Graphical Construction Glossary >> Tools. >> Power Tools >> Countersink Bits

Countersink Bits

Machine and hand bits for for countersinking holes in wood, metal and plastics.

Countersink, Counterbore

A depression that is made to receive the head of a screw or bolt so that it does not protrude above the surface.

Photo thanks to Wikimedia Commons, User: Glenn McKechnie

The bit above has a round shank suitable for using in an electric drill. I have a couple of smaller ones that have a hexagonal shank that suits my electric screwdriver gun. The ones shown here are said to be for "metal and timber" but in reality I would never use them for steel. The get blunt too quickly and they are hard to sharpen.

A far better method for steel is to use a larger HSS drill bit. The end bevels on them are just about the same as standard countersunk head screws. They do wear unevenly when used for countersinking work but at leasst they are easy to sharpen. If doing a lot of holes I normally make a stop for the drill bit. That is I drill through a piece of wood (something like a piece of broom handle) that is just the right length to leave the correct cutting depth showing.

Photo thanks to Wikimedia Commons, User: Cal.on

This particular one is designed for power tool use, having only one three flutes. Bits designed for use in hand tools have many more flutes or cutting edges.

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