Definition
A twist drill whose shank (the end held by the drilling machine) is ground to a gradual taper rather than being straight. The taper fits directly into a matching tapered socket in the drill press spindle, where friction alone holds the drill secure and centered during cutting. Larger drills typically use this design because a chuck cannot grip them reliably under heavy cutting loads.
Plain English
A drill bit with a cone-shaped back end that wedges directly into the drill press, instead of being clamped in a chuck. The taper grips itself when pushed in.
Context Anchor
Seen in aircraft maintenance tool descriptions and shop procedures, especially when larger or heavier drilling work is done on metal parts.
Derivation
‘Shank’ comes from Old English ‘scanca’ meaning leg or shaft — here it refers to the back portion of the drill that gets held. ‘Tapered’ simply describes its cone shape. Together: the shaft end of the drill is cone-shaped rather than straight.
Why Pilots Care
Provides vibration-free, accurately sized holes essential for structural repairs and component installation where loose tolerances could compromise safety.
Intuition Check
The taper is on the holding end of the drill bit, not on the hole-making end. A tapered-shank drill is named for how the machine holds it.
Example Sentence 1
For the larger holes in the wing spar fitting, the mechanic selected a tapered-shank drill and seated it directly in the drill press spindle.
Example Sentence 2
After sharpening, the tapered-shank drill was inserted into the drill-press socket and used to enlarge rivet holes on the fuselage skin.