Plain English Meaning
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.
Full 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.
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.