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Production Technology 1 - 03 | Theory of Metal Cutting part 03 | ME | Gate 2024 Series YT
GATE Wallah (English)
Overview
This video explains the geometry of a single-point turning tool, focusing on its surfaces and angles according to the ASA (American Standards Association) and ORS (Orthogonal Rake System) standards. It details the rake face, side flank, and end flank, and then systematically introduces the various angles like back rake, side rake, and relief angles. The video also covers the nose radius and the interconversion formulas between ASA and ORS systems, concluding with a discussion on shear angle and chip thickness ratio as indicators of plastic deformation during metal cutting.
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Chapters
- A single-point turning tool has a shank, base, width, and length.
- The primary cutting edge is the main edge that performs the cutting action.
- The rake face is the surface where the chip flows after being cut.
- The side flank and end flank are the surfaces below the side cutting edge and end cutting edge, respectively, which provide clearance.
Understanding the basic parts of a turning tool is essential for identifying its functional surfaces and how they interact during the cutting process.
The video shows a physical turning tool, pointing out the shank, base, width, length, side cutting edge, and end cutting edge.
- The ASA system defines tool angles based on three mutually perpendicular planes.
- Back rake angle (alpha_b) is the inclination of the rake surface in a plane perpendicular to the base and along the tool's length.
- End relief angle is the inclination of the end flank in a plane perpendicular to the base and along the tool's length.
- Side rake angle (alpha_s) is the inclination of the rake surface in a plane perpendicular to the base and parallel to the tool's width.
- Side relief angle is the inclination of the side flank in a plane perpendicular to the base and parallel to the tool's width.
These angles are crucial for controlling chip flow, reducing friction, and preventing the tool from rubbing against the workpiece, thereby influencing cutting efficiency and tool life.
The video uses diagrams to illustrate the planes and shows how the inclination of the rake surface and flanks in these planes define the back rake, end relief, side rake, and side relief angles.
- The nose radius is the curvature at the tip of the cutting tool, connecting the side cutting edge and the end cutting edge.
- The nose radius significantly affects surface finish and chip breaking.
- The video briefly mentions end cutting edge angle and side cutting edge angle, which define the orientation of these edges relative to the workpiece.
The nose radius is a critical geometric feature that influences the quality of the machined surface and the mechanics of chip formation.
A diagram shows the curved nose of the turning tool, highlighting its radius (RN).
- The ORS system is used for analyzing forces and power in metal cutting, overcoming the complexity of the ASA system for analysis.
- In ORS, angles are defined relative to the cutting velocity vector and the chip flow direction.
- Key angles in ORS include inclination angle (i), orthogonal rake angle (alpha), side relief angle, end relief angle, approach angle (lambda), and nose radius.
- For orthogonal cutting, the inclination angle (i) is zero, meaning the cutting velocity vector is in the plane of the rake face.
The ORS provides a simplified framework for analyzing the mechanics of cutting, particularly for calculating forces and power, which is essential for machine tool design and process optimization.
The video presents the ORS angle notation (i, alpha, lambda, etc.) and explains that for orthogonal cutting, the inclination angle is zero.
- Formulas exist to convert angles measured in the ASA system to the ORS system and vice-versa.
- These formulas involve trigonometric relationships between back rake angle, side rake angle, approach angle (lambda), inclination angle (i), and orthogonal rake angle (alpha).
- The interconversion is necessary because different standards are used in practice and for theoretical analysis.
Understanding these conversion formulas allows engineers to relate tool geometry specifications from different systems, ensuring consistency in design and analysis.
The video provides specific formulas, such as tan(alpha) = tan(alpha_s) * sin(lambda) + tan(i) * cos(lambda), for interconversion.
- The shear angle (phi) is the angle between the direction of shear and the cutting velocity vector.
- The chip thickness ratio (r) is defined as the ratio of uncut chip thickness (t_c) to chip thickness (t).
- The shear angle is influenced by the uncut chip thickness, rake angle, and cutting ratio.
- The chip thickness ratio is an index of the amount of plastic deformation the metal undergoes during cutting.
The shear angle and chip thickness ratio are critical parameters that indicate the extent of plastic deformation and energy consumed during the cutting process, impacting tool wear and surface finish.
The video presents the formula for shear angle: tan(phi) = (r * cos(alpha)) / (1 - r * sin(alpha)), where 'r' is the chip thickness ratio and 'alpha' is the rake angle.
Key takeaways
- The geometry of a single-point turning tool, including its surfaces and angles, directly influences the metal cutting process.
- The ASA system provides a practical way to define tool angles for manufacturing and measurement.
- The ORS system is essential for theoretical analysis of cutting forces and power.
- Interconversion formulas are vital for bridging the gap between ASA and ORS specifications.
- The shear angle and chip thickness ratio are key indicators of plastic deformation and cutting efficiency.
- Understanding tool geometry is fundamental to controlling chip formation, surface finish, and tool life.
Key terms
Single Point Turning ToolShankRake FaceSide FlankEnd FlankBack Rake AngleSide Rake AngleRelief AngleNose RadiusASA SystemOrthogonal Rake System (ORS)Inclination AngleOrthogonal Rake AngleApproach AngleShear AngleChip Thickness RatioChip Reduction Factor
Test your understanding
- What are the primary surfaces of a single-point turning tool, and what is the function of each?
- How does the ASA system define tool angles, and what is the significance of the back rake and side rake angles?
- Why is the Orthogonal Rake System (ORS) preferred for analyzing cutting forces and power compared to the ASA system?
- What is the relationship between the shear angle, rake angle, and chip thickness ratio, and what do they indicate about the cutting process?
- Explain the importance of interconversion formulas between the ASA and ORS systems for engineers.