Metal Cutting and Machining Processes

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Questions and Answers

In metal cutting, what distinguishes oblique cutting from orthogonal cutting?

  • Oblique cutting has an inclination angle between the cutting action and the job, whereas orthogonal cutting does not. (correct)
  • Orthogonal cutting is a three-dimensional cutting process, unlike oblique cutting.
  • Orthogonal cutting is the common type of cutting, unlike oblique cutting.
  • Oblique cutting involves no relative motion between the tool and the workpiece whereas orthogonal cutting does.

Which type of machining operation is primarily used for producing cylindrical jobs?

  • Planing
  • Shaping
  • Surface grinding
  • Lathe Machining (correct)

What is the main characteristic of discontinuous chips formed during metal cutting?

  • They are formed as a single, continuous piece.
  • They are produced in the form of small, individual pieces. (correct)
  • They reduce the tool life significantly.
  • They result in a poor surface finish.

What is the 'built-up edge' phenomenon in metal cutting?

<p>It is the welding of particles to the cutting tip due to heat and pressure, forming a false cutting edge. (B)</p> Signup and view all the answers

What type of material is most likely to produce continuous chips during machining?

<p>Mild steel (A)</p> Signup and view all the answers

Which of the following processes is least likely to be used for machining prismatic jobs?

<p>Cylindrical grinding (C)</p> Signup and view all the answers

What is the function of a wedge-shaped tool in traditional machining processes?

<p>To remove a layer of metal from the workpiece in the form of a chip. (A)</p> Signup and view all the answers

How do discontinuous chips typically affect the surface finish and tool life, compared to continuous chips?

<p>They lead to poorer surface finish but extend tool life. (B)</p> Signup and view all the answers

What conditions primarily contribute to the formation of a 'built-up edge' on a cutting tool?

<p>High cutting speeds and the absence of coolants. (A)</p> Signup and view all the answers

What is the primary characteristic of orthogonal cutting?

<p>No force exists perpendicular to the relative motion between tool and workpiece. (A)</p> Signup and view all the answers

Which of the following is NOT typically considered a conventional machining process?

<p>Laser cutting (A)</p> Signup and view all the answers

Which machining operation is commonly employed to create threads on a workpiece?

<p>Threading (D)</p> Signup and view all the answers

If a machining process results in small pieces of chips being produced, which of the following materials is MOST likely being machined?

<p>Cast Iron (A)</p> Signup and view all the answers

What is the purpose of 'center drilling' in machining operations?

<p>To precisely create a pilot hole for subsequent drilling operations. (B)</p> Signup and view all the answers

What is the function of the 'tail stock' in a lathe machine?

<p>To provide support to the free end of the workpiece. (A)</p> Signup and view all the answers

Flashcards

What is metal cutting/machining?

Metal cutting or traditional machining, also known as conventional machining, involves removing material to shape a workpiece.

Types of machining jobs

Machining jobs are mainly cylindrical or prismatic (flats).

Machining methods for cylindrical jobs

Cylindrical jobs are machined using lathe, milling, drilling, and cylindrical grinding.

Machining methods for prismatic jobs

Prismatic jobs are machined using shaper, planner, milling, drilling, and surface grinding.

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Orthogonal cutting

Orthogonal cutting involves forces perpendicular to the cutting motion.

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Oblique cutting

Oblique cutting involves a cutting action inclined at an angle to the job.

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Discontinuous chips

Discontinuous chips are small, separate pieces produced when machining brittle materials.

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Continuous chips

Continuous chips are long, unbroken strands produced when machining ductile materials.

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Continuous chips with built-up edge

Continuous chips with built-up edge occur when particles weld to the tool tip, forming a false cutting edge due to high heat and pressure.

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Lathe machine

A Lathe machine is a machine tool primarily used for shaping metal or other materials by removing material, typically with a cutting tool, while the workpiece is rotating.

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Facing (Lathe operation)

Facing is a machining operation on a lathe that creates a smooth, flat surface perpendicular to the axis of rotation.

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Taper turning

Taper turning is a lathe operation that produces a conical surface, gradually decreasing in diameter along its length.

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Contour Turning

Contour turning is lathe operation involves machining curved or irregular surfaces on a workpiece by using a single point cutting tool.

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Threading (Lathe Operation)

Threadingis a lathe operation where helical grooves cutting, typically onto a cylindrical or conical surface

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Drilling (Lathe Operation)

Drilling (Lathe Operation) is a cutting process that uses a drill bit to cut a hole of circular cross-section in a solid material.

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Study Notes

  • Metal cutting or traditional machining processes are also known as conventional machining processes.
  • Machining processes are carried out in machine shops or tool rooms.
  • A cylindrical or flat job is machined to a desired shape, size, and finish from a rough block using a wedge-shaped tool.
  • The cutting tool removes metal in the form of a chip.
  • Two main types of machining jobs: cylindrical and flats or prismatic.
  • Cylindrical jobs are machined using lathe, milling, drilling, and cylindrical grinding.
  • Prismatic jobs are machined using shaper, planner, milling, drilling, and surface grinding.

Metal Cutting Operation Classification

  • The position of a cutting tool's cutting edge determines if a cutting operation is orthogonal or oblique.
  • In orthogonal cutting, no force exists in the direction perpendicular to relative motion between tool and work piece.
  • Oblique cutting, a common 3D cutting type, involves the cutting action being inclined with the job at an inclination angle.

Types of Chips

  • Discontinuous chips.
  • Continuous chips.
  • Continuous chips with a built-up edge.

Discontinuous Chips

  • Discontinuous chips come out during machining.
  • The chip is produced in small pieces.
  • These chips are obtained while machining brittle material such as cast iron, brass, and bronze.
  • Fairly good surface finish is obtained and tool life is increased with this type of chips.

Continuous Chips

  • Continuous chips come out during machining.
  • These chips are obtained with ductile materials like mild steel and copper.
  • A continuous chip comes from the cutting edge of a cutting tool as a single piece.

Continuous Chip with Built-Up Edge

  • The temperature rises during cutting, and as the hot chip passes over the face of the tool, alloying and welding may occur due to high pressure.
  • This results in the formation of weak bonds in the microstructure, and weakened particles might pull out.
  • High heat and pressure cause these particles to weld to the cutting tip of the tool, forming a false cutting edge known as a built-up edge.

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