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1st Year Sheet Metal > Workplace Theory > Flashcards

Workplace Theory Flashcards

1
Q

Stepstools

A

Lightweight, sturdy and compact. You can stand on top of stepstool

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2
Q

Portable work stand

A

Sawhorses, or material supports. A 2 foot model can be used as a step stool.

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3
Q

Single stepladders

A

Most popular used for low or medium heights.

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4
Q

Double or twin stepladders

A

Allows two people to work on them

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5
Q

Platform ladders

A

Has regular steps and a large standing surface a couple rings up.

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6
Q

Single ladder

A

Single section non extendable ladder. Mid range height and ideal for repeated tasks at a constant height

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7
Q

Extension ladder

A

Handle a wide range of tasks at varying elevations and are most popular long ladder.

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8
Q

Things to consider when choosing a ladder.

A

Your height
Height you want to reach
Style of ladder

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9
Q

You can stand on top two rungs of ladder

A

False

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10
Q

Ladder ratings

A

Super heavy duty 375 lbs
Extra heavy 300
Heavy duty 250
Medium duty 225

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11
Q

What are ladders made of and uses

A

Wood- non conductive when clean and dry
Aluminum- string, light weight, and corrosion resistant
Fiberglass- electrically non conductive and strong

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12
Q

4 to 1 ladder ratio

A

4 meters of length needs 1m of setback and 1m above roof.

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13
Q

Stepladders use a 6 to one ratio for each side

A

True

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14
Q

What are scaffolds

A

Temporary elevated work platforms and supporting structures

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15
Q

The load of a scaffold must be known and static.

A

True

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16
Q

What is frame scaffold?

A

Most widely used, is a welded assembly of tubular members joined with cross races, connecting pins, bases, brackets, and guardrails.

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17
Q

Most common frame widths and heights?

A

3’ and 5’ are common widths and 5’ and 6’6 are common heights.

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18
Q

What is tube and coupler scaffold?

A

Also called tube and clamp is flexible and versatile in providing access and design freedom.

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19
Q

What is modular system scaffold?

A

Similar to tube and clamp but much easier to assemble.

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20
Q

Suspended scaffold?

A

Platforms supported by wire.

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21
Q

What is the max height and load of a scaffold?

A

It can not be more than 3 times the height of the smallest dimension of its base.
The scaffold must be strong enough to hold 4 times the imposed load.

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22
Q

When must a scaffold be tied in?

A

Every 4.6 meter vertical and 6.4 meter horizontal.

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23
Q

Explain scaffold guardrails?

A

Consists of guardrail posts, the guardrail, the midrail, and a toebord if needed.

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24
Q

Five factors to consider when choosing a scaffold?

A 
Availability
Cost
Workforce expertise
site parameters
Expected loads, terrain
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25
Q

What is rigging?

A

It is the bringing together of various lifting devices to raise or lower materials or equipment.

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26
Q

Fiber rope?

A

It is made of Manila, sisal, cotton, or coir. It can be twisted or braided

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27
Q

Nylon ropes provide the greatest strength and is approximately 2.5 times stronger than manila

A

True. It is also resistance to moisture and rot.

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28
Q

How to determine rope load strength?

A

5 to 1 for new rope or 10 to 1 for an older rope

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29
Q

What is a bowline knot?

A

It is used for hoisting safety lines and for hitching around posts and rings.

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30
Q

Figure 8 knot?

A

Used for tying two rope ends that are equal diameter.

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31
Q

Sheepshank knot?

A

Used to shorten up excessively long ropes that may pose a tipping hazard.

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32
Q

Sheet bend (single or double)

A

Used to join lightweight to medium weight ropes of two different diameters.

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33
Q

What are slings?

A

Hardware components that are used to fasten loads to hitting equipment for the purpose of safely moving loads to the elevations.

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34
Q

Slings should not be used at less than 60 degree angles

A

True

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35
Q

The lower the number gauge wire the more snps it can hold.

A

True

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36
Q

Heavy duty drills usually have a chuck capacity of 12mm or 1/2” and larger.

A

True. Smaller drills 1/4” and 3/8” may have a keyless chuck.

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37
Q

Another name for angle drills?

A

Hole saws.

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38
Q

What are twist drills?

