Correct option is C
The
standard point angle of a general-purpose twist drill bit is
118°. This angle is suitable for drilling most materials, including mild steel, aluminum, and other commonly used metals. The point angle determines the shape of the drill tip and affects how the drill penetrates the material. A
118° point angle provides a good balance between cutting efficiency and tool durability for general applications.
Point Angle Definition: The angle formed by the two cutting edges at the drill tip.
118° Standard:
· Provides good centering capability and reduces drill wandering.
· Balances between cutting performance and heat dissipation.
Specialized Drill Point Angles:
135° Point Angle: Used for harder materials, as it reduces thrust force and improves penetration.
90° Point Angle: Used for soft materials like plastics and wood.
Chisel Edge: The central portion of the drill bit, where the cutting edges meet, requires sufficient point angle to reduce excessive force.
Applications: Drill bits with 118° angles are widely used in general workshop, industrial, and DIY applications.
Tool geometry:
The figure shown the three most common angles,
· Point angle
· Helix angle
· Lip relief angle
