Lesson Notes By Weeks and Term v3 - Senior Secondary 2
maintenance of machines
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maintenance of machines
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Subject: Wood-Work
Class: Senior Secondary 2
Term: 1st Term
Week: 5
Theme: Tools And Machine
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Identify machine parts that require: • greasing • oiling Correctly grease and oil machine parts. Give reasons for oiling and greasing machine parts.
2. 1. Introduction to Machine Maintenance Machine maintenance refers to the systematic process of inspecting, servicing, and repairing machines to ensure their optimal performance, extend their lifespan, and prevent unexpected breakdowns. Regular maintenance is crucial in woodworking to combat the harsh environment created by sawdust, wood chips, and the constant stress on moving parts. 2.
2. Lubrication Lubrication is the process of applying a lubricating substance (lubricant) between two moving surfaces in contact to reduce friction, wear, and tear. In woodworking machines, various parts move against each other, generating friction and heat, which can lead to rapid wear and damage if not managed. 2.2.
1. Reasons for Lubricating Machine Parts: The primary reasons for lubricating machine parts are: Reduce Friction: Lubricants create a thin film between moving surfaces, preventing direct metal-on-metal contact. This significantly reduces the force required for movement and minimizes heat generation.
Reduce Wear and Tear: By preventing direct contact, lubricants protect machine parts from abrasion and erosion, thus extending their operational life.
Dissipate Heat: As parts move, friction generates heat. Lubricants absorb and transfer this heat away from the critical contact points, helping to cool the machine.
Prevent Corrosion/Rust: Many lubricants contain additives that form a protective barrier against moisture and air, preventing oxidation (rusting) of metal surfaces, especially critical in Nigeria's often humid climate.
Cleanliness: Lubricants can help to flush away small particles of dirt, dust (sawdust in this case), and metal debris from bearing surfaces.
Dampen Noise and Vibration: A consistent film of lubricant can help to absorb shocks and vibrations, leading to smoother and quieter machine operation.
Enhance Efficiency: Reduced friction means less power is wasted as heat, leading to more efficient use of energy and better machine performance. 2.2.
2. Types of Lubricants: The two main types of lubricants relevant to this topic are: Oils (Lubricating Oils): These are liquid lubricants, typically petroleum-based or synthetic. They are suitable for parts requiring continuous film lubrication, easy flow, and heat dissipation.
Examples: Machine oil, motor oil (can be used for some applications in small workshops), specific cutting oils (less common for general maintenance but relevant for certain operations).
Application: Applied with an oil can, drip feed, or by an internal oiling system.
Greases: These are semi-solid lubricants, consisting of a lubricating oil mixed with a thickening agent (e.g., soap). Greases are designed for parts that require less frequent lubrication, operate under heavy loads, or where oil might leak out. They provide a thicker, more adhesive film.
Examples: Lithium-based grease, calcium-based grease, high-temperature grease.
Application: Applied with a grease gun, by hand, or packed into bearings. 2.
3. Identifying Machine Parts Requiring Greasing and Oiling It is crucial to consult the machine's operator manual for specific lubrication points and schedules.
However, general principles apply to common woodworking machines: 2.3.
1. Parts Requiring Oiling: These are typically fast-moving, smaller parts where a thin, flowing lubricant is needed for continuous film formation and heat dissipation. Motor Bearings (sealed or those with oil ports): For older models or specific designs.
Pivot Points/Hinges: On guards, fences, or tilting mechanisms (e.g., on a circular saw, bandsaw table).
Adjusting Screws and Leadscrews: For height or angle adjustments (e.g., planer bed, saw blade height).
Chains and Sprockets: On some feed mechanisms (e.g., certain types of sanders).
Fine Mechanisms: Inside gearboxes (if accessible and designed for oil, often a specific type of gear oil).
Sliding Ways: Surfaces that slide against each other for movement, often requiring a light oil. Common Woodworking Machines and Oiling Points: Circular Saw: Blade height adjustment screws, tilt mechanism pivots.
Bandsaw: Blade tension mechanism pivots, table tilt pivots, thrust bearings (some designs).
Planer/Thicknesser: Bed rollers (sometimes require a light oil), height adjustment leadscrews, feed roller chain (if exposed).
Drilling Machine: Quill (spindle housing) slides, depth stop mechanism pivots, column rack and pinion (some designs).
Sander (Belt/Disc): Drive motor bearings (if oil ports are present), tensioning mechanisms for belts. 2.3.
2. Parts Requiring Greasing: These are typically slow-moving parts, parts under heavy load, or enclosed bearings where a thick, long-lasting lubricant is needed. * *Enclosed Bearings screws, tilt mechanism pivots.
Bandsaw: Blade tension mechanism pivots, table tilt pivots, thrust bearings (some designs).
Planer/Thicknesser: Bed rollers (sometimes require a light oil), height adjustment leadscrews, feed roller chain (if exposed).
