What is countersinking?

Countersinking involves enlarging the rim of a pilot hole.

Countersinking is especially necessary when working with hardwoods.

Why countersink?

You should only need to countersink a hole when working with countersunk screws. Countersinking a pilot hole allows a countersunk screw to sit flush with the surface of the material, giving your work a neat finish.

Without countersinking the hole, the screw may tear the fibres of the material, creating a rough work surface.

Countersink bits

Countersinking is done using a countersink drill bit; an example is shown on the left.

Most countersink drill bits have round shanks, which means they can only be used in chucks with 3 jaws. (Most cordless drill drivers will accept them but not most cordless screwdrivers.)

If you are using a cordless screwdriver, ensure you select a countersink drill bit with a hexagonal shank; an example is shown on the left.

You can purchase bits that are able to drill a pilot hole as well as countersink it; an example is shown on the left.

These types of pilot drill are also available to buy with hexagonal shanks, for use in a cordless screwdriver.