Countersinks & Countersink Drills

COUNTERSINKING SCREWS AND OTHER FITTINGS FLUSH WITH THE MATERIAL SURFACE

Basically, three different tools are suitable for countersinking screws:

1. The upper end of the hole drilled for the screw can be widened with a countersink so that the screw can be screwed in so far that its head is below the surface of the wood. This requires two operations (drilling and countersinking), as well as a tool change.
2. With a countersink drill, there is no need to change tools and there is only one operation. The drill is fitted with a countersink so that the guide hole for the screw and the countersink can be drilled in one go.
3. Instead of keeping drill countersinks of the appropriate diameter for countersunk holes, the existing drills can also be fitted with appropriate slip-on countersinks. This solution offers the additional advantage that blunt drills can easily be replaced by sharp ones instead of having to resharpen them.

Basically, pre-drilling the screw hole is essential for screw fastened joints, because pre-drilling and countersinking the screw hole at the same time prevents the wood from splitting.

For hexagonal screws and similar fittings, you can also countersink with a tenon countersink. These tools are similar to the well-known Forstner drills and, like them, cut a blind hole with a flat drilled base.