A common usage of the countersunk hole is to allow the head of a flat head bolt or screw, when placed in the hole, to sit flush with or below the surface of the surrounding material. A Countersunk Hole is made with use of a drill bit and treating a laser cut hole with the bit to taper out the countersink.

How is a countersink made?

Form countersinking

There are two processes for producing formed countersinks: coin dimpling and modified radius dimpling. Such dimples in fairly thick sheet can even be tapped to yield a threaded hardpoint on the sheet without the bother and expense of welding a nut to the sheet.

Which screws are used for countersunk screws?

A countersunk screw is a screw that is “sunk” into a piece of lumber. The head will sit below the surface of the material and it can easily be filled with a wood plug or filler. Bolts and large hex-head screws can also be countersunk. Each require a special countersink bit for the best results.