Which angle makes rake angle in a twist drill?

Which angle makes rake angle in a twist drill? Correct Answer Helix angle

Concept:

• Drilling is a process of producing round holes in a solid material or enlarging existing holes with the use of multi-point cutting tools called drills or drill bits.
• Various cutting tools are available for drilling, but the most common is the twist drill. 

Point 

• As the drill is rotated and advanced into the workpiece, the material is removed in the form of chips that move along the fluted shank of the twist drill.
• The point angle is the angle between the cutting edges (lips).

Rake Angle: 

• It is also known as the helix angle.
• The angle between a plane passing through the drill axis and the leading edge of the land is known as rake or helix angle.
• It varies from 0° to 48°.
• Higher values are suitable for softer materials and lower values are suitable for harder materials.

Additional Information

Point angle: 

• It is also known as cutting edge angle. It is the angle included between the two opposite lips of a drill, measured in a plane containing the axis of the drill and both the lips.
• The most common value of the angle is 118°.

Chisel edge angle: 

• The obtuse angle formed between the lip and the chisel edge is known as the chisel edge angle. 
• It ranges from 120° to 135°.

Lip clearance angle

• The clearance angle is to prevent the friction of the tool behind the cutting edge.
• This will help in the penetration of the cutting edges into the material.
• If the clearance angle is too much, the cutting edges will be weak, and if is too small, the drill will not cut.
• So, the optimum value of the lip clearance angle of twist drill for general purpose should be 8 to 12°.

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