Chapter 11: Knowledge Check

Check Your Knowledge: Chapter 11

Quiz yourself using the following chapter review questions to check how well you can recall the material.

Review Questions

1. True or false: Precision grinding is typically the final operation for parts.
2. Use the correct term to complete the sentence. The process that utilizes a rotating disc embedded with abrasive particles that gradually wears down the material, ensuring precise thickness and a refined finish, is referred to as __________.
3. True or false: After adjusting the height of the wheel, feed the part into the grinding wheel against its rotation. Typically, from left to right.
4. To use a vertical grinder, or to use a horizontal grinder? That is the question… : Accordian
   1. Horizontal (Surface) Grinder vs. Vertical (Blanchard) Grinder: Wheel Orientation
   2. Contact Dynamics During Grinding
   3. Application Differences
5. True or false: The workpiece rotates against the grinding wheel as it turns on a cylindrical, or vertical grinder.
6. This shape of grinding wheel is the most common used for grinding.
   1. Straight
   2. Cupped
   3. Recessed
   4. None of the above
7. Abrasive selection: Accordian:
   1. Best Abrasive for Grinding Steel
   2. Best Abrasive for Grinding Iron Parts
   3. Best Abrasive for Carbide Tooling
8. How does the grain size, or grit affect the process of grinding?: Accordian:
   1. What grit size would be best for removing a significant amount of material?
   2. When finished grinding, choose a grit size in this range to obtain a fine surface finish.
   3. If the material being ground is soft, use a grit in this range.
   4. If the material being ground is hardened, choose a grinding wheel with this grit size.
9. True or false: A soft grade of wheel should be used when grinding hard material.
10. If a grinding wheel makes a high “ring” sound when performing a ring test, which of the following is understood? Choose the best answer.
    1. The wheel has been used before
    2. There is a crack in the wheel
    3. There are no fractures in the wheel. This wheel will cut.
    4. All of the above
11. True or false: When using a magnetic chuck with parts that are non-magnetic, blocks can be placed around the part to keep it from moving.
12. What must be done to the grinding wheel before starting to ensure it runs true and accumulated deposits are removed?
    1. Performing a ring test
    2. Giving it to someone else
    3. Dressing the wheel
    4. Dropping the wheel on the floor
13. True or false: Carefully bringing the wheel, when not spinning, down to the top of the part is called touching off the wheel.
14. Problems that may be encountered: Accordian:
    1. Burning is the dark discoloration of the part when excessive heat is present. What are some of the contributing factors that cause Burning?
    2. What may contribute to Scratches in the part?
    3. Chatter will leave the part looking like the beach when the tide goes out. See fig 11.18 What might have caused this?
15. Before actually grinding, certain steps need to be taken before starting. Pick the best answer below that describes the process, and why it is important.
    1. Perform the ring test before mounting the wheel on the grinder
    2. Hold on tight
    3. Dress for success
    4. All of the above

Answer Key

1. True – Yes, Grinding will achieve high tolerance, and quality finishes if done properly.
2. grinding – Yes, Grinding takes various forms. The constant is a rough surface, like a grinding wheel, spinning at a high rpm, osculating over a surface to remove small amounts of material to attain a quality precision, and finish.
3. True – Yes, Just like rough cutting on a manual mill. This would be the same as a conventional cut. Retract along the X axis, adjust the position on the Y axis, and make another pass, left to right.
4. Accordian Answers:
   1. On a horizontal grinder, the outside edge of the grinding wheel is used to remove material. With a vertical grinder, the side of the wheel is used to remove material.
   2. The contact of a horizontal grinding wheel is a line that is the width of the wheel. The contact of a vertical grinding wheel is the complete side of the wheel.
   3. Because of the small contact area, a horizontal grinder will be good for small parts, and intricate features. The large contact area on the vertical grinder will be good for large flat areas.
5. True – Yes. The part rotates while being ground on a vertical, or cylindrical grinder. The vertical grinder uses the face of the wheel for large flat surfaces. The cylindrical grinder uses the outer diameter of the wheel to grind the OD, or ID of a part.
6. Straight – Yes, This is the most common shape of a grinding wheel.
7. Accordian Answers:
   1. Grinding wheels made with Aluminum Oxide are used on steel parts. Steel is an alloy that contains carbon. The carbon makes it harder, and stronger than iron parts.
   2. Ceramic Aluminum Oxide grinding wheel is best used on iron parts. It will be durable, and provide a fine surface finish.
   3. Commonly referred to as a Green wheel, the Silicon Carbide wheel is used for modifying carbide tooling, or grinding on carbide parts.
8. Accordian Answers:
   1. A low number grit size, 36 or 60, would be good to remove significant material in a short amount of time. The resulting finish will be rough.
   2. Using a 100, or 150 grit wheel will result in a high quality finish.
   3. ill allow the material to leave the wheel when grinding. If the grit is too small, the material will adhere to the wheel. This will  plug up the grain structure, and build up unwanted heat.
   4. Hard metals will benefit from a wheel with a fine grit pattern. A 150 grit size will offer more cutting points for removing material.
9. True – Yes, The soft wheel will break down when grinding. This will release the dull grains, and expose new sharp grains.
10. There are no fractures in the wheel. This wheel will cut. – Yes. A wheel with a crack, or fracture may explode during grinding. This wheel may be loaded. Tighten the nut in the opposite direction of the wheel spin, and prepare to start grinding.
11. True – This is called Blocking. Ensure that the blocks are lower than that of the material being ground.
12. Dressing the wheel – Yes, Use a diamond dressing tool positioned behind the center of the wheel on the outgoing nip side. This will keep it from jamming into the wheel, and causing damage
13. True – This will set the wheel within .003 of the part when using paper to touch it off. Then the part can be moved out from under the wheel, and the wheel started.
14. Accodian Answers:
    1. Overly aggressive cuts, lack of sufficient coolant, not dressing the wheel before grinding to remove deposits, or choosing a wheel that is too hard for the material.
    2. Grinding without coolant, not cleaning the table, or not dressing the wheel before grinding can leave unwanted scratches in the part.
    3. Chatter, or waviness can result from a wheel that is not properly tightened on the arbor. A loose wheel will move and “bounce” when grinding the part. Chatter can also result from not dressing the wheel to ensure that it is running true. Picture trying to grind with an egg shaped wheel.
15. All of the above – Yes. All of the above are critical steps in preparing to grind a part. Skipping any one of them may result in undesirable consequences.