What Are Countersunk Screws?

William Thomson

A screw essentially is an item that allows you to fasten or secure one object to another. They are identified by a ridge, or thread, that travels the shaft and culminates at a head. This head will have either a cross- or flat-shaped impression that will enable a screwdriver to drive or turn the screw into material.

A countersunk screw is well adapted for use on thin metal and plastics.

Use a countersunk screw when you do not want the fixtures to show.

Countersunk Screw

A countersunk screw is a type of fastening that sits flush with the surface of the material it occupies. These screws typically are used so that you can cover them easily with either a screw cap or piece of wood. Other applications include the need for a fastening not to protrude so other objects can rest upon it stably, or to fasten it further to another object. The typical angle of a countersunk screw head is 82 degrees, but this varies depending on the application.

Countersunk Hole

To use a countersunk screw, it is necessary to machine the hole first for it to receive the angle of the screw head easily. Certain tools, such as a cross-hole countersink cutter and a fluted countersink cutter, can bore wood or metal efficiently to prepare a cone seating.

Other Uses

A countersunk screw also can be very useful when dealing with burred holes. Depending on how severe the hole has been burred, it can act as a readily prepared seat for the head of the screw.

Difference Between a Screw and a Bolt

There actually is no universally accepted distinction between a screw and a bolt. However, a bolt typically will be fastened with a nut that threads onto its end. One major difference is that a bolt almost never has a countersunk head.