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MENG 1005: Workshop Technology > GRINDING > Flashcards

GRINDING Flashcards

1
Q

What are the characteristics of a grinding abrasive?

A

The abrasive must be:
* Harder than the material being ground
* Strong enough to withstand grinding pressures
* Heat-resistant to avoid it becoming dull at grinding temperatures
* Friable so that when the cutting ede becomes dull it will break off leaving behind a new sharp surface

Friable means that the material is capable of fracturing.

The fracturing action reduces the heat of friction, producing relatively cool-cutting.

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2
Q

What are the abrasice classes?

A
  • natural abrasive
    *
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3
Q

What are some examples of natural abrasives?

A

Examples of natural abrasives are:
* Sandston
* Garnet
* Flint
* Emery
* Quartz
* Corundum

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4
Q

What is aluminium oxide used for?

A

Aluminium oxide is one of the most abrasive materals used for gridning and it is used for high-tensile-strength materials.

Aluminium oxide makes up 75% of grinding wheels. It is manufactured with various degrees of purity [as purity increases so does the hardness and brittleness of the material].

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5
Q

What is the use of silicon carbide?

A

Silicon carine is used for grinding materials which have a low tensile strength and high density.

Siliconcarbide is harder and touger than aluminium ooxide

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6
Q

What is the use of cubic boron nitride?

A

Boron carbide is the hardest material manufactured with the exeption of diamond. However, it is not susitable for use in gridning wheels. Boron nitride is only used as a loose abrasive and as a cheap substitute for diamond dust, ultrasonic machining applications and in the manufacture of precision gauges and sand blast nozzels.

Diamond dust is a glittering material that can be applied to paper and ink in the silkscreen printing process to create a textured and luminous finish

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7
Q

WHat are some diamond types?

A
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8
Q

What are the basic functions of a grind wheel?

A

generation of cylindrical, flat and curved surfaces
removal of stock
production of highly finished surfaces
cutting-off operations
production of sharp edges and points

need to maintain material temperature w hile grinding

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9
Q

What are abrasive grains?

A
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10
Q

What are some grain sizes adn what are they used for?

A
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11
Q

WHat hold the grain tgether?

A
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12
Q

What factors must be considered when selecting grain sizes?

A

type of finishe desired
type of material being ground
amount of material to be removed
area of contact between wheel and workpiiece

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13
Q

WHat are the six common bond types?

A

when mixing concrete the grain is the stone and the bond is the cement

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14
Q

What is the grade of a bond?

A

Grade is defined as the degree of strength with which the bod between the particle

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15
Q

What factors must be considered when selecting grain grade?

A

hardness of material

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16
Q

WHat ismeant by the structure of the grain?

A
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17
Q

WHat ae the factors which affect

A
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18
Q

How are grinding wheels manufactured

A
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19
Q

WHata re the main operations in manufacture of vitrified grind wheel?

A
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20
Q

How do you mount a grinding wheel onto your machine?

A
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21
Q

What precautons must be taken when handling and storing the grind whell?

A
22
Q

Whata re soem wheel grade fauts?

A
23
Q

WHat are some signs that yur grinding wheel is too sooft?

A

bthe wheel breaks down too fast
poor surface finish
cuts

what tool is used to clean a grinding wheel?

24
Q

WHat are some signs that your grinding wheel is toohard?

A
25
Q

WHare three types of bond for diamond wheels?

A
26
Q

WHat are the general guidlines for sing a CBN grinding wheel?

A

sselect bond

27
Q

Why are natural abrasives hardly used for grinding?

A

Natural abrasives are hardly used for grinding in modern times as their grain size, shape and purity can not be closely controlled like with manufactured abrasives.

28
Q

What are some examples of manufactured abrasives?

A

Some examples of manufactured abrasives are:
* Aluminiumoxide
* Silicon carbide
* Boron carbide
* Cubic coron nitride
* Manufactured diamond

29
Q

What is green silicon carbide used for?

A

Green silicon carbide is used for grinding cemented carbides and other hard materials.

30
Q

What is black silicon carbide used for?

A

Black silicon carbide is used for grinding case iron and soft nonferrous metals and ceramics.

