Twist Drill Nomenclature

In essence, a twist drill is a steel component that is cylindrical and has unique grooves on it. The cylinder has a pointed end and a shaped end that allow it to be fastened to the drilling machine. Usually, the grooves are referred to as flutes. Twist drills are cylindrical drills made of flutes created by twisting a flat piece of steel into a cylindrical shape.

A twist drill, commonly used for drilling holes in various materials, consists of several key parts, each with specific names and functions. Here's a breakdown of the nomenclature associated with a twist drill:

1. Shank

   • Definition: The part of the drill that is clamped in the drill chuck or machine spindle.

• Types:

   • Straight Shank: Used in portable drills and small drilling machines.

   • Taper Shank: Used in machine tools for automatic centering.

2. Body

   • Definition: The portion between the shank and the point..

   • Features Contains cutting edges and flutes.

3. Point

   • Definition: The cutting end of the drill that starts the hole.

   • Components:

         • Definition: The cutting end of the drill that starts the hole.

         • Lips/Cutting Edges: The sharp edges that perform the actual cutting.

         • Point Angle: The angle formed at the tip of the drill, typically ranging from 118° to 135° depending                                       on the material being drilled.

4. Flutes

   • Definition: Helical grooves running along the body of the drill.

   • Functions:

         • Chip Removal : The flutes allow the chips to be evacuated from the hole.

         • Coolant Flow: They also provide a pathway for coolant to reach the cutting edge.

         • Helix Angle: The angle of the spiral flutes, typically 30° for general-purpose drills.

5. Land

   • Definition: The narrow surface that extends along the side of the drill, separating the flutes.

   • Function Provides support and guides the drill in the hole.

6. Margin

   • Definition: The narrow strip on the outer edge of the land.

   • Function Helps to maintain the drill diameter and reduce friction between the drill and the hole walls.

7. Web

   • Definition: The central portion of the drill body that connects the lands.

   • Function Provides structural strength to the drill.

8. Core

   • Definition: The innermost portion of the web.

   • Function The core thickness increases as it approaches the shank, giving the drill additional strength.

9. Overall Length

   • Definition: The total length of the drill from the tip of the point to the end of the shank.

10. Flute Length

   • Definition: The length of the helical grooves or flutes.

Understanding these terms helps in selecting and using twist drills effectively for various drilling applications.