noun
clearance hole
Technical term in mechanical engineering and manufacturing. A hole drilled large enough for a bolt or screw to pass through without engaging the threads.
この部品にはM6ボルト用のバカ穴が開いている。
This part has a clearance hole for an M6 bolt.
バカ穴の径はボルトの外径より少し大きくする。
The diameter of the clearance hole is made slightly larger than the outer diameter of the bolt.
Compound of バカ (foolish, useless) and 穴 (hole). The name suggests a hole that does not perform the 'smart' function of holding a thread, i.e., it is a simple through hole.