Definition
A solid metal hand tool with a shaft that gradually decreases in diameter from the striking end toward the tip, used to start the removal of a tight pin, bolt, or rivet from a hole. The taper allows the punch to enter holes of varying sizes and break a part loose; once the part is moving, a straight (pin) punch is used to drive it the rest of the way out.
Plain English
A hammer-driven tool shaped like a long cone. Because it gets thinner toward the tip, it fits into different size holes and is used to start knocking a stuck pin or bolt loose. Once the pin is moving, you switch to a straight punch to push it all the way through.
Context Anchor
Seen in aircraft maintenance, especially during sheet-metal work, repair, and assembly when parts must be lined up before a fastener is installed.
Derivation
From 'taper,' meaning to gradually narrow, and 'punch,' a tool struck with a hammer to drive or mark something. The name describes the shape and the action.
Why Pilots Care
Pilots who do their own preventive maintenance, or who watch a mechanic work on their aircraft, will see this tool used to free stuck pins and bolts. Using a tapered punch all the way through a hole can damage the hole or the part — it is only meant to start the job, then a straight punch finishes it.
Analogy
It works like putting a narrow end of a peg through two slightly misaligned holes, then sliding it in farther until the holes line up.
Intuition Check
Do not think of “punch” here as a tool for making a clean new hole. A tapered punch is mainly for lining up existing holes or starting a part moving.
Example Sentence 1
The mechanic used a tapered punch to start the hinge pin moving, then switched to a straight punch to drive it the rest of the way out.
Example Sentence 2
To free the binding bolt, the technician tapped lightly with a tapered punch until the fastener began to move.