Drilling Machine: Quill (spindle housing) slides, depth stop mechanism pivots, column rack and pinion (some designs).
Sander (Belt/Disc): Drive motor bearings (if oil ports are present), tensioning mechanisms for belts. 2.3.
2. Parts Requiring Greasing: These are typically slow-moving parts, parts under heavy load, or enclosed bearings where a thick, long-lasting lubricant is needed.
Enclosed Bearings (Grease-packed): Most modern motor bearings, spindle bearings, and roller bearings are sealed and pre-packed with grease, but some older designs or larger industrial machines may have grease nipples.
Grease Nipples (Zerk fittings): These are small fittings on machine components designed to accept grease from a grease gun.
Common on: Arbor bearings (on circular saws, spindle moulders). Feed roller bearings (on planers, thicknessers). Spindle bearings (on heavy-duty drilling machines, routers). Adjusting mechanisms for heavy components.
Heavy Duty Gears: Exposed gears or gears within a gearbox designed for grease.
Bushings: Where shafts rotate within stationary sleeves. Common Woodworking Machines and Greasing Points: Circular Saw: Arbor bearings (if grease nipples are present), sometimes the bevel gear assembly.
Bandsaw: Wheel bearings (on some models), blade guide bearings (if designed for grease).
Planer/Thicknesser: Feed roller bearings, cutterhead bearings (if grease nipples are present), bed lifting mechanism gears.
Drilling Machine: Spindle bearings (especially if heavy duty), rack and pinion for table lift (some designs).
Sander (Wide Belt/Drum): Main drum bearings, conveyor belt rollers. 2.
4. Correct Procedures for Greasing and Oiling Machine Parts: 2.4.
1. General Safety Precautions (Crucial in Nigerian Workshops): ALWAYS disconnect the machine from the power source before performing any maintenance. This prevents accidental startup, which can cause severe injury. Wear appropriate Personal Protective Equipment (PPE) such as safety glasses and gloves. Ensure the work area is well-lit and free from clutter. Use the correct type and amount of lubricant. Over-lubrication can also cause problems (e.g., attracting dust, overheating). Wipe off excess lubricant immediately to prevent contamination and slip hazards. 2.4.
2. Procedure for Oiling:
1. Preparation: Disconnect power. Clean the oil port or area to be oiled from dirt and old lubricant using a clean rag.
2. Selection: Select the appropriate lubricating oil as specified by the machine manufacturer.
3. Application: Use an oil can with a spout to apply a few drops of oil to the designated points. For sliding surfaces, apply a thin film evenly.
4. Distribution: Manually move the part (if safe to do so) to help distribute the oil evenly.
5. Cleanup: Wipe off any excess oil immediately. 2.4.
3. Procedure for Greasing:
1. Preparation: Disconnect power. Clean the grease nipple or bearing housing area thoroughly. Remove any old, hardened grease if accessible (e.g., old grease seals).
2. Selection: Choose the correct type of grease.
3. Application (using a grease gun): Connect the grease gun nozzle firmly to the grease nipple. Pump the grease gun handle slowly, applying grease until a slight resistance is felt or a small amount of fresh grease appears (if it's an open bearing). For sealed bearings, pump until the specified number of pumps or until the bearing housing is filled to capacity (refer to the manual). * Avoid over-greasing, as this can lead to overheating (due to churning) or burst seals.
4. Application (manual packing): For open bearings or components without nipples, manually pack grease into the bearing rollers/ball bearings.
5. Cleanup: Remove the grease gun and wipe off any excess grease from around the nipple and the machine part. 3.
1. Teacher Activities: Introduction (10 minutes): Begin by reviewing previous knowledge about woodworking machines and their components.
Pose questions: "What happens when a bicycle chain is not oiled?" or "Why do motor vehicles need regular servicing and oil changes?" Introduce the topic of machine maintenance and lubrication, emphasizing its importance for safety and machine longevity in local workshops.
Concept Explanation (20 minutes): Clearly define lubrication, greasing, and oiling. Explain the reasons for lubrication using visual aids (diagrams showing friction, wear, corrosion). Discuss the types of lubricants (oil vs. grease), their properties, and typical uses. Use common Nigerian examples of machines that require maintenance (e.g., generators, grinding machines, wood lathes in local workshops). Identification of Machine Parts (25 minutes): Present large diagrams, posters, or actual (disconnected and safe) woodworking machines (e.g., circular saw, drilling machine, planer). Systematically point out specific components that typically require oiling (e.g., adjustment screws, pivots) and greasing (e.g., enclosed bearings, grease nipples). Explain why each part needs a specific type of lubricant (e.g., oil for fast, light movement; grease for heavy load, slow movement, or sealed bearings). Emphasize consulting the machine manual.
