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Roller cone bit is a drill bit with a medium to a large diameter that can adapt to a wide range of formations from soft to hard and is suitable for drilling industries such as oil and mining. There are various types of roller cone bits, and tri-cone bits are the most used and common ones.
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Roller Cone bits are the most widely used medium and large diameter drilling bit. When the roller cone bit is working, the cutting teeth alternately contact the bottom of the well, while rock breaking torque is small, the contact area between the cutting teeth and the bottom of the well is small and the specific pressure is high, thus it is easy to penetrate into stratum. The total length of the working blade is large, so the wear is relatively reduced. Roller cone bits can adapt to various formations from soft to hard, and are mainly used in various drilling industries such as petroleum and mining.
Features
Working Principle
When the roller cone bit is working, by providing it with sufficient axial pressure and rotary torque by drill, the roller cone bit drills and rotates on the rock at the same time and generates static pressure and impact dynamic pressure on the rock to realize rolling at the bottom of the hole. The continuous extrusion and cutting impact break the rock.
What are the shapes of the teeth of insert cone bits?
The shape of the teeth is designed according to the formation conditions. Generally speaking, sharp and long teeth are suitable for soft formations, and short and blunt teeth are suitable for hard formations.
Wedge-shaped tooth: The teeth are wedge-shaped, with tip angles ranging from 65° to 90°. It is suitable for crushing soft and medium-hard strata with high plasticity. Small tip angles are suitable for soft formations, and those with large tip angles are suitable for hard formations.
Spoon-shaped tooth: Introduced by Hughes in the 1980s, this tooth shape is an asymmetric wedge-shaped tooth. The working surface of its cutting strata is a concave spoon shape, and the back side is a slightly convex outward arc shape. This structure improves the force condition of the teeth, increases the crushing efficiency and strengthens the teeth, and can break very soft to medium soft strata rocks efficiently.
Conical tooth: The conical shape has various shapes such as a long cone, short cone, single cone, and double cone, and its strength is higher than that of a wedge-shaped tooth. Medium conical teeth with a cone angle of 60-70° are used to drill medium-hard formations, such as limestone, dolomite, and sandstone. 90° conical and 120° double conical teeth are used to drill hard rocks with high abrasiveness, such as hard sandstone, quartzite, and flint.
Spherical tooth: The top is hemispherical, suitable for highly abrasive hard formations, such as chert, quartzite, basalt, and granite, with high strength and wear resistance.
According to the number of roller cones
It includes single-cone bits, tri-cone bits, and assembled multi-cone bits. The tri-cone bits are the most popular bits used at home and abroad.
According to the cutting material
It includes milled tooth bits and insert roller cone bits.
The teeth of milled tooth bits are made of the blank roller cone by milling, mainly wedge-shaped teeth, which are divided into gage teeth, inner row teeth, and trimming teeth according to the position of teeth.
Insert roller cone bits are made of carbide material set into the hole after the hole is drilled into the roller cone.
According to the type of bearing
It includes two categories of rolling bearings and sliding bearings.
Rolling bearings have a low friction coefficient and are suitable for higher speeds, mainly used for large-diameter water well drill bits of 14 3/4 inches and above.
Sliding bearings have a stable structure, superior bearing capacity, and strong adaptability and are commonly used in various sizes of water well drill bits.
According to bearing seal type
It includes open roller, rubber sealed roller, and metal sealed bearing roller cone bits.
The inside of open roller bearings connects to the external environment. The internal processing of bearing has a channel for circulating medium circulation for cooling the bearing, which is often used with rolling bearings for drilling water wells with well depth or geothermal wells and other high-temperature geological conditions.
The structure of roller cone bit
The most commonly used mining roller cone bit is composed of three shirttails and intermeshing cone mounted on shaft journal. The cone is equipped with rollers, balls and bushings.
