Figure 1: Elements of Rotary Bit (1)
Cones make up the cutting elements of the rock bit and are comprised of the following:
- Tungsten Carbide Inserts - which are pressed into the softer steel material with interface fit to hold item in place.
- Cone Thrust Button - made of a wear resistant material used to take axial bearing loads.
- Outer Cone Shell - insert land's and cone grooves.
- Cone Bore - internal ball and roller bearing races.
A >>> Nose
B >>> Inner
C >>> Next to Gage
D >>> Gage
E >>> Gage Bevel
Figure 2: Elements of Cone
Coupled in threes, by 120 degree to form the bit body and the pin connection, the lugs are machined to hold the nozzles and a journal-bearing surface.
Nozzles are used to create back-pressure in the bit to force air through the bearing airways and increase the "air-blast" force to remove and flush cuttings from the bottom of the hole. Too large of a nozzle will cause insufficient volumes of air to be delivered to the bearings, while too small of nozzle will increase the back-pressure above the compressor modulation setting. When the compressor's modulation setting is reached, it will then reduce it's volume output causing a decrease in air volume to the bit.
Figure 3: Elements of Rotary Bit (2)
Tungsten Carbide Inserts
Inserts are the actual physical elements that spall and break the rock. Inserts are made from tungsten carbide powder and a cobalt binder material, which is pressed into the designed shape then sintered. Depending on the application, the tungsten carbide inserts in a given bit will have a shape and physical properties best suited for the rock being drilled.
Figure 4: Conical Insert
The conical insert is used primarily in medium/medium-hard rock.
Figure 5: Chisel Insert
The chisel insert is used in soft/medium-soft rock. It is the standard insert in soft bits.
Figure 6: Ogive Insert
The ogive insert is used in areas where aggressiveness of the conical insert is required with additional toughness.
>>> Super Scoop
Figure 7: Super Scoop Insert
The super scoop is used in very soft rock. With the patented offset tip, digging and gouging help in sticky material.
>>> Round Top
Figure 8: Round Top Insert
The ovoid or round top insert is used in the hardest formations. Its blunt geometry gives it the most fracture resistant design. The round top is the standard insert in hard bits.
Figure 9: Trimmer Insert
The trimmer insert, used in soft to medium brittle rock formation, enhances the gage rows ability to cut the bore hole wall.
>>> Wedge Crested Chisel
Figure 10: Wedge Crested Chisel Insert
Wedge crested chisel insert are used exclusively on the gage rows of very soft to hard bits. This shape gives a fracture resistant insert that is much tougher than conical or regular chisel inserts on gage.
>>> Serrated Flat Top
Figure 11: Serrated Flat Top Insert
Serrated flat top inserts are used on shirttail lips and along the lug as "armor" to protect against shirttail and lug wear.
>>> Double Angle Conical
Figure 12: Double Angle Conical Insert
Double angle conical inserts belong hardmetal retard erosion and are able to increase ROP.