Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Identify safety devices on workshop machines.
• Demonstrate correct operation of a bench grinder.
• Perform basic preventative maintenance on a drill press.
• Identify common causes of machine malfunction.
• Explain the importance of a planned maintenance schedule.

Lesson summary

This week, we delve into the essential aspects of basic machine operations and maintenance. Understanding these principles is crucial not just for your Mechanical Technology studies, but also for practical applications in various aspects of life, from household repairs to potential careers in South Africa's manufacturing and engineering sectors. Consider the importance of reliable machinery in our mines, factories, and even in keeping our transport systems running. Without proper operation and maintenance, these vital systems would fail, impacting the economy and daily lives significantly.

Lesson notes

This week, we focus on the bench grinder and drill press as representative machines for understanding basic operations and maintenance.

A. Bench Grinder Operation and Maintenance: Function: The bench grinder is used for sharpening tools, removing burrs from metal, and shaping materials. It consists of two abrasive wheels (grinding wheels) mounted on a motor-driven shaft.

Safety: Eye protection: Always wear safety glasses or a face shield. Flying sparks and debris can cause serious eye injuries.

Wheel guards: Ensure the wheel guards are in place and properly adjusted. These guards protect you from flying fragments if a wheel breaks.

Tool rests: The tool rests should be adjusted to within 3mm of the grinding wheel. This provides support and prevents the workpiece from being pulled into the wheel.

Spark deflectors: Adjust spark deflectors to redirect sparks away from the operator.

Wheel condition: Inspect the grinding wheels for cracks or chips before each use. Replace damaged wheels immediately.

Personal Protective Equipment (PPE): Closed-toe shoes are essential in a workshop environment. Avoid loose clothing that could get caught in moving parts.

Operation: Starting: Ensure the power switch is off. Check the grinding wheels for any damage. Put on your safety glasses or face shield. Turn on the grinder.

Grinding: Hold the workpiece firmly against the tool rest. Apply light, even pressure to the grinding wheel. Move the workpiece back and forth across the wheel to prevent overheating and uneven wear. Avoid grinding on the sides of the wheel.

Cooling: Dip the workpiece in water frequently to prevent overheating. Overheating can damage the workpiece and cause it to lose its temper (hardness).

Stopping: Turn off the grinder and allow the grinding wheels to come to a complete stop before leaving the machine.

Maintenance: Wheel Dressing: Grinding wheels can become glazed or loaded with metal particles, reducing their effectiveness. Use a wheel dresser to clean and reshape the grinding wheel.

Cleaning: Regularly clean the grinder to remove metal dust and debris. Use a vacuum cleaner or brush.

Wheel Inspection: Regularly inspect grinding wheels for cracks, chips, or other damage. Replace damaged wheels immediately.

Bearing Lubrication: Lubricate the motor bearings according to the manufacturer's instructions. This will help to prolong the life of the motor.

B. Drill Press Operation and Maintenance: Function: The drill press is used for drilling holes in metal, wood, and other materials. It consists of a motor, a spindle that holds the drill bit, and a table that supports the workpiece.

Safety: Eye protection: Always wear safety glasses or a face shield.

Workpiece clamping: Secure the workpiece firmly to the drill press table with clamps or a vise. Never hold the workpiece by hand. This prevents the workpiece from spinning and causing injury.

Chuck key: Always remove the chuck key from the chuck immediately after tightening or loosening the drill bit. Leaving the chuck key in the chuck is a major safety hazard.

Clothing and jewelry: Avoid loose clothing, jewelry, and long hair that could get caught in the rotating parts of the drill press.

Operation: Starting: Ensure the power switch is off. Select the appropriate drill bit and securely tighten it in the chuck using the chuck key. Set the correct speed for the material being drilled. Secure the workpiece to the drill press table. Put on your safety glasses or face shield. Turn on the drill press.

Drilling: Lower the drill bit slowly and steadily into the workpiece. Apply light, even pressure. Use cutting fluid (lubricant) when drilling metal to reduce friction and heat.

Chip Removal: As you drill, periodically retract the drill bit to clear away chips. This prevents the drill bit from binding and breaking.

Stopping: Turn off the drill press and allow the drill bit to come to a complete stop before removing the workpiece.

Maintenance: Lubrication: Regularly lubricate the spindle and quill with machine oil. This will help to ensure smooth operation and prevent wear.

Cleaning: Regularly clean the drill press to remove metal chips and debris. Use a brush or vacuum cleaner.

Belt Tension: Check the belt tension regularly and adjust as needed. Loose belts can cause the drill press to vibrate and reduce its cutting power.

Chuck Cleaning and Lubrication: Clean the chuck regularly with a wire brush and lubricate it with a light oil. This will help to ensure that the drill bit is held securely.

Example 1: Grinding a Chisel A learner is tasked with sharpening a cold chisel on a bench grinder.

Safety First: The learner puts on safety glasses and checks that the wheel guards are properly adjusted.

Tool Rest Adjustment: The tool rest is adjusted to within 3mm of the grinding wheel.

Grinding: The chisel is held firmly against the tool rest at the correct angle. Light, even pressure is applied. The chisel is moved back and forth across the wheel.