| Bit Dia. | IADC | Suitable Conditions | Pin Connection | Weight (kg) | Operating Suggestions WOB/RPM |
| 6 1/4”159mm | 412 | Very soft formations with low compressive strength and high drill ability | 3 1/2”API | 20 | 6250-12500lbs/60-100RPM |
| 6 1/4”159mm | 732 | Hard and abrasive formations with high compressive strength | 3 1/2”API | 20 | 25000-43750lbs/60-90RPM |
| 7 7/8”200mm | 412 | Very soft formations with low compressive strength and high drill ability | 4 1/2”API | 34 | 7880-15750lbs/60-100RPM |
| 7 7/8”200mm | 415 | Very soft formations with low compressive strength and high drill ability | 4 1/2”API | 34 | 7880-15750lbs/60-100RPM |
| 7 7/8”200mm | 535 | Soft formations with low compressive strength | 4 1/2”API | 34 | 15750-39380lbs/60-100RPM |
| 7 7/8”200mm | 542 | Medium-soft formations with low compressive strength | 4 1/2”API | 34 | 15750-39380lbs/60-100RPM |
| 7 7/8”200mm | 545 | Medium-soft formations with low compressive strength | 4 1/2”API | 34 | 15750-39380lbs/60-100RPM |
| 7 7/8”200mm | 635 | Medium-hard and abrasive formations with high compressive strength | 4 1/2”API | 34 | 23630-47250lbs/60-100RPM |
| 7 7/8”200mm | 735 | Hard and abrasive formations with high compressive strength | 4 1/2”API | 34 | 31500-55130lbs/60-90RPM |
| 7 7/8”200mm | 845 | Extremely hard and abrasive formations with high compressive strength | 4 1/2”API | 34 | 39380-63000lbs/60-90RPM |
| 9”229mm | 412 | Very soft formations with low compressive strength and high drill ability | 4 1/2”API | 50 | 9000-18000lbs/60-100RPM |
| 9”229mm | 415 | Very soft formations with low compressive strength and high drill ability | 4 1/2”API | 50 | 9000-18000lbs/60-100RPM |
| 9”229mm | 435 | Very soft formations with low compressive strength and high drill ability | 4 1/2”API | 50 | 9000-36000lbs/60-100RPM |
| 9”229mm | 545 | Medium-soft formations with low compressive strength | 4 1/2”API | 50 | 18000-45000lbs/60-100RPM |
| 9”229mm | 635 | Medium-hard and abrasive formations with high compressive strength | 4 1/2”API | 50 | 27000-54000lbs/60-100RPM |
| 9 7/8″ 251mm | 415 | Very soft formations with low compressive strength and high drill ability | 6 5/8”API | 65 | 9880-19750lbs/60-100RPM |
| 9 7/8″ 251mm | 435 | Very soft formations with low compressive strength and high drill ability | 6 5/8”API | 65 | 9880-39500lbs/60-100RPM |
| 9 7/8″ 251mm | 535 | Soft formations with low compressive strength | 6 5/8”API | 65 | 19750-49380lbs/60-100RPM |
| 9 7/8″ 251mm | 615 | Medium-hard formations with high compressive strength | 6 5/8”API | 65 | 29630-49380lbs/60-100RPM |
| 9 7/8″ 251mm | 635 | Medium-hard and abrasive formations with high compressive strength | 6 5/8”API | 65 | 29630-59250lbs/60-100RPM |
| 9 7/8″ 251mm | 645 | Medium-hard and abrasive formations with high compressive strength | 6 5/8”API | 65 | 29630-59250lbs/60-100RPM |
| 9 7/8″ 251mm | 715 | Hard and abrasive formations with high compressive strength | 6 5/8”API | 65 | 39500-59250lbs/60-90RPM |
| 9 7/8″ 251mm | 725 | Hard and abrasive formations with high compressive strength | 6 5/8”API | 65 | 39500-59250lbs/60-90RPM |
| 9 7/8″ 251mm | 735 | Hard and abrasive formations with high compressive strength | 6 5/8”API | 65 | 39500-69130lbs/60-90RPM |
| 10 5/8″ 270mm | 422 | Very soft formations with low compressive strength and high drill ability | 6 5/8”API | 74 | 10630-21250lbs/60-100RPM |
| 10 5/8″ 270mm | 415 | Very soft formations with low compressive strength and high drill ability | 6 5/8”API | 74 | 10630-21250lbs/60-100RPM |
| 10 5/8″ 270mm | 425 | Very soft formations with low compressive strength and high drill ability | 6 5/8”API | 74 | 10630-21250lbs/60-100RPM |
| 10 5/8″ 270mm | 535 | Soft formations with low compressive strength | 6 5/8”API | 74 | 21250-53130lbs/60-100RPM |
| 10 5/8″ 270mm | 615 | Medium-hard formations with high compressive strength | 6 5/8”API | 74 | 31880-53130lbs/60-100RPM |
| 10 5/8″ 270mm | 645 | Medium-hard and abrasive formations with high compressive strength | 6 5/8”API | 74 | 31880-53130lbs/60-100RPM |
| 10 5/8″ 270mm | 715 | Medium-hard and abrasive formations with high compressive strength | 6 5/8”API | 74 | 42500-63750lbs/60-100RPM |
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