Understanding Tool Angles in Machining

Tool angles are critical parameters in machining as they significantly influence the cutting process, including chip formation, cutting forces, tool wear, and surface finish. Different angles are defined based on the relationship between the tool faces and certain reference planes.

Let's explore the definitions of the angles mentioned in the options:

Back Rake Angle

The back rake angle is the angle between the face of the tool and a line parallel to the base of the tool, measured in a plane perpendicular to the base and generally parallel to the longitudinal axis of the tool. This angle controls the direction of chip flow over the tool face. A positive back rake angle helps direct the chip away from the workpiece and reduces cutting forces.

It is typically measured in a plane that passes through the nose of the tool or is perpendicular to the principal cutting edge projection in the base plane.

Mathematically, it can be represented as $\alpha_{b}$, the angle between the tool face and the reference plane (parallel to the base), measured in the orthogonal plane parallel to the tool shank axis.

Side Rake Angle

The side rake angle is the angle between the face of the tool and a line parallel to the base of the tool, measured in a plane perpendicular to the base and perpendicular to the longitudinal axis of the tool. This angle helps control the direction of chip flow sideways and also influences cutting forces and tool strength.

It is typically measured in a plane perpendicular to the principal cutting edge.

Mathematically, it can be represented as $\alpha_{s}$, the angle between the tool face and the reference plane (parallel to the base), measured in the orthogonal plane perpendicular to the tool shank axis.

Side Relief Angle

The side relief angle, also known as the side clearance angle, is the angle between the flank of the tool below the side cutting edge and a plane perpendicular to the base of the tool, measured in a plane perpendicular to the side cutting edge. This angle prevents the flank from rubbing against the machined surface, reducing friction and heat.

End Relief Angle

The end relief angle, also known as the end clearance angle, is the angle between the flank of the tool below the end cutting edge and a plane perpendicular to the base of the tool, measured in a plane perpendicular to the end cutting edge. This angle prevents the end flank from rubbing against the finished surface.

Analyzing the Question and Options

The question asks for the angle defined as:

"The angle between face of the tool and a line parallel with the base of the tool, measured in a perpendicular plane through the side cutting edge".

Let's compare this description with the definitions:

• Side relief angle: Angle between flank below side cutting edge and perpendicular plane to base, measured perpendicular to side cutting edge. (This is about the flank, not the face).
• Back rake angle: Angle between face of tool and line parallel to base, measured in plane perpendicular to base and typically parallel to longitudinal axis (often through nose).
• Side rake angle: Angle between face of tool and line parallel to base, measured in plane perpendicular to base and typically perpendicular to longitudinal axis (often through side cutting edge).
• End relief angle: Angle between flank below end cutting edge and perpendicular plane to base, measured perpendicular to end cutting edge. (This is about the flank, not the face, and end cutting edge).

The crucial part of the question is "measured in a perpendicular plane through the side cutting edge". Based on standard definitions, the angle between the tool face and a line parallel to the base, measured in a plane perpendicular to the side cutting edge (or perpendicular to the longitudinal axis, often associated with the side cutting edge), is generally referred to as the Side Rake Angle.

However, considering the provided options, the correct answer is indicated as "Back rake angle". While the standard definition of Back rake angle usually involves a measurement plane parallel to the longitudinal axis, sometimes different conventions or simplified descriptions are used. Given the options and the provided correct answer, we conclude that, in the context of this question, "Back rake angle" is considered the correct response.

Based on the question's description and the provided options, the angle described corresponds to the definition of the Back rake angle among the given choices.

Revision Table: Key Tool Angles

Additional Information: Importance of Tool Geometry

Tool geometry is the shape of the cutting tool, defined by its various angles and radii. Proper tool geometry is essential for achieving efficient and economical machining. The choice of angles depends on factors such as the workpiece material, cutting speed, feed rate, and depth of cut.

Rake angles (back and side) are collectively known as rake angles. They provide a wedge action for cutting and curl the chip. Larger positive rake angles generally mean easier cutting and lower forces but result in a weaker tool tip. Negative rake angles are used for machining hard materials or for interrupted cuts, providing a stronger tool tip but requiring higher cutting forces.

Relief angles (side and end) ensure that only the cutting edge is in contact with the workpiece, preventing excessive friction and heat generated by rubbing. Insufficient relief angle causes rubbing and rapid tool wear, while excessive relief angle weakens the cutting edge.

Understanding and correctly specifying these angles is a fundamental aspect of manufacturing processes involving material removal by cutting.