What Is A Twist Drill? Different Material Used For Drill And Their Properties

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What is a twist drill?

A twist drill is a cutting tool that used to create holes in the workpiece.  The process is known as drilling. The general purpose drill bit to create a hole in wood, plastic, metal and other materials. They are also used to create through holes in the PCB, drill through wall studs, etc. The finish after the drilling is not so good because its sole purpose is the maximum metal removal rate. In order to obtain a good finish, drilled hole must be machined again by using a reamer or by the boring tool.

Twist drill comprised of a cutting point at the tip of cylindrical body with helical flutes. Twist drill bits are come in different size and shape for the different purpose.  Different materials are used for twist drill. They are usually made of high-speed steels.

Read: Twist Drill Nomenclature/ Parts of a Twist Drill

Different drill material and their properties

Most common types of metal drill bits are given below
Low carbon steel
  • Inexpensive
  • Do not hold cutting edge well; it requires frequent sharpening.
  • They are used only for drilling of wood

High carbon steel
  • High carbon steel drill bits are durable than low carbon steel due to hardening and tempering of material.
  • High carbon steel drill bits can use on wood and metal 
  • Tool lost their temper at high temperature

High-speed steel
  • High speed twist drills are harder and more resistant to heat
  • Used to drill metal hardwood and other hard material
  • High cutting speed than carbon steel tools
Read: Heat Generation Zones in Metal Cutting

Cobalt steel alloys
  • It is a variation of high-speed Steel that contains more Cobalt content
  • Hold their hardness at high temperature, but they are more brittle than high-speed steel.
  • Used to drill harder material like stainless steel

Tungsten carbide
  • Carbide drill bits are expensive
  • Extremely hard, it can drill virtually all material
  • More brittle than Steel tools

Polycrystalline Diamond
  • Hardest material used for drill tool
  • Extremely resistant to wear
  • The diamond tool cannot used to machining of ferrous material because it causes a reaction between the carbon in PCD and iron. The result is tool wear.

To know more about the tool material read Different Types of Cutting Tools Materials and Their Properties

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