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Machine Safety: Preventing Grinding Wheel Accidents
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Machine Safety: Preventing Grinding Wheel Accidents

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Questions and Answers

What is the primary reason why dull wheels are problematic?

  • They are more difficult to handle
  • They produce less precise grinding
  • They are more expensive to replace
  • They require more pressure, leading to potential wheel explosion (correct)
  • What is the recommended maximum gap for the tool rest on a bench or pedestal grinder?

  • 1/2 inch
  • 1/16 inch
  • 1/8 inch (correct)
  • 1/4 inch
  • What should you do when setting up a new wheel on a grinder?

  • Check the electrical cables for damage after setting up the wheel
  • Stand directly in front of the grinder when starting it up
  • Position the wheel no more than 1/16 inch away from the wheel periphery (correct)
  • Apply heavy pressure to test the wheel
  • What is the typical grit size of the wheel on the right-hand side of a bench mounted grinder?

    <p>120-180 grit</p> Signup and view all the answers

    Why should you stand to one side of the grinder upon start-up?

    <p>To avoid being hit by stony chunks in case the wheel explodes</p> Signup and view all the answers

    What should be checked for damage before using a grinder?

    <p>The electrical cables</p> Signup and view all the answers

    Why should you apply gradual pressure when using a grinder?

    <p>To allow the wheel to warm up evenly</p> Signup and view all the answers

    What is the typical diameter of the wheel on a bench mounted grinder?

    <p>8-10 inches</p> Signup and view all the answers

    What is the average RPM of a common wheel?

    <p>3600</p> Signup and view all the answers

    What is the primary use of a pedestal grinder?

    <p>Snagging and removing large amounts of materials</p> Signup and view all the answers

    What is the advantage of using a side grinder?

    <p>Ability to sharpen on a flat face</p> Signup and view all the answers

    What is the purpose of coarse grit wheels?

    <p>Roughing operations</p> Signup and view all the answers

    What type of wheel is used to grind non-ferrous materials?

    <p>Silicon Carbide Wheels</p> Signup and view all the answers

    What is the consequence of grinding non-ferrous material on an Aluminum Oxide Grinding Wheel?

    <p>The wheel will break or crack</p> Signup and view all the answers

    What is the characteristic of a fine grit wheel?

    <p>Small pieces of grit</p> Signup and view all the answers

    What is the diameter range of a pedestal grinder wheel?

    <p>10-24 inches</p> Signup and view all the answers

    What is the primary factor that determines the hardness of a grinding wheel?

    <p>Bonding agent used to hold the grit</p> Signup and view all the answers

    What is the advantage of using a soft-bonded grinding wheel?

    <p>It allows for freer cutting action and cooler work pieces</p> Signup and view all the answers

    What should be done before turning on the grinder after installing a new wheel?

    <p>Tighten the fasteners</p> Signup and view all the answers

    What is the purpose of a wheel blotter?

    <p>To take up the space between the wheel and the motor shaft</p> Signup and view all the answers

    Why is it necessary to perform a ring test on new wheels?

    <p>To detect cracks in the wheel</p> Signup and view all the answers

    What type of thread is used on the right side of the grinder?

    <p>Right-hand thread</p> Signup and view all the answers

    What is the result of using a hard-bonded grinding wheel?

    <p>The wheel lasts longer and may be more economical</p> Signup and view all the answers

    What should be checked before installing a new wheel on the grinder?

    <p>The wheel's appropriate blotters</p> Signup and view all the answers

    What is the result of a loaded grinding wheel?

    <p>Poor performance and an increase in pressure required to grind</p> Signup and view all the answers

    Why is wheel dressing necessary?

    <p>To remove the top surface of the grinding wheel periphery</p> Signup and view all the answers

    When should wheel dressing be performed?

    <p>When the wheel looks glazed, is not cutting freely, or appears loaded</p> Signup and view all the answers

    What is the purpose of truing a grinding wheel?

    <p>To ensure the wheel is running true to the axis of the spindle</p> Signup and view all the answers

    What causes a grinding wheel to become loaded?

    <p>Grinding non-ferrous materials and using wheels that are too hard</p> Signup and view all the answers

    What is used to true a grinding wheel?

    <p>A diamond tip</p> Signup and view all the answers

    What is the result of not truing a grinding wheel?

    <p>Increased vibration throughout the grinder</p> Signup and view all the answers

    What should be done after truing a grinding wheel?

    <p>Stop the grinder and readjust the tool rest to a 1/16” distance</p> Signup and view all the answers

    What is the primary function of wheel flanges?

    <p>To provide a cushioning area for the wheel</p> Signup and view all the answers

    What should be checked on the wheel flange during inspection?

    <p>Nicks and marks on the surface of the flange</p> Signup and view all the answers

    What is the purpose of wheel bushings?

    <p>To take up the space between the spindle and wheel</p> Signup and view all the answers

    What is the consequence of a glazed wheel?

    <p>The wheel bonding material wears away faster</p> Signup and view all the answers

    Why should the initial tensioning of the wheel spindle not be overly tightened?

    <p>To prevent wheel breakage</p> Signup and view all the answers

    What should be used to provide rotational locking during the tightening operation of the wheel spindle?

    <p>A wooden stick</p> Signup and view all the answers

    Why should blotters be in place on both sides of the wheel?

    <p>To ensure proper mounting of the wheel</p> Signup and view all the answers

    What type of thread is used on the left-hand side of the spindle?

    <p>Left-hand thread</p> Signup and view all the answers

    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.

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    Description

    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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