Pt -2 Quiz 2

The correct answer is (D) All of these. A shaper is a machine tool used for shaping or machining different types of surfaces. It can be used to machine horizontal surfaces, vertical surfaces, and angular surfaces. Therefore, all of these operations can be performed on a shaper.

Hard and tough materials like cast iron should be turned at a slow speed because they are more resistant to cutting and require more force to remove material. Turning at a slow speed allows for better control and reduces the risk of overheating or damaging the material. High speeds can cause excessive heat generation, leading to tool wear and poor surface finish. Certain specific speeds may be recommended for specific operations, but in general, a slow speed is preferred for hard and tough materials like cast iron.

The tool life is affected by the depth of cut, cutting speed, and feed. These factors directly impact the wear and tear on the cutting tool during the machining process. A deeper cut puts more stress on the tool, causing it to wear out faster. Similarly, a higher cutting speed increases the temperature and friction, leading to faster tool deterioration. The feed rate also affects tool life as a higher feed rate can cause more abrasion and chipping. Therefore, all of these factors play a significant role in determining the tool life.

The correct answer is (B) VTn = C. This equation represents the relation between tool life (T) and cutting speed (V) with an exponent (n) and a constant (C). It suggests that the tool life is directly proportional to the cutting speed raised to the power of n. This means that as the cutting speed increases, the tool life decreases exponentially. The constant C represents the specific values for the tool and workpiece being used.

The vector sum of cutting velocity and chip velocity is equal to shear velocity. This means that when the cutting velocity and chip velocity are combined, they result in the shear velocity.

In metal cutting, the use of low feeds and high cutting speeds is desired when the objective is to achieve a good surface finish. Low feeds help to reduce the depth of cut, resulting in a smoother surface. High cutting speeds help to minimize the formation of built-up edge and reduce the chances of work hardening, which can negatively impact the surface finish. Therefore, option (D) is the correct answer.

Simple indexing refers to the process of dividing the workpiece into equal divisions by directly using the indexing mechanism of the milling machine. This can be done by using a dividing head or an indexing fixture. The workpiece is rotated by a certain angle for each division, allowing for the creation of any number of equal divisions. This method is commonly used in milling operations to produce accurate and precise cuts on the workpiece. Therefore, the correct answer is (B) Simple indexing.

In a center lathe, the cutting tool is fed in both cross and longitudinal directions with reference to the lathe axis. This means that the tool can move both perpendicular to and parallel to the lathe axis. This allows for a wide range of cutting operations to be performed on the workpiece, including facing, turning, and threading. The ability to feed the cutting tool in both directions gives the lathe operator greater control and flexibility in shaping the workpiece.

The size of a lathe is determined by multiple factors. The length between centers refers to the maximum length of the workpiece that can be accommodated on the lathe. The swing diameter over the bed refers to the maximum diameter of a workpiece that can be rotated on the lathe over the bed. The swing diameter over the carriage refers to the maximum diameter of a workpiece that can be rotated on the lathe over the carriage. Therefore, all of these factors contribute to determining the size of a lathe.

The angle made by the face of the tool and the plane parallel to the base of the cutting tool is called the rake angle. This angle is important in determining the efficiency of the cutting process. A positive rake angle means that the face of the tool slopes away from the cutting edge, allowing for a more efficient cutting action. A negative rake angle means that the face of the tool slopes towards the cutting edge, which can lead to a stronger cutting edge but may require more power to cut. The rake angle is an important factor in achieving the desired cutting results.

A lathe with four steps on the cone pulley and with back-gears will have four direct speeds because each step on the cone pulley corresponds to a different speed setting. Additionally, it will also have four indirect speeds because the back-gears allow for further speed variations by changing the gear ratios. Therefore, the lathe will have a total of eight speed options, four direct and four indirect speeds.

In drilling aluminum, a high helix angle is used. This is because aluminum is a soft material and has a tendency to stick to the drill bit. A high helix angle helps to reduce the friction between the drill bit and the aluminum, preventing the material from sticking and allowing for smoother drilling. Additionally, a high helix angle helps to evacuate chips more efficiently, preventing clogging and improving the overall drilling process.

A gang drilling machine is used to perform multiple drilling operations simultaneously on a work piece. It consists of multiple drill heads mounted on a single base, allowing for efficient and quick drilling of multiple holes at once. This makes it suitable for operations like drilling, reaming, counter-boring, etc. Therefore, a gang drilling machine would be the appropriate choice for performing these operations on a work piece.

A single point thread cutting tool should ideally have zero rake angle because it allows for better chip formation and reduces the cutting forces. Zero rake angle means that the cutting edge is perpendicular to the direction of cutting, which helps in achieving a clean and accurate thread profile. Positive rake angle would cause the tool to dig into the material, leading to poor surface finish and increased cutting forces. Negative rake angle would make the tool more prone to chipping and breakage. Point angle, on the other hand, refers to the angle at the tip of the tool and is not directly related to the rake angle.

The most important factor to be controlled in order to achieve a specific surface finish in single point turning is the cutting speed. Cutting speed refers to the speed at which the workpiece is rotated during the turning process. It determines the rate at which the tool cuts into the workpiece material. By controlling the cutting speed, the surface finish can be controlled as well. Higher cutting speeds result in a smoother surface finish, while lower cutting speeds may result in a rougher surface finish. Therefore, the cutting speed is crucial in achieving the desired surface finish in single point turning.

The correct answer is (C) Cutting speed, feed rate, depth of cut. This means that cutting speed has the maximum influence on tool life, followed by feed rate, and then depth of cut. This is because cutting speed refers to the speed at which the tool is moving across the workpiece, and a higher cutting speed can cause more heat and wear on the tool, reducing its life. Feed rate refers to the speed at which the workpiece is being fed into the tool, and a higher feed rate can also increase the wear on the tool. Depth of cut refers to the amount of material being removed in each pass, and while it can affect tool life, it has a lesser influence compared to cutting speed and feed rate.

The increase in nose radius actually increases tool life by reducing the stress concentration at the cutting edge and improving the tool's ability to withstand heat and wear.

The machining of titanium is difficult due to low tool-chip contact area. This means that there is limited surface area where the tool and the workpiece come into contact during the machining process. This leads to higher cutting forces and temperatures, which can cause tool wear and damage. Additionally, the low tool-chip contact area can result in poor chip evacuation, leading to chip buildup and further complications in the machining process.

Setting a boring tool above center height will result in an increase in the effective rake angle and a decrease in the effective clearance angle. This is because when the tool is above center height, it will have a greater cutting force, causing the tool to dig into the workpiece more aggressively. This increased cutting force leads to a higher rake angle, which improves cutting efficiency. At the same time, the decreased clearance angle allows the tool to maintain a closer contact with the workpiece, resulting in better chip evacuation and preventing the tool from rubbing against the workpiece.

In a vertical boring machine, the workpiece rotates while the tool remains stationary. This allows for precise and accurate drilling or boring operations to be performed on the workpiece. The vertical orientation of the machine also allows for easy access and visibility of the workpiece, making it suitable for large and heavy workpieces. Horizontal boring machines, on the other hand, have a stationary workpiece and a rotating tool. Precision boring machines and jig boring machines can have either a rotating workpiece or a rotating tool, depending on the specific design and application.