The 90° countersink set consists of six conical countersinks in dimensions between 6.3 mm - 20.5 mm. 
 
90° countersinks are tools for making conical offsets or for precise deburring of bores. A hole in metal should always be deburred with a countersink, as the edges of the hole are very sharp. This is useful both to avoid cutting injuries and to achieve a flat surface.
If the screw is to be countersunk into the workpiece, the hole is pre-machined with a countersink. The hole is then drilled out conically to countersink the countersunk screws into the material. In this way, the screw head is flush with the surface of the workpiece.
 
Material: HSSG
Standard: DIN 335
 
90° countersink set contains: 
6.3 mm for M 3
8.3 mm for M 4
10.4 mm for M 5
12.4 mm for M 6
16.5 mm for M 8
20.5 mm for M 10