GRAFF Standard drill bit 12×90 is ideal for drilling bores in hard but brittle materials such as unhardened glass, porcelain and ceramics. These drill bits are not used for drilling superhard materials such as porcelain tiles or tempered glass, GRAFF diamond drill bits for ceramic granite and tiles should be used for such materials.
Flat drill bit has two carbide cutting edges, which ensures a clean drill. It is designed for dry drilling with a drill in unshocked mode. You should control the temperature of a drill bit and the working surface to avoid overheating.
The recommended drilling speed for a 12 mm drill bit is 270 rpm.