a drilling bit with cutting edges of hard alloys. Developed about 1900, and first used with the rotary system of drilling, it is still useful in drilling very soft formations. Also called a drag bit.

Related Terms

• Conductor Casing

generally, the first string of casing in a well. It may be lowered into a hole drilled into the formations near the surface and cemented in place; or it may be driven into the ground by a special pile drive (in such cases, it is sometimes called drive pipe); or it may be jetted into...

• Bit

1. The cutting or boring element used in drilling oil and gas wells. This bit consists of a cutting element and a circulating element. The circulating element permits the passage of drilling fluid and utilized the hydraulic force of the fluid stream to improve drilling rates. In rotary drilling, several drill collars are joined to...

• Mill

a downhole tool with rough, sharp, extremely hard cutting surfaces for removing metal by grinding or cutting. Mills are run on drill pipe or tubing to grind up debris in the hole, remove stuck portions of drill stem or sections of casing for sidetracking, and ream out tight spots in the casing. They are also...

• Cake Consistency

the character or state of the drilling mud filter cake. From API RP 13B: notations such as “hard,” “soft,” “tough,” rubbery,” and “firm” may be used to convey some idea of cake consistency....

• Circulating Components

the equipment included in the drilling fluid circulating system of a rotary rig. Basically, the components consist of the mud pump, rotary hose, swivel, drill stem, bit, and mud return line....