a. The hydraulic drills
b. Electric motor drills
c. Pneumatic rock drills
The above types of tools are utilized in different types of projects like soil nailing, micro-pile, mining and tunneling job sites. The hydraulic drills are mostly recognized due to their light weight and capacity to operate on hard rocks devoid of utilizing a large compressor.
Parts of a Rock Drill: All types of rock drills contain a standard design that is basically a combination of exchangeable attachments. A standard rock drill comprises of the following sections:
1. Drill bit: It refers to the tip of the rock drill that initially touches with the ground throughout a boring operation.
2. Drill stem: It stands for the long frame that enters the ground throughout boring whose end houses the drill bit.
3. Drill rod: It belongs to the empty section of the drill stem that attaches the motor of the rig to the drill bit. The drill rod transmits the cutting force to the drill bit to allow the rock drill to enter into the ground.
4. Carbide bits: These belong to special types of drill bits which are found in rotary and percussive drilling containing carbide tungsten coated onto them at an angle.
How Rock Drills Work: All through soil nailing, micropile, mining or tunneling operations, rock drills enter the earth either by rotating or making incessant impact blows.
Rotary drills are activated by cutting and flushing out rock fragments, whereas percussive drilling splits rocks by making impact blows. Some contractors prefer to join both methods which are suitable for operations on medium to hard rocks.
The method of drilling is based on the type of hole a contractor plans to bore into the ground. The two mostly recognized holes are the cored holes and the open holes. Cored holes contain an opening whose diameter is preset beforehand prior to start of an operation. In this case, cored holes need a stem with exterior tubes to rotate the drill bit.
Alternatively, open holes do not contain predetermined diameter. The drill bit enters straight into the ground throughout an operation. The three main types of drill bits generally exist which are used in boring open holes. These range from rock roller bits, wing bits and down-the-hole hammers.
Rock roller bits alias tricone bits, contain teeth-like steel cones. These cones cut and flush rock fragments outsides via the drill rod. Wing bits alias drag bits, are built with carbide tungsten and effective for soft ground surfaces. Air core hammers contain three protruding blades that cut rock throughout an operation and apply compressed air to flush out fragments on the surface.