40 Questions
What is the primary reason why dull wheels are problematic?
They require more pressure, leading to potential wheel explosion
What is the recommended maximum gap for the tool rest on a bench or pedestal grinder?
1/8 inch
What should you do when setting up a new wheel on a grinder?
Position the wheel no more than 1/16 inch away from the wheel periphery
What is the typical grit size of the wheel on the right-hand side of a bench mounted grinder?
120-180 grit
Why should you stand to one side of the grinder upon start-up?
To avoid being hit by stony chunks in case the wheel explodes
What should be checked for damage before using a grinder?
The electrical cables
Why should you apply gradual pressure when using a grinder?
To allow the wheel to warm up evenly
What is the typical diameter of the wheel on a bench mounted grinder?
8-10 inches
What is the average RPM of a common wheel?
3600
What is the primary use of a pedestal grinder?
Snagging and removing large amounts of materials
What is the advantage of using a side grinder?
Ability to sharpen on a flat face
What is the purpose of coarse grit wheels?
Roughing operations
What type of wheel is used to grind non-ferrous materials?
Silicon Carbide Wheels
What is the consequence of grinding non-ferrous material on an Aluminum Oxide Grinding Wheel?
The wheel will break or crack
What is the characteristic of a fine grit wheel?
Small pieces of grit
What is the diameter range of a pedestal grinder wheel?
10-24 inches
What is the primary factor that determines the hardness of a grinding wheel?
Bonding agent used to hold the grit
What is the advantage of using a soft-bonded grinding wheel?
It allows for freer cutting action and cooler work pieces
What should be done before turning on the grinder after installing a new wheel?
Tighten the fasteners
What is the purpose of a wheel blotter?
To take up the space between the wheel and the motor shaft
Why is it necessary to perform a ring test on new wheels?
To detect cracks in the wheel
What type of thread is used on the right side of the grinder?
Right-hand thread
What is the result of using a hard-bonded grinding wheel?
The wheel lasts longer and may be more economical
What should be checked before installing a new wheel on the grinder?
The wheel's appropriate blotters
What is the result of a loaded grinding wheel?
Poor performance and an increase in pressure required to grind
Why is wheel dressing necessary?
To remove the top surface of the grinding wheel periphery
When should wheel dressing be performed?
When the wheel looks glazed, is not cutting freely, or appears loaded
What is the purpose of truing a grinding wheel?
To ensure the wheel is running true to the axis of the spindle
What causes a grinding wheel to become loaded?
Grinding non-ferrous materials and using wheels that are too hard
What is used to true a grinding wheel?
A diamond tip
What is the result of not truing a grinding wheel?
Increased vibration throughout the grinder
What should be done after truing a grinding wheel?
Stop the grinder and readjust the tool rest to a 1/16” distance
What is the primary function of wheel flanges?
To provide a cushioning area for the wheel
What should be checked on the wheel flange during inspection?
Nicks and marks on the surface of the flange
What is the purpose of wheel bushings?
To take up the space between the spindle and wheel
What is the consequence of a glazed wheel?
The wheel bonding material wears away faster
Why should the initial tensioning of the wheel spindle not be overly tightened?
To prevent wheel breakage
What should be used to provide rotational locking during the tightening operation of the wheel spindle?
A wooden stick
Why should blotters be in place on both sides of the wheel?
To ensure proper mounting of the wheel
What type of thread is used on the left-hand side of the spindle?
Left-hand thread
Study Notes
Safety Procedures
- Fasten pedestal and bench grinders securely to a solid surface to prevent movement during operation.
- Ensure all guards are in place and secure before using a grinder.
- Check electrical cables for damage from metal debris and sparks, and poor connections.
- Stand to one side of the grinder upon start-up and until the wheel reaches operating speed before engaging in work.
- Apply gradual pressure to allow the wheel to warm up evenly, as dull wheels can cause excessive pressure.
Grinder Safety
- The tool rest on any bench or pedestal grinder must not exceed 1/8” gap (OH&S).
- When setting up a new wheel, it should be no more than 1/16” away from the wheel periphery.
Grinder Types
- Bench Mounted Grinder:
- Typical wheel size: 6, 8, 10 inches in diameter.
- Wheel grits: coarse (60-80) on the left-hand side and fine (120-180) on the right-hand side.
- Common wheel width: 1 inch.
- Average RPM: 3600.
- Used for finish or general-purpose shop type applications.
- Pedestal Grinder:
- Wheel diameter: 10-24 inches.
- Wheel width: 1-3 inches.
- Maximum RPM: 1800.
- Used for snagging, removing large amounts of material, and rough grinding operations.
- Side Grinders:
- Designed to grind on the face of the wheel.
- Special wheels with steel backing plates are required.
- Advantage: tools can be sharpened on a flat face rather than the periphery of a round wheel.
Wheel Selection
- Grinding wheels are available in various grit sizes.
- Lower grit numbers (36-80) are used for roughing operations, while higher grit numbers (100-240) are used for finish operations.
- Wheel types:
- Aluminum Oxide Wheels: for ferrous materials, not for non-ferrous materials.
- Silicon Carbide Wheels: for non-ferrous materials, such as sharpening carbide cutting tools, brass, and bronze.
Wheel Mounting
- Wheel installation:
- Check for wheel appropriate blotters.
- Check the wheel fit.
- Tighten fasteners before turning the grinder on.
- Manually spin the wheel to ensure it spins freely.
- Wheel spindles:
- Left-hand thread on the left-hand side of the spindle.
- Right-hand thread on the right-hand side of the spindle.
Wheel Safety
- Ring test: new wheels must be tested for cracks.
- Ensure correct plastic wheel bushings are used.
- Wheel blotter:
- Check the blotter glued to the wheel to ensure the machine's RPM is slower than the grinding wheel's maximum RPM.
- Blotters must be in place on both sides of the wheel prior to mounting.
- Wheel flange inspection:
- Check for nicks and marks on the surface of the flange.
- Flanges must contact the blotter.
Wheel Maintenance
- Dressing and truing:
- Glazed wheel: a condition where the wheel takes on a glass-like appearance, caused by grain wearing away faster than the wheel bonding material.
- Loaded grinding wheel: when workpiece chips adhere to the cutting face of the wheel, caused by grinding non-ferrous materials and wheels that are too hard.
- Wheel dressing: removes the top surface of the grinding wheel periphery to expose new grit.
- Truing a wheel: performed when an out-of-round wheel causes a vibration throughout the grinder, ensuring the wheel is running true to the axis of the spindle.
Grinding Operations
- Pedestal grinder operations:
- Grinding a prick or center punch.
- Repairing a flat screwdriver.
- Drill bit sharpening.
This quiz assesses knowledge on safety precautions when operating hand grinding machines. It highlights a scenario where a worker's life is at risk due to incorrect adjustment of the grinder, leading to devastating consequences.
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