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6.1 Explain the operating principles of a punch and shear machine - NSC Mechanical Technology Welding and Metalwork - Question 6 - 2019 - Paper 1
Question 6
6.1 Explain the operating principles of a punch and shear machine . 6.2 Describe the operating principles of the plasma cutter. 6.3 Describe the process of cutting... show full transcript
Worked Solution & Example Answer:6.1 Explain the operating principles of a punch and shear machine - NSC Mechanical Technology Welding and Metalwork - Question 6 - 2019 - Paper 1
Step 1
Explain the operating principles of a punch and shear machine.
Answer
A punch and shear machine, such as a cropper, is typically activated either manually or by foot. Its primary function is to cut steel profiles and punch holes in sheet metal. The operation is driven by hydraulic or electric mechanisms that engage various shearing blades to effectively shear or punch different profiles.
Before the punching process begins, the punches and corresponding dies must be adjusted to the desired size. Notably, the operation does not require a cooling fluid since the shear action generates minimal heat.
Step 2
Describe the operating principles of the plasma cutter.
Answer
The plasma cutter operates by creating an electrical channel of ionized gas, called plasma, which flows from the plasma cutter to the workpiece. When electrical energy passes through the ionized gas, it generates a cutting arc that effectively slices through the material.
Compressed air is typically used to blow the arc toward the workpiece through a nozzle, enhancing the cutting speed. Additionally, the nozzle may incorporate elements to control the flow more precisely, and the high-frequency arc facilitates the connection between the cutter and the workpiece.
Step 3
Describe the process of cutting an internal thread on a work piece using taps.
Answer
To cut an internal thread, follow these steps:
- Drill the hole: Begin by drilling the required hole, ensuring it matches the root or inside diameter of the desired thread.
- Use the taps in order: Select three taps, typically a taper, plug, and bottoming tap, to create the thread. Utilize them sequentially for optimal results.
- Check the thread: Once the process is complete, check the thread with a gauge or bolt to ensure proper fit.
Step 4
Describe the Brinell hardness test process.
Answer
The Brinell hardness test is conducted using a specific testing machine that employs a steel ball as an indenter. The procedure includes the following steps:
- Load application: The steel ball is pressed against the test piece with a predetermined load.
- Measurement: The diameter of the indentation left on the material surface is measured using a microscope.
- Calculation: Finally, the Brinell hardness number is computed based on the applied load and the size of the indentation.
Step 5
What is the advantage of using Rockwell hardness testing over Brinell hardness testing?
Answer
The advantages of the Rockwell hardness test include:
- Direct readout: The Rockwell hardness tester allows for immediate reading of results, minimizing the need for complicated calculations.
- Rapid testing time: The Rockwell method provides quicker results compared to the Brinell test, as it does not involve time-consuming measurement of indentations.