Definition
A hand tool used to clean, restore, and straighten existing threads on a bolt, stud, or inside a tapped hole without removing significant metal. Unlike a tap or die, which cuts new threads, a thread chaser follows the original thread path to remove burrs, corrosion, paint, or minor damage so a fastener can seat properly.
Plain English
A tool that cleans up threads that already exist. It runs through a damaged or dirty thread and tidies it up without cutting fresh metal.
Context Anchor
Seen during aircraft maintenance when a mechanic is cleaning up fastener threads before reinstalling hardware.
Derivation
‘Chaser’ comes from the idea of the tool ‘chasing’ — following along — the existing thread path. It does not cut new threads; it traces the ones already there.
Why Pilots Care
Cross-threaded or dirty fasteners can fail to torque correctly, which matters on aircraft hardware where proper clamping force is a safety issue. A chaser restores threads without weakening them the way a tap can.
Analogy
Like running a comb through tangled hair to straighten it out, rather than cutting new hair.
Intuition Check
A thread chaser is not mainly for making new threads. It is for cleaning up or restoring threads that are already there.
Example Sentence 1
Before reinstalling the bolt, the mechanic ran a thread chaser through the hole to remove old sealant and corrosion.
Example Sentence 2
A thread chaser restored the cylinder stud threads without requiring a full replacement.