12 1/2 inch drag BIT, thread type 4-1/2 inch

Rock drilling tools ProDrill: Step drag bit is a drill bit which has been specifically designed for drilling into soft soil and rock conditions. They are best suited for drilling into sandy soil, clay, shale, limestone, gravel, marl etc and typically used for water well drilling, mining, geothermal, and mineral exploration drilling operations being conducted into soft rock. They are also well suited for drilling pilot holes.
3 wings step type drag bit with diameter 100mm

ProDrill drag bits featuring two designs: step and chevron
Step type drill bits are designed to drill soft to medium formations while chevron type bits are for harder formations.
A step drill bit is used for drilling overburdens with sand, clay and soft formations which will produce larger cuttings than a Chevron style bit. Step drill bit is more aggressive than the Chevron, thus ROP will be higher. However, it will be less durable as well. Rotary table speed should be between 60 and 80 rpm with light weight on bit (WOB).
The step type bits are most commonly used in the field. They are primarily designed for soft to medium hard rock formation. ProDrill offers robust heavy duty drag bits suitable for drilling holes ranging from 3”to 18”, which are available in 3 wing and 4 wing design. To help ease the selection process we have classified the drag bits based on the bit diameter and American Petroleum Industry(API) Pin number.

Chevron type drill bits are used for drilling more abrasive formations like soft sandstone and shale.
The Chevron style bit is more durable than the step drill bit but because of its cutting structure, will penetrate more slowly.
Rotary table speed should be between 50 and 60 rpm with light to medium weight on bit (WOB). Harder formations require more WOB.​
ProDrill bits are commonly used for table drive rigs. Common threads are 2 3/8 IF, Mayhew regular, Failing or Mayhew Junior. The extremely long gauges help condition the hole.
Final summary:
Drage bit size:  3 7/8″ to 18″
Available threads:  2 3/8″, 2 7/8″, 3 1/2″, 4 1/2″,