A

Also known as drill bits consist of 3 main parts: the shank, the body, and the point. They can be designated by number, letter, or metric units.

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39
Q

What are two types of shanks on a twist drill?

A

Taper shanks and straight shanks. Straight shanks are held in a Jacob’s chuck and are used on drills up to 1/2” diameter. Taper shanks are used on drills larger than 1/2” diameter. All taper shank drills have a morse taper that fits in a morse chuck.

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40
Q

What are helical flutes on the body of a twist drill?

A

These are grooves that carry chips up and out of the hole.

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41
Q

The point of the twist drill is where all the cutting takes place. The chisel edge is the portion remaining between flutes. It does not cut and should be as small as possible.

A

True

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42
Q

What should the drill point angle be?

A

118 degrees and a lip clearance of 10 degrees

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43
Q

How do concrete and masonry bits differ from regular bits?

A

These bits have a carbide tip that is strong enough to take the scraping and hammering action of drilling into hard materials without chipping and shattering.

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44
Q

What are unishears?

A

These are hand power shears used to cut metal. The metal on one side of the cut line has to be moved out of the way of the shear, leaving that piece distorted.

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45
Q

What are niblers?

A

These use a punching action that punches out small squares of metal. The pinching action leaves the metal undistorted kn both sides of the cut line.

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46
Q

Double cutting shears?

A

They make two cuts in the metal leaving a small strip of waste.

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47
Q

What are the capacities for a standard hand brake?

A

Ranges from 22 gauge mild steel to 12 gauge mild steel.

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48
Q

Box and pan break?

A

The fingers offer the ability to form a box or pan from one piece of metal. The fingers of the box and pan must be properly seated in the top leaf to avoid damage to the break.

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49
Q

Operating procedures of a box and pan break

A

Never bend band iron, rod, or wire. Use the middle of the break to equalize the strain on the break for shorter pieces.

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50
Q

What is an electromagnetic brake?

A

Also called a megnabend uses electricity to produce a magnetic force to bring down clamping members, known as keepers, on to the metal to make complex shapes that are not possible in a standard brake or box and pan brake.

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51
Q

What is a squaring shear?

A

Foot shear. Squaring shears are equipped with gauges, which are used as stops. These include a back gauge, side gauges, front gauge, and a bevel gauge.

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52
Q

What is a noyes groover?

A

Floor machine used to finish groove sensor various sizes much quicker than working by hand.

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53
Q

Describe a di-acro hand manual bender?

A

Used to bend various diameters of tubing and solid round bar stock up to 1” round mold steel. Can also bend square tubing, flat bar, angle iron and channel.

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54
Q

Senistive drill press

A

Floor drill press for small, precise work.

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55
Q

Cutting speeds and feeds of twist drills

A

Cutting speed is the rate at which the cutting edge of a tool moves through metal ,measured in feet per minute. Cutting fluids will reduce the heat causing the tool to be used at a higher speed.

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56
Q

Horitzontal band saws.

A

Only straight cuts. Are sized by the largest piece of material they can cut.

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57
Q

What is a contour band saw?

A

Also called a vertical band saw. Mainly used for shapingmetal rather than cutting length of stock. Can cut complex shapes.

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58
Q

Describe pedestal grinders.

A

Sometimes called floor grinders. Wheel guards should extend 30° to 45° past the vertical. Tool rests should be mounted so that there is no more than 3mm (1/8”) between the grinding wheel and the tool rest and aligned so that the surface is 1/4” to 1/2” below the center of the grinding wheel.

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59
Q

What are blotters (grinding wheel).

A

They are a heavy piece of paper attached to each side of the grinding wheel. They protect the flanges from the abrasive grit of the wheel. They also compensate for uneven surfaces of the wheel, and they have important info on them.

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60
Q

What is dressing and truing of grinding wheels.

A

Dressing is the operation of cleaning or restoring the sharpness of a wheel that has become glazed or loaded with foreign particles. Truing is the removal of material.

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61
Q

Purpose of a press break.

A

Also known as a power break it utilizes various types of punches or dies to form the metal.

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62
Q

Explain spot welders.

A

The pressure is maintained after the current is shut off until the weld has cooled and solidified. This process is called resistance welding. A reasonable tip diameter is 1/8” plus two metal thicknesses.