31
Q

What is zirconia-aluminium oxide and what is it used for?

A

Zirconia-aluminium oxide is made by fusing zirconium oxide and aluminium oxide asextremely high temperatures. It is used for heavy-duty rough and finish grinding in steel mills and welds and for snagging in foundries.

Zirconia-aluminium oxide was the first alloy abrasive produced. The alloy contains about 40% zirconia. It is stronger than standard aluminium oxide and lasts 2 to 5 times longer.

32
Q

What is cubic boron nitride?

A

Cubic boron carbide is a synthetic abrasive which has a hardness between silicon carbide and diamond. It is capable of ithstanding grinding temperatures up to 2500°F. It is used in cool-cutting and chemically resistant to all inorganic salts and organic compounds.

Cold cutting is used to cut a material without heat or producing sparks.

It was developed by General Electric Company in 1969. It is capable of maintaining very close tolerances.

33
Q

How are manufactured diaamonds made?

.

A

First success involved carbon and iron sulfide in granite tube closeed with tantalum disks at pressures of 66,536 and 750 psi and at a temperature of around 2250°F.

Temps are high to melt the C saturated metal and start diamond growth.

Manufactured diamonds were first produced by the General Electric Company in 1954 and became comercially avaiable in 1957. Industrial diamonds are referred to as bort.

34
Q

What are the diffferent types of diamonds?

A

The different types of diaonds are:

35
Q

What is the function of the grinding wheels?

A

The gridning whee l is used in:
* Generation of cylindrical, flat and curved surfaces
* Removal of stock
* Production of highly finished surfaces
* Cutting-off operations
* Production of sharp edges and points

36
Q

What does the grain on the grinding wheel do?

A

Each grain on the working surface of the grinding wheel acts as a seperate cutting tool removing small metal chips as it passes over the surface of the work.

37
Q

What are the different grain sizes?

A
38
Q

How is the grain sorted into its different sizes?

A

The abrsive ingot/pig/stock material is heated in an electric furnace and crushed into grains and cleaned. They are the ssorted b passing them through screens which contain a cerain number of meshes/opening per inch

39
Q

What are the commercial grain size classications?

A
40
Q

What are very coarse, coarse and medium grain sizes used for?

A

These grain sizes are used for rough grinding operations

41
Q

What are very medium, fine, very fine and flour size grain sizes, used for?

A

These grain sizes are used for precision grinding operations

42
Q

What are very flour size and beyond grain sizes, used for?

A

These grain sizes are used for ultra precision grinding operations between 2 to 4 micron finish or fine.

43
Q

What factors affect the selection of grain sizes?

A

The correct grain to be used ina grinding operation is dependent on:
* The type of finish desired
* The amount of material to be removed
* The area of contact between the grinding wheel and workpiece

44
Q

What are the six common bond types used in the manufacture of grinding wheels?

A

The six common bond types are:
* Vitrified
* Resinoid
* Rubber
* Shellac
* Silicate
* Metal

45
Q

What are grinding wheel bonds used for?

A

Grinding wheel bonds are used to hold abrasive grains together on the wheel.

46
Q

What is meant by the bond grade?

A

The bond grade refers to the degree of strength with which the bond holds abrasive particles in the bond setting

47
Q

What are the two bond grades?

A

The two types of bond grades are:
* Hard grade
* Soft grade

Hard grades hold grains when grinding & soft grades quickly release them

Wheel grade symbols range from A to Z. A is the softest grade while Z is the hardest.

48
Q

What factors determine which bond grade is chosen for a particular job?

A

The factors which bond type is to be used are:
* The hardness of the material to be grinded
* The condition of the machine
* The speed of the grinding wheel and workpiece
* The rate of feed of the workpiece onto the grinding wheel
* The operator characteristics

49
Q

What is meant by the structue of the grinding wheel?

A

The structure of the grdining wheel refers to the relationship between the grain and the void that seperate them from the bonding material.

50
Q

What is meant by dense and open grinding wheel structures?

A

Dense structures have close close grain spacing while open structures have relatively wide spacing.

The wheel structure used on a worpiece depends on the type of work required.

MENG 1005: Workshop Technology (9 decks)

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