Countersunk Screw

A countersunk screw is a screw that is driven into material — typically soft and hardwood — so that the screw head sits below or at the surface of the wood. Countersinking is especially useful for hardwoods because the dense grain can make driving screws difficult, chewing up the wood grain and even snapping the head off the screw.

The use of a countersunk screw provides several benefits:

  • It makes it easier to drive the screw and creates a better hold
  • It preserves the integrity of the wood
  • It provides a neater finished look – no raised head or splintered edges
  • It enables a plug or cap to be used to cover the screw head and create a clean, unbroken appearance

Driving a screw into a hole that isn’t countersunk will create a very small point of contact, which applies a strong sheer force to the wood, tearing the wood grain. Hammering in a nail is the only thing worse. A countersunk screw, on the other hand, has a large contact surface in a cleanly-cut wood funnel (a tapered hole that receives the tapered screw head above the open, drilled screw shaft). The resulting direction of the force is essentially downwards, where you want it to be.

The only tool needed for a countersunk screw – in addition to a screwdriver and drill – is a countersink drill bit. A countersink drill bit can be secured in any chucked drill and will create a recess that enables a countersunk screw to sit flush with the surface of the material. The angle of the countersunk screw head determines the angle of the countersink bit needed to allow the screw head to sit flush while maintaining full contact with the base material.

To learn more about countersunk screws and select the right one for your project, contact the screw experts here at Electronic Fasteners.

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