Definition
Cutting tools used to enlarge, smooth, and finish an existing hole to a precise diameter and surface quality. A reamer removes only a small amount of material and produces a hole more accurate and smoother than one made by a drill bit alone.
Plain English
A reamer is a tool that takes a hole that has already been drilled and trims it to an exact size with a clean, smooth finish. You drill the hole first, then run the reamer through it for accuracy.
Context Anchor
Seen in aircraft maintenance work when fitting bolts, bushings, rivets, or other parts that must fit tightly and correctly in a hole.
Derivation
From the Old English 'ryman,' meaning 'to widen' or 'make room.' The tool makes room in an existing hole — but only a little, and very precisely.
Why Pilots Care
Reamed holes are common in aircraft structures and engine components where close tolerances matter for strength, fit, and safety. A hole that is oversized, rough, or out-of-round can lead to loose fasteners, fatigue cracks, or component failure.
Intuition Check
A reamer is not the same as a drill bit. A drill bit makes the hole; a reamer finishes an existing hole to a more exact size.
Example Sentence 1
After drilling the hole slightly undersize, the technician used a reamer to bring it to the exact diameter specified for the bushing.
Example Sentence 2
After drilling, reamers were used to bring each hole to the exact size needed for the engine mount hardware.