To cut a round hole of large diameter, to make a glass disk or a ring will help this simple tool.
It consists of three parts. The dimensions of the steel rod Ø 5 mm depend on the size of the cut holes. For small radii, it is possible to use a nail without a hat. His butt drilled hole Ø 2.4 mm and tapped M3 to a depth of 10 mm. the Second part is a steel bushing with Ø 10 mm and height 5 mm machined on the machine (allowed to use the M6 nut with inner diameter about 5 mm). In the middle of the side faces of the radial drill hole and cut a thread M2,5. Finally, the third, most miniature detail — the Central focus — the make of cut screw M2,5. Sharpen the end and speel needle files flat two flats.