Countersinking

Part of speech: noun, verb

Definitions

1. The process of creating a conical hole in a material to allow the head of a fastener to sit flush or below the surface ; the technique of enlarging the top of a drilled hole to accommodate screws or bolts with tapered heads ; a machining method used to form an angled recess enabling smooth fitting of countersunk hardware
2. Forming an angled cavity at the opening of a drilled hole so that screw heads can rest evenly or beneath the surface ; the operation of shaping a depression wider at the top to fit tapered fasteners ; producing a beveled hole end to allow proper seating of countersunk screws or bolts
3. Machining an expanding taper at the top of a hole to let screw or bolt heads sit level with or below the material surface ; the method of drilling an enlarged conical entrance to house sloped fastener heads ; shaping a bottomed recess to permit countersunk hardware to fit securely without protrusion

Etymology: A countersink is a conical hole cut into a surface so that the head of a screw or bolt can sit flush with it, and the name is a compound of two English words, "counter" and "sink." The "counter" element has travelled a long way to get there. It comes from Latin "contrā," meaning "against" or "opposite," passed through Old French "contre" and Anglo-Norman "countre," and reached Middle English as "counter" with the sense of something set against or facing something else. The "sink" element is the older, more physical part of the picture: it simply means to go downward into something. Put together, the compound describes sinking a shape into a material from the opposite side of a surface, which is exactly what a tapered hole does when it lets a fastener's head lie level with the wood or metal around it. The verb and its participle are formed the same way, so "countersinking" names the act of cutting that hole as well as the hole itself.

Synonyms: recessing, enlarging, boring