Countersink

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countersink

[′kau̇nt·ər‚siŋk]
(design engineering)
The tapered and relieved cutting portion in a twist drill, situated between the pilot drill and the body.

Countersink

 

(Russian, zenkovka; from German senken, “to sink, lower”), a cutting tool used for countersinking. Countersinks usually form part of a set with centering drills. The sizes of countersinks in each set depend on the diameter of the hole; in all sets, the vertex angle is 60°. Coun tersinks are made for chamfering center holes with diameters of 0.5 to 1.5 mm (ordinary countersinks), for holes with diameters of 0.5 to 6 mm (with or without protective taper), and for holes with diameters of 8 to 12 mm (with tapered stem). Countersink cutting elements are made from high-speed steel; countersinks with tapered stems are welded and the stems are made from carbon structural steel.

countersink

countersink
A boring bit having a conical-shaped cutter; used to make a depression to receive the head of a screw or bolt so that it does not protrude above the surface.
References in periodicals archive ?
Pilot holes reduce the risk of splitting boards and allow you to get tighter-fitting, better-looking joints (especially if you use a countersink bit).
They all drove easily with no stripping or breakage and sat perfectly flush without the need for a countersink bit. We also observed no splitting when driving them near the ends of the boards.
Fasten with four screws per side, predrilling all the holes with a countersink bit to avoid splitting the wood.
Tools Smoothing plane Portable circular saw Tape measure and straight edge Combination square and pencil Coping saw (or electric jigsaw) Hammer Spoke shaves: round-bottom and flat-bottom Electric drill Drill bits: 2mm, 3mm, 5mm, countersink bits Utility knife and scissors Cork sanding block or electric sander Screwdriver (cross-headed or slotted) Here's how: Preparing the boards 1.
Countersink bits for the drill are always recommended so the fiberglass doesn't fracture.
* Countersink bits widen holes so flathead screws may be flush mounted below the surface for a finished appearance.
Tools required: Sandbug electric sander; Gofer X ultra compact rechargeable screwdriver; Pincers; Pencil; Power drill with twist and countersink bits and a knife
I say "nearly" because I have had to tuck a few extra items into it, like a bit extender, a set of pilot countersink bits and some Vix bits, so I end up with a 97-piece set instead of a 90-piece set: I'd say Ryobi pretty much hit it on the head when putting this set together.