WOOD
Wood drill bits are used either on the brace, or on the drilling machine. In the first case, they have a square shank. Cylindrical-shank drill bits are used with the drilling machine.
METALS
We distinguish metals according to their relative hardness when drilling. Are considered as alloys very difficult to drill cast irons and hard steel; then middle hard steels and soft steels are more current and easier to drill. Bronzes, brass, aluminum, tin and zinc are considered as soft metals face to face of the drilling..
The angle of cutting of a bit intended for the drilling of a hard metal is relatively little sharp (69°) while it will be sharper for a soft metal (49 °) exactly as for the wood. For the drilling of very hard metals, the angle of the bit up to 118 °to 140 °.
For the drilling of soft steels and soft metals, we choose brown steel drill bits with outside rectified face, proposed under the appelation: roll-forged drill bits . For drilling of soft steels and middle hard as well as for hard synthetic materials prefer ground drill bits , the soul of which is high-speed steel HSS . If we wish a long lasting material choose bits treated in nitride of titanium.
CONCRETE
The concrete is at the same time a hard and heterogeneous material. To drill it correctly, it is necessary using a drill bit able to overcoming this hardness and a system of percussion adding the effect of hammer to the rotation effect.
The drilling is not made by the removal of the chips, but by the disintegration. The capsule of tungstene, at the end of lip of cutting are the sign of recognition of the masonry drill bits intended to drill the concrete .
SOFT MATERIALS - FIBERS
Use bits identical to those used for metals, evacuating very fast residues, even a special hard materials drill bit. To obtain correct results, it is necessary to plan a protection of surface and to work at very high speed.
