How to pick a bit?

Here's how to pick a bit based on three basic bits: material, coating and geometric features.
01, how to choose the material of the drill
Materials can be roughly divided into three types: high speed steel, cobalt high speed steel and solid carbide.
High speed Steel (HSS) : 

High-speed steel has been used as a cutting tool for more than a century since 1910. It is the most widely used and the cheapest cutting tool material available today. High-speed steel bits can be used both on hand drills and in more stable environments such as drilling presses. Another reason for the durability of high-speed steel may be that its tools, which can be repeatedly sharpened, are cheap enough to be used not only as drill bits but also as turning tools.

Cobalt high speed Steel (HSSE) : 

Cobalt-containing high speed steel has better hardness and red hardness than high speed steel. The increase in hardness also increases wear resistance, but at the same time, some toughness is sacrificed. Like high speed steel, they can be polished to improve their use.

CARBIDE: 

Cemented carbide is a composite material of metal base. Among them, tungsten carbide is used as the matrix, and some materials of other materials are used as adhesives through a series of complex processes such as hot isostatic pressing for sintering. In hardness, red hardness, wear resistance and other aspects compared with high speed steel, there is a huge improvement, but the cost of carbide tool is also more expensive than high speed steel. Cemented carbide in tool life and processing speed than the past tool materials have more advantages, in the repeated grinding tool, the need for professional grinding tools.