Types of Pneumatic Rock Drills
Pneumatic rock drills can be classified by mounting and feed method:
Hand-held rock drill: Operated manually; suitable for shallow, small-diameter blast holes.
Air-leg rock drill: Equipped with an air leg for support and feed; machine weight is about 23–30 kg; typically used for holes 2–5 m deep with diameters of 34–42 mm.
Upward rock drill (stoper type): Integrated air leg and main unit in a longitudinal layout; used in mining and raise driving; suitable for upward holes at 60°–90°.
Rail-mounted rock drill: Usually over 30 kg; mounted on a drilling jumbo or guide rail column; used for holes deeper than 6–10 m and diameters above 45 mm.
By impact frequency:
Medium-frequency drill: Below 2,200 blows per minute.
High-frequency drill: Above 2,400 blows per minute.
By rotation mechanism type:
Internal-rotation rock drill
External-rotation rock drill
Working Principle of a Pneumatic Rock Drill
A pneumatic rock drill operates through four coordinated actions:
Impact
Feed (thrust)
Rotation
Flushing and cuttings removal
Drilling Tools
Tapered drill rod: Forged from drill steel, typically with a hollow hexagonal section; composed of shank head, shoulder, and tail.
Drill bit: Common types include chisel bit, cross bit, T-bit, and button bit.
Overview of the Air-Leg Rock Drill
An air-leg rock drill is powered by compressed air and can drill blast holes in soft, medium, and hard rock. Typical hole diameter is 32–42 mm, and depth can reach up to 5 m. It is widely used in mine tunnel driving and various infrastructure construction projects.
Model Code Meanings for Air-Leg Rock Drills
YT27
Y: Stands for “rock” (from the equipment category)
T: Stands for “leg” (air-leg type)
27: Machine weight in kilograms
7655
Registered trademark and product model
76: Cylinder bore diameter of the rock drill
55: Piston stroke of the rock drill
FT160A
F: Stands for “auxiliary” tool
T: Stands for “leg” (air-leg)
160: Axial thrust in kilograms
A: Product revision index
