A mining drill bit works by breaking and removing rock through a combination of rotation and applied force, utilizing either ploughing/scraping in softer rock or crushing/chipping in harder rock.
Here's a breakdown of the process:
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Rotation: The drill stem, to which the bit is attached, is continuously rotated. This rotation provides the cutting or grinding action necessary to break the rock.
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Thrust (Pulldown): A pulldown mechanism applies significant downward force (thrust) onto the drill bit. This force, often utilizing a large percentage (up to 65%) of the machine's weight, ensures that the bit remains in contact with the rock face with sufficient pressure to effectively break it.
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Rock Breaking Mechanism: The way the bit interacts with the rock depends on the rock's hardness:
- Soft Rock: In softer materials, the bit typically employs a ploughing-scraping action. This involves the bit essentially digging into the rock and removing material in chips or fragments.
- Hard Rock: In harder materials, the bit utilizes a crushing-chipping action. This involves applying concentrated force to fracture and chip away at the rock.
- Combination: In many cases, the bit's action is a combination of both ploughing/scraping and crushing/chipping, adapting to variations in rock hardness.
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Bit Design & Materials: The design and materials of the drill bit are critical for its performance. Bits are constructed from extremely hard and durable materials like tungsten carbide or diamond composites to withstand the abrasive forces involved in rock drilling. The specific geometry of the bit's cutting surfaces is also carefully engineered for optimal rock breaking efficiency.
In summary, a mining drill bit works by using rotational force and applied pressure to break and remove rock, with the specific method of rock removal adapting to the hardness of the material being drilled.
