Machine Design Module Exam 1

When using a drill press, it is important to securely hold the workpiece in place to ensure safety and accuracy. Holding the workpiece with a vise and a clamp provides stability and prevents it from moving or spinning during drilling. This allows for precise drilling and reduces the risk of accidents or injuries. Using pliers or a glove hand may not provide enough grip or stability, making it unsafe to use.

A grinder is a machine used in shaping metal by means of an abrasive wheel or removal of metals with abrasive. It is commonly used for tasks such as sharpening tools, removing excess material, or shaping metal surfaces. Grinders typically have a rotating wheel or disc that is coated with abrasive particles, which helps in grinding, cutting, or polishing the metal. This process allows for precise shaping and finishing of metal workpieces.

Knurling is the process of creating checkered depressions on the surface of a piece by rolling a tool with a pattern of straight or diagonal lines. This technique is commonly used to improve grip or to create decorative patterns on surfaces. In this context, knurling is the most appropriate choice as it aligns with the description of the process mentioned in the question.

Shaping is the correct answer because it involves a machining operation where the tool reciprocates, meaning it moves back and forth, while the feed is stationary. This process is commonly used to create flat surfaces, grooves, and contours on a workpiece. Reaming, planning, and turning do not fit the given description as they involve different types of machining operations.

Milling is the correct answer because it involves a machining operation where the tool rotates and the feed is stationary. In milling, the cutting tool spins while the workpiece remains in a fixed position, allowing the tool to remove material from the workpiece. This process is commonly used to create complex shapes and contours on various materials.

Chordal thickness refers to the width of a tooth measured along the chord at the pitch circle. It represents the distance between the top and bottom surfaces of the tooth at the pitch circle. This measurement is important in gear design and manufacturing as it affects the overall performance and durability of the gear system. By specifying the chordal thickness, engineers can ensure proper tooth engagement and minimize the risk of tooth failure or damage.

Cast iron flywheels are commonly designated with a factor of safety of 10 to 13. This means that the flywheels are designed to withstand loads that are 10 to 13 times greater than the maximum expected load. A higher factor of safety indicates a stronger and more reliable design, providing a margin of safety against potential failures or overloading. Therefore, a factor of safety of 10 to 13 for cast iron flywheels ensures their durability and ability to handle heavy loads.

A correct cutting angle on a drill for ordinary work is 59 degrees. This angle is optimal for creating clean and efficient cuts in most materials. It allows the drill bit to penetrate the material smoothly without causing excessive friction or heat buildup. A cutting angle of 59 degrees strikes a balance between sharpness and durability, ensuring that the drill bit remains effective for a longer period of time.

To prevent leakage in dynamic seals, it is recommended to use packings. Packings are materials that are inserted between two moving parts to create a seal and prevent leakage. They are commonly used in applications where there is relative motion between the sealing surfaces, such as in pumps, valves, and pistons. Packings are designed to withstand the dynamic forces and pressures involved in these applications, providing an effective seal and preventing any leakage of fluids or gases. Gaskets, seals, and felts may also be used for sealing purposes, but packings are specifically designed for dynamic seals.

For high-speed applications, it is recommended to have a maximum number of teeth in the small sprocket ranging from 18 to 24. This range allows for a balance between the number of teeth and the size of the sprocket, ensuring smooth and efficient operation at high speeds. Having too few teeth may result in excessive wear and reduced power transmission, while having too many teeth can lead to increased friction and potential jamming. Therefore, the range of 18 to 24 teeth provides an optimal solution for high-speed applications.