Classification of Drill Bits

The International Association of Drilling Contractors (IADC) has approved a standard classification system for identifying similar bit types available from various manufacturers [5]. Table 3-1 gives an example IADC classification chart for insert drill bits (first column). In general, the classification system adopted is a three-digit code. The first digit in the bit classification code is the rock formation series number. The letter "D" precedes the first digit if the bit is diamond or PDC drag type bit. The first digit 1 to 3 are reserved for milled tooth bits in soft, medium, and hard formation categories. The first digit 5 to 8 are for insert bits in soft, medium, hard and extremely hard formation categories.

The second digit is called the type number. Type 0 is reserved for PDC drag bits. Types 1 to 4 designate a formation hardness subclassification from the softest to the hardest formations with each series category.

The third digit is the feature number. These numbers are interpreted differently for drag bits and roller cutter bits. For diamond and PDC drag bits the features numbers are 1 to 8 and refer respectively to: step type, long taper, short taper, non-taper, downhole motor, side-track, oil base, and core ejector.

The third digit feature numbers for roller cutter bits are 1 to 7 and refer respectively to: standard roller bearings, standard roller bearing for air applications, standard roller bearing with gauge protection, sealed roller bearings, sealed roller bearing with gauge protection, sealed journal bearing, and sealed journal bearing with gauge protection.

Table 3-1: Comparison IADC chart for four manufacturers of insert tri-cone drill bits (courtesy of Reed Rock Bit Company).

Insert Bit Comparison by Type

Table 3-1: Comparison IADC chart for four manufacturers of insert tri-cone drill bits (courtesy of Reed Rock Bit Company).

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The above table also shows an insert rock bit comparison chart for four manufacturers (second through fifth columns). Feature 2 on all the bit manufacturers charts shows the insert bits designed for air drilling operations. Although the comparison chart shows insert tri-cone drill bits, the sealed roller bearing and sealed journal bearing bits are also often selected for air and gas drilling operations.

It should be noted that single cone drill bits and air hammer bits are not presently classified in accordance to the IADC code system.

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Responses

  • goytiom
    How do you compare tricone drill bits?
    8 years ago
  • feorie
    What are the classification of drill bits?
    2 years ago

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