Demonstration of Procedures (30 minutes): Safety First: Reiterate and demonstrate the critical step of disconnecting power. Using a simplified model, a non-functional machine, or clear diagrams/videos: Demonstrate the proper technique for oiling (using an oil can). Demonstrate the proper technique for greasing (using a grease gun on a simulated grease nipple). Highlight the importance of cleanliness and wiping off excess.
Guided Practice Setup (10 minutes): Organize students into small groups. Provide simplified diagrams of woodworking machines with numbered parts. Provide empty oil cans and a non-functional grease gun or a mock-up for practice.
Question & Answer Session (5 minutes): Address any immediate questions from students. 3.
2. Student Activities: Active Listening and Note-taking: Students listen attentively and take comprehensive notes during explanations.
Observation: Students carefully observe the teacher's demonstrations of identification and application techniques.
Identification Practice: In groups, students identify and mark parts on machine diagrams that require greasing or oiling, explaining their choices.
Simulated Application Practice: Students practice the motions of oiling with empty oil cans and greasing with a non-functional grease gun on mock-up parts or designated points on a diagram.
Group Discussion: Students discuss the rationale behind using oil or grease for specific parts and the consequences of neglecting lubrication.
Response to Questions: Students answer questions posed by the teacher, demonstrating their understanding. The teacher should provide these questions for students to work through, either individually or in small groups, after the explanation and demonstration.
Question 1: Imagine you are working in a local furniture workshop in Ibadan. The circular saw's blade height adjustment mechanism feels stiff. Which type of lubricant (oil or grease) would be most suitable for this mechanism, and why?
Solution: Type of Lubricant: Oiling.
Reasoning: The blade height adjustment mechanism often involves a screw thread or a sliding mechanism. These parts benefit from a lubricant that can flow easily into the threads and provide a thin, continuous film for smooth, friction-free movement. Oil is ideal for reducing friction on such precision sliding and rotating parts, allowing for easier and more accurate adjustments. Grease, being thicker, might impede fine adjustments and attract more sawdust.
Question 2: A newly acquired industrial planer in a timber mill near Sapele has clearly marked grease nipples on its main cutterhead bearings. Describe, step-by-step, how you would correctly lubricate these bearings using a grease gun.
Solution: Disconnect Power: The first and most critical step is to always disconnect the planer from its power source to prevent accidental startup and ensure safety.
Clean Nipple: Thoroughly clean the grease nipple and the surrounding area with a clean rag to prevent dirt and sawdust from being forced into the bearing with the fresh grease.
Attach Grease Gun: Securely attach the nozzle of the grease gun to the grease nipple, ensuring a tight fit to prevent leakage.
Apply Grease: Slowly pump the handle of the grease gun, applying grease until a slight resistance is felt or the recommended number of pumps (as per the machine's manual) is achieved. Avoid over-greasing.
Remove Gun & Clean: Detach the grease gun and wipe off any excess grease from the nipple and the bearing housing to prevent it from attracting sawdust and debris.
Question 3: You observe two parts on a woodworking machine: (A) a small, fast-moving pivot point on a safety guard, and (B) a heavy-duty, slow-moving main spindle bearing with a visible grease nipple. For each part (A and B), state the appropriate lubricant and provide one reason for your choice.
Solution: Part A (Small, fast-moving pivot point on a safety guard): Lubricant: Oil.
Reason: Oil provides a thin, flowing film that is ideal for small, fast-moving pivot points, reducing friction and allowing for smooth, quick movement without resistance. It also dissipates heat effectively. Part B (Heavy-duty, slow-moving main spindle bearing with a visible grease nipple): Lubricant: Grease.
Reason: Grease is suitable for heavy-duty, slow-moving components and sealed bearings because its thicker consistency ensures it stays in place, provides a durable lubricating film under high pressure, and offers longer-lasting protection without frequent reapplication. The presence of a grease nipple indicates it is designed for grease.
Cost Savings for Artisans: In many Nigerian communities, small-scale woodworkers (e.g., furniture makers in Ojuelegba or Ladipo markets) rely heavily on affordable, often second-hand machines. Proper lubrication directly translates to extended machine lifespan, reducing the need for expensive repairs or replacement of imported parts, thereby saving operational costs and improving profitability. This skill empowers them to be self-reliant in maintenance. Safety in Vocational Training and Workshops: Understanding machine maintenance, especially the pre-lubrication safety checks (like disconnecting power), is paramount for preventing workplace accidents. This knowledge is crucial for students entering vocational trades and for existing artisans in ensuring a safer working environment in Nigerian workshops, where safety protocols may sometimes be overlooked.
Career Opportunities and Entrepreneurship: The demand for skilled technicians who can maintain and repair industrial and workshop machinery is high in Nigeria. Students with a strong understanding of machine maintenance, including lubrication practices, can pursue careers as machine operators, maintenance technicians in factories (e.g., timber processing plants, furniture factories), or even establish their own machine maintenance and repair businesses, contributing to local economic development.