method are more efficient under deep hole conditions.

3. Straightness of holes

The straightness of a hole is a factor that varies greatly with the type of rock and natural conditions, the selected mining method, and the selected mining equipment. In horizontal and inclined rock drilling, the weight of the drilling tool also affects the deviation of the hole. When drilling deep blasting holes, the drilled rock holes must be kept as straight as possible to accurately achieve the desired blasting effect with explosives.

In certain types of rock drilling operations, it is often necessary to drill deeper rock holes and have extremely high requirements for the straightness of the rock holes, such as pipe holes or cable holes. Even the requirements for water well holes are very strict to ensure the smooth installation of water pipes and pumps.

Using different types of guiding equipment, such as guiding drills, guiding drill pipes, and guiding drill rods, can improve the straightness of the hole. In addition to the deviation of the rock hole itself, the direction of drilling is also related to factors such as the degree of adjustment of the advancing beam and the accuracy of the opening. So in this regard, considerable accuracy is required. Research has shown that over 50% of rock hole displacement is caused by unreasonable adjustment of the propulsion beam and poor opening.

4. Stability of pores

Another requirement for the drilled rock hole is to maintain stability until it has been charged or used for other purposes. Under certain conditions, such as when drilling loose materials or soft rock areas (where there is a tendency for detachment and blockage of rock holes), it is important to use drill pipes or rubber hoses to run along the drilled rock holes.