Drilling Bits
Tricones
The tricone bit - or drillhead - is the most commonly used drilling tool. It is fixed to the lower end of the drill collars which are in turn attached to the drill pipes, these being driven by the rotary movement of the turntable. This drilling tool can drill through several types of different rock structure, which is why they are they most commonly used.
Tricone bits are assemblies of three rotating cones which cut through the rock by their rotary action. The cones are fitted with longer or shorter points depending on the resistance or hardness of the rock, and teeth for softer rock. The points are made from tungsten carbide for the hardest rock. The effectiveness of a tricone bit depends on its capacity to crush the rock and remove the pieces - the tricone bit therefore works by Percussion, Penetration and Extraction.
Here is how this part looks: three arms are machined from steel, each with a trunnion. Each of the three cones mount in the trunnion in each arm. The trunnion allows the part to turn freely. A small channel is drilled into the arms of the tool to deliver grease to lubricate the roller balls. These are confined in each of the three arms of the tricone bit.
Three types of bearing exits:
- Standard ball and roller bearings without grease
- Sealed bearing with balls and rollers, with grease
- Sealed plain bearings with grease
MatFor offers three types of tricone bits, from 2-7/8" to 26".
- New tricone bits, never before used. Oil drilling only uses new tricone bits.
- Rebuilt tricone bits, which have been previously used. These tricone bits are used for water or foundations.
- "Lost" tricone bits for foundations, nearing the end of their life, having previously been used for water or oil. These may not be used in wells any more, only foundations. They are referred to as "lost" since they are left behind with the casing in the concrete, and not retrieved.
| New Tricones bits | Rebuilt Tricones bits | Tricones bits for piling |
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Drag bits
To know which drilling equipment and which tools are to be used on a site, geological studies are carried out beforehand. In the case of soft rock, a high flow pump with fast rotation is often used. Drag bits are drilling tools specially designed for this type of ground, especially for water drilling and "lost" tool foundations. Drag bits allow cuttings to be extracted at a high rate and to remove them quickly.
Drag bits are drilling tools which are less frequently used than tricones, although it is a very basic type of drilling tool. They are made with three blades mounted on the arms of the part. These bits are made with three chevron blades for ground which is mostly marl, and terraced or stepped for harder ground (limestone).
Unlike tricones, drag bits do not have a bearing, which gives them a higher rotary speed. On the other hand, since drag bits cover a larger area, breakage risks may be more frequent. Even though their blades are made of steel reinforced with carbide bits, they are relatively fragile.
The thickness, diameter and weight of drag bits varying depending on the manufacturer.
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