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Guide to Materials and Shapes of Twist Drills

May. 20, 2023

A twist drill is a cutting tool used to drill holes in a workpiece. The process is called drilling. Universal drill bits for drilling holes in wood, plastic, metal and other materials. They are also used to create through holes in PCBs, drill through wall studs, etc. The finish after drilling is not very good, as its sole purpose is maximum metal removal. In order to obtain a good finish, the drilled hole must be machined again using a reamer or boring tool.

A twist drill consists of a cutting point located at the tip of a cylinder with a spiral groove. Twist drill bits are available in different sizes and shapes for different applications. Twist drills use different materials. They are usually made of high speed steel.

Drill material

When using twist drill bits to cut materials, especially metals, you will find that the substrate and the drill bit will heat up quickly due to friction, therefore

Twist drill bits must be made of materials that do not soften or dull when the material gets hot.

Most modern twist drills are made of high speed steel. High speed steel is a high carbon tool steel. In contrast, twist drills used to be made from ordinary carbon tool steels which, after hardening and low-tempering, retain a high degree of hardness at room temperature, but at temperatures of 200°c - 500°c the material's hardness drops to a level similar to its original softened state and it loses its cutting ability completely.

The most common types of metal drill bits are given below.

Mild steel is cheap. But it requires frequent sharpening. They are used only for drilling wood.

Due to the hardening and tempering of the material, high-carbon steel bits are more durable than low-carbon steel. High-carbon steel bits can be used for wood and metal.

HSS twist drills are harder and more heat resistant and are used for drilling metal hardwoods and other hard materials with higher cutting speeds than carbon steel tools.

Hard tungsten carbide bits, very expensive, very hard, can drill almost all materials. More brittle than steel tools.

Guide to Materials and Shapes of Twist Drills

Manufacturing process

Ground HSS (High-Speed Steel) twist drill bits are made from steel shafts, and the grooves/flutes and tips of the twist drill bits have been ground directly into shape.

Rolled HSS twist drill bits are made by a heating process called forging. The steel is flattened and then twisted into shape. This process is much shorter than the grinding process used to grind HSS twist drills. Due to the manufacturing process, rolled twist bits are usually brittle, less accurate, and less expensive.

Tip shape

When drilling through different types of materials, the angle of the tip can have a significant impact on the cutting efficiency. A simple rule of thumb is that the harder the material, the flatter the tip angle. twist bits typically have a flatter 135° angle to accommodate cutting through harder materials such as hard metals.

Another tip characteristic that can affect cutting efficiency is whether the tip is split or standard. When you try to make the initial penetration, the bit will not go through the substrate; it will hold on to the material. This is especially important because the angle of the tip becomes flatter and is used to drill harder materials.

Guide to Materials and Shapes of Twist Drills

twist drill set


Less power is required to drill the same depth and diameter of twist drill than other types of drills. Heavy feeds and speeds can be used within safe limits, thus saving a lot of time.

Good tool life, a twist drill can be used for a long time without frequent resharpening. Chips and swarf can be automatically discharged from the hole through the twist drill's chip removal groove.

Please feel free to contact GSR if you need any help. We are a German manufacturer with modern production technology and dynamic innovative power from the tool city of Remscheid with competence based on experience since 1889.  We offer you a solid promise of quality through an optimal price-performance ratio.