Answer any three of the following: (i) Identify two benefits of the use of cutting fluids in machining; (ii) Describe the function of a dividing head on a milling machine; (iii) Explain the term tolerance in engineering measurement systems; (iv) Describe the main factors that influence metal surface finish when parallel turning on the lathe; (v) State one advantage and one disadvantage of using magnetic chucks on a grinding machine - Leaving Cert Engineering - Question 7 - 2012

The dividing head is primarily used for precise spacing of cuts on a workpiece. For example, it allows for accurate positioning of a workpiece for making evenly spaced holes in a circle or milling features when using a pitch circle. It works by clamping the workpiece and rotating it precisely to achieve the desired cut.

Tolerance is defined as the permissible limit or limits of variation in a physical dimension. It indicates how much a measured dimension can deviate from the nominal dimension without affecting functionality. For instance, if the nominal size of a shaft is 20.00mm, and the tolerance is ±0.15mm, the shaft is acceptable in the range of 19.85mm to 20.15mm.

The main factors influencing surface finish include:

1. Cutting speed: Higher speeds generally lead to a better surface finish due to reduced cutting forces.
2. Feed rate: Lower feed rates allow for smoother cutting, enhancing the surface finish.
3. Tool condition: Sharp tools will produce a better finish compared to dull ones.
4. Vibration: Minimizing vibration during the machining process is crucial for a smoother finish.

Advantage: Magnetic chucks provide a strong and even clamping force, which secures the workpiece tightly, allowing for greater precision in grinding operations.

Disadvantage: Magnetic chucks require the workpiece to have a ferromagnetic property; thus, non-magnetic materials cannot be secured using this method.

1. It minimizes the generation of heat, which can harm both the workpiece and cutting tool.
2. It reduces wear and noise, allowing smoother operation and prolonging the lifespan of machinery.

1. Oil
2. Grease

Loading occurs when the grinding wheel becomes clogged with particles, leading to overheating and ineffective grinding. Glazing results in a shiny appearance where abrasive particles lose their sharp edges due to wear, preventing efficient grinding. Diagrams should illustrate the difference in appearance and effects on performance.

Forming is when the tool's surface contour replicates the profile required on the workpiece, shaping it directly. Generating involves creating shapes by moving the workpiece relative to a stationary cutting tool, allowing for the machining of various forms. Diagrams can demonstrate these processes effectively, showing tool paths and workpiece interactions.