Different types of drilling bits

2022-07-29 Share

Different Types of Drilling Bits


Drilling bit is one of the most important factors for good drilling performance. Therefore, selecting the right drill bits is very critical. The drill bit for oil and gas drilling includes rolling cutter bits and fixed cutter bits.

Rolling Cutter Bits


Rolling cutter bits are also called roller cone bits or tri-cone bits. The rolling cutter bits have three cones. Each cone can be rotated individually when the drill string rotates the body of the bit. The cones have roller bearings fitted at the time of assembly. The rolling cutting bits can be used to drill any formations if the proper cutter, bearing, and nozzle are selected.

There are two types of rolling cutter bits which are milled-tooth bits and tungsten carbide inserts (TCI bits). These bits are classified by how the teeth are manufactured:


Milled-tooth bits 

Milled-tooth bits have steel tooth cutters, which are fabricated as parts of the bit cone. The bits cut or gouge formations out when they are being rotated. The teeth vary in size and shape, depending on the formation. The teeth of the bits are different depending on formations as follows:

Soft formation: The teeth should be long, slender, and widely spaced. These teeth will produce freshly broken cuttings from soft formations.


Tungsten Carbide Insert (TCI) or Insert bits generally have tungsten carbide inserts (teeth) that are pressed into the bit cones. The inserts have several shapes such as long-extension shapes, round-shaped inserts, etc.

The teeth of the bits are different depending on the formation as follows:

Soft formation: Long-extension, chisel-shape inserts

Hard formation: Short-extension, rounded inserts

Fixed Cutter Bits



Fixed cutter bits consist of bit bodies and cutting elements integrated with the bit bodies. The fixed cutter bits are designed to excavate holes by shearing formations rather than chipping or gouging formations, like rolling cutter bits. These bits do not have moving parts such as cones or bearings. The components of bits are composed of bit bodies fabricated from steel or tungsten carbide matrix and fixed blades integrated with abrasion-resistant cutters. The cutters in the bits that are available on the market are Polycrystalline Diamond Cutters (PDC) and natural or synthetic diamond cutters.


Nowadays, with the improvement that has been made in fixed cutter bit technology, the PDC bits can drill almost any kind of formation from soft to hard formation.

Polycrystalline diamond compact (PDC) drill bits are made with synthetic diamond cutters in either steel or matrix body material. PDC drill bits revolutionized the drilling industry with a wide application range and high rate of penetration (ROP) potential. 

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