Definition
A hand tool used to mark the exact location of a hole that needs to be drilled in a second piece of material so it lines up perfectly with a hole already drilled in the first piece. The tool fits snugly into the existing hole and has a sharp point on the opposite end that, when struck, leaves a small dimple on the underlying material indicating where to drill.
Plain English
A small pointed tool that uses an existing hole as a guide to mark exactly where a matching hole should be drilled in a piece of material underneath.
Context Anchor
Seen in aircraft maintenance, sheet-metal work, and parts fitting when a mechanic needs a new hole to match an existing one.
Derivation
Called a 'transfer' punch because it transfers the position of an existing hole onto a new piece of material. 'Punch' comes from the Old French 'ponchon,' meaning a pointed tool used to pierce or mark.
Why Pilots Care
Accurate hole transfer maintains structural integrity and prevents stress concentrations in airframe repairs.
Intuition Check
A transfer punch is not mainly for punching a full hole through metal. It is used to mark the center of a hole so the hole can be drilled accurately later.
Example Sentence 1
The mechanic used a transfer punch to mark the new skin so the rivet holes would line up with those in the underlying rib.
Example Sentence 2
After fitting the new bracket, he reached for the transfer punch to copy the mounting holes onto the fuselage frame.