Definition
A pointed cutting tool with two helical (spiral) flutes running up its body, used in a drill press, hand drill, or power drill to cut round holes in metal, wood, plastic, or composite materials. The flutes carry chips out of the hole as the drill rotates, and the angled cutting edges at the tip do the actual cutting.
Plain English
The most common type of drill bit. It is a metal rod with two spiral grooves cut into it and a sharp point on the end. When it spins, the point cuts a round hole and the grooves clear out the shavings.
Context Anchor
Seen in aircraft maintenance tasks that involve drilling holes for fasteners, repairs, or part installation.
Derivation
Called 'twist' because the flutes are twisted in a spiral (helix) along the length of the bit. That spiral shape is what lifts chips out of the hole as the bit cuts -- without it, debris would pack in and stop the cut.
Why Pilots Care
Aviation technicians use twist drills constantly -- for drilling out rivets, opening up holes for new fasteners, and repair work. Choosing the right size, sharpness, and material of twist drill matters because oversized or wallowed-out holes weaken the structure.
Intuition Check
Do not confuse a twist drill with the powered drill motor. The twist drill is the bit that does the cutting; the drill motor is the tool that turns it.
Example Sentence 1
The technician selected a 3/32-inch twist drill to remove the damaged rivet from the wing skin.
Example Sentence 2
After sharpening the twist drill, the mechanic checked the diameter against the rivet gauge before continuing the repair.