Consider the following statements regarding sawing: 1. Vertical band saws are used for straight as well as contour cutting of flat sheets and other parts, supported on a horizontal table. 2. Friction sawing is a process in which a mild-steel blade rubs against the workpiece at speeds of up to 7,600 m/min. 3. Friction sawing process is suitable for non-ferrous metals. Which of the above statements are correct?
Sawing Statements Analysis
This solution analyzes the correctness of three statements related to sawing processes, specifically vertical band saws and friction sawing.
Statement 1 Analysis: Vertical Band Saws
Statement: Vertical band saws are used for straight as well as contour cutting of flat sheets and other parts, supported on a horizontal table.
Explanation: This statement accurately describes the function of a typical vertical band saw. The machine features a continuous band blade moving vertically, guided through the workpiece placed on a horizontal table. This setup allows for precise control for both straight cuts and intricate contour (curved) cuts on various flat materials.
Verdict: Correct.
Statement 2 Analysis: Friction Sawing Speed
Statement: Friction sawing is a process in which a mild-steel blade rubs against the workpiece at speeds of up to 7,600 m/min.
Explanation: Friction sawing relies on extremely high blade speeds to generate significant heat. This heat softens or melts the material locally, allowing the blade (often a simple steel disc without teeth) to cut effectively. Speeds ranging from 3,000 m/min up to 7,600 m/min or even higher are characteristic of this high-speed cutting method, commonly using mild steel blades.
Verdict: Correct.
Statement 3 Analysis: Friction Sawing Suitability
Statement: Friction sawing process is suitable for non-ferrous metals.
Explanation: Friction sawing is most effective on materials with relatively high melting points and hardness, such as steels and certain alloys. Non-ferrous metals (e.g., aluminum, copper) generally have lower melting points and different thermal properties. Applying the high heat from friction sawing can cause these metals to melt excessively, deform, or clog the blade, making the process generally unsuitable or requiring significant modification compared to its use on ferrous metals.
Verdict: Incorrect.
Conclusion
Based on the analysis, statements 1 and 2 are correct, while statement 3 is incorrect.
Therefore, the correct option is the one that includes only statements 1 and 2.
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______ is the process used for applying a protective finish to metallic objects.
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