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63
Q

What is the difference between pipe wrench and spud wrench?

A

Spud wrenches have smooth jaws.

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64
Q

Scratch awl .just be sharpened to 15°.

A

True

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65
Q

What is the cutting capacity of aviation snips?

A

18 gauge. Bulldog snips can cut up to 16 gauge.

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66
Q

What are duckbill snips?

A

These are big snips that can cut radius curves

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67
Q

How do you order hacksaw blades?

A

They come in different teeth per inch (tpi) and come in 14, 18, 24, or 32 tpi.

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68
Q

What is the best cutting angle for a chisel?

A

60°

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69
Q

What are the point angles of a center punch and a prick punch?

A

Center punch has an included angle of 90° while a prick punch is ground to an included angle of 30°.

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70
Q

Difference between a riveting and setting hammer?

A

Riveting hammer has a curved face and the peen end is double tapered. A setting hammer (tin hammer) has a square face on one end and a peen end that is tapered on one side only.

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71
Q

Mallets are used for shrinking metal.

A

True. When turning an edge inward on a sheet metal project, the metal must be shrunk.

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72
Q

Cabinet tip screwdriver.

A

Differs from a standard slot top because it is parallel from the tip back to allow access to recessed holes.

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73
Q

Rivet sets.

A

Used to hammer down Pittsburgh seams.

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74
Q

Metals such as gold, silver, copper, and aluminum in their pure form are called what?

A

Metallic elements. When a metal contains a combination of two or more metals it is then considered an alloy.

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75
Q

What is expanded metal?

A

Also known as expanded mesh is made from solid sheets of metal that are simultaneously split and expanded in an operation that forms diamond shaped openings.

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76
Q

What is perforated metal?

A

It starts as solid sheets, which are then punched with holes. Perforated metal is commonly used in sheet metal for sound attenuation.

77
Q

What is another name for hardware cloth?

A

Bird screen.

78
Q

What are the 8 properties of metal?

A 
Brittleness
Conductivity
Ductility
Elasticity
Hardness
Malleability
Strength
Toughness
79
Q

What is brittleness in metal?

A

This is the ability to withstand distortion. Glass and cast iron are brittle as they will shatter easily.

80
Q

Most metals are considered good conductors because they permit the flow of heat or electricity very easily.

A

True. Copper is an excellant conductor of both heat and electricity.

81
Q

Explain the properties of a ductile metal.

A

It has the ability to withstand stretching, bending, or twisting past its elastic limit without breaking or losing any other mechanical properties. Mild steel and copper are examples of ductile metals.

82
Q

What is elasticity?

A

It is the tendacy of a metal to return to it’s original shape after forces have caused the metal to become deformed.

83
Q

What is hardness of metal?

A

The ability to resist forces that tend to push the molecules apart. Metal is hard when it resists penetration, scratching, cutting action and wear. Tempered steel used to make scratch awls is considered hard.

84
Q

Define malleability in metal.

A

Has the ability to withstand mechanical processing such as rolling, forging, and hammering without cracking or breaking. Malleability and ductility go hand and hand. Copper is very malleable.

85
Q

Describe the strength of metal.

A

Strength is the amount of high, steady stress a metal can withstand before it yields. Metals obtain their strength from the certain elements that are in them or from the way they are manufactured. Stainless is very strong.

86
Q

Explain toughness of metal.

A

The ability of a metal to withstand an impact load. Tough metal will not break or shear easily and will stretch without breaking. Titanium is very tough.

87
Q

What are the three categories of heat treating metal?

A

Annealing
Quenching
Tempering

88
Q

What is the process of annealing?

A

It is used to release internal stress in hardened metal. When metals are worked and formed by hammering and rolling, they become hardened. The process involves heating the metal to a pre-determined temperature and then allowing it to cool.

89
Q

The process of quenching metal?

A

This involves rapid cooling of a metal that is heated by immersion in a medium such as water or oil. This process usually hardens steel and creates internal stress, however, copper, silver, and certain alloys are rendered softer and more malleable by quenching.

90
Q

What is tempering metal?

A

Tempering is increasing the toughness and decreasing hardness in hardened steel by reheating to a temperature below transformation range, holding that particular temperature for a suitable time and then cooling at a suitable rate. Not attempted usually at a sheet metal shop.

91
Q

Practically all the work that is done to metal in a sheet metal shop is called what?

A

Cold worked.

92
Q

When does oxidation occur?

A

When a metal is exposed to the oxygen in the atmosphere. Every metal forms some kind of oxide on it and each oxide has different characteristics.

93
Q

Stainless steel have the addition of chromium to protect the surface.

A

True

94
Q

What is galvanic action?

A

This is a corrosive process that results when dissimilar metals come in contact with an electrolyte such as moisture.

95
Q

How can you prevent galvanic action?

A

Provide a barrier between the two metals.

96
Q

Describe metal gauging?

A

The thickness of metal is the gauge. Ferrous metals or metals with iron are gauged using the US standard gauge while non-ferrous metals are gusted using the American standard wire gauge, also known as the brown and Sharpe gauge.

97
Q

Metals are broken into two basic groups. What are they?

A

Ferrous and non-ferrous. If a metal contains iron, it is considered a ferrous metal.

98
Q

Steel is an alloy primarily composed of iron with a carbon content between 0.02% and 1.7% by weight depending on the grade.

A

True.

99
Q

Explain black iron.

A

This is the name given to uncoated mild steel sheets or coils and may be obtained as either hot rolled or cold rolled.

100
Q

What is steel plate?

A

Black iron that measures more than 1/8” is called steel plate.

101
Q

When welding zinc coated sheet, ventilation of the zinc oxide fumes is crucial to prevent an illness know as the zinc chills or metal fume fever.

A

True. Another disadvantage of zinc coated metal is that it must not be used on any food equipment because the zinc and its compounds are poisonous.

102
Q

Galvanized iron is a mild sheet that is coated with a thin layer of zinc.

A

True.

103
Q

What are two processes to make galvanized iron?

A

Hot dip galvanizing and electrogalvanizing. Steel sheets that have zinc added to them by electrogalvanizing go by the trade name satincoat, paintlock, and wipe coat..

104
Q

How do you gauge galvanized iron?

A

It is done by the US standard gauge. You have to take into account the thickness of the zinc coating. A 26 gauge of galvanized iron will be thicker than 26 gauge black iron.

105
Q

What is galvalume?

A

A zinc aluminium alloy coating with superior corrosion and resistance for applications without severe forming. Used in b vent.

106
Q

Explain stainless steel.

A

It is corrosion resistance. One of the most common types of stainless is type 304 of the basic 18-8 group which contains 18% chromium, 8% nickel, .08% carbon and the rest of steel. No 4 finish is common for restaurants. Has a high resistance to heat and corrosion.

107
Q

What are non ferrous metals?

A

Consist of elements such as copper and aluminum or alloys such as brass.

108
Q

Aluminum is obtained from an ore called what?

A

Bauxite. Aluminum is light weight weighing about 1/3 the weight of steel. To avoid fracturing, aluminum should be bent using a bend radius of 3x the material thickness.

109
Q

Gauging aluminum.

A

It is gauged in decimal parts of an inch or the Brown and Sharpe gauge or American standard wire gauge. Anodized aluminum thickens and strengthens.

110
Q

Describe copper.

A

It is a reddish brown metal that is considered an element. Highly malleable and ductile. Excellant conductor of heat and electricity. When copper oxides it forms a greenish coating called patina. Long lasting. Copper is gauged by weight in ounces per square foot.

111
Q

Brass is the common name used for all copper zinc alloys.

A

True. Brasses are highly malleable and are easily cast, forged, rolled and pressed.

112
Q

What is thermosetting?

A

Thermosetting plastics harden under heat. Thermoplastic materials soften when heated and solidify when cooled.

113
Q

What is fibrous glass duct?

A

It is made from silica (sand) which is one of the most abundant materials on earth. It is heated until it melts into a molten liquid state and then spun into thin glass fibers.

114
Q

Ferrous metals or metals with iron are gauged how?

A

By using the US standard gauge.

115
Q

What is mild steel also known as?

A

Low carbon steel.

116
Q

What is a standing seam?

A

They are 3w with a flange and a pocket.

117
Q

What is an end slip joint?

A

S shaped joint. 3w

118
Q

What is another name for a single seam?

A

Penned seam. Standing L shape with horizontal bend connecