Counterbore vs. Spotface

Counterborenoun

A cylindrical recess, typically machined around a hole to admit a screw so that it sits flush with a surface.

Counterborenoun

The tool with which a counterbore is machined.

Counterboreverb

(transitive) To create such a cylindrical recess.

Counterborenoun

A flat-bottomed cylindrical enlargement of the mouth of a hole, usually of slight depth, as for receiving a cylindrical screw head.

Counterborenoun

A kind of pin drill with the cutting edge or edges normal to the axis; - used for enlarging a hole, or for forming a flat-bottomed recess at its mouth.

Counterboreverb

To form a counterbore in, by boring, turning, or drilling; to enlarge, as a hole, by means of a counterbore.

Counterborenoun

a bit for enlarging the upper part of a hole

Counterbore

A counterbore (symbol: ⌴) is a cylindrical flat-bottomed hole that enlarges another coaxial hole, or the tool used to create that feature. A counterbore hole is typically used when a fastener, such as a socket head cap screw, is required to sit flush with or below the level of a workpiece's surface.

Spotfacenoun

a shallow circular or cylindrical recess, machined on (for example) a cast part to offer a flat face against which to seat a fastener; a shallow counterbore

Spotfaceverb

(transitive) to create or fashion a spotface

Spotface

A spotface or spot face is a machined feature in which a certain region of the workpiece (a spot) is faced, providing a smooth, flat, accurately located surface. This is especially relevant on workpieces cast or forged, where the spotface's smooth, flat, accurately located surface stands in distinction to the surrounding surface whose roughness, flatness, and location are subject to wider tolerances and thus not assured with a machining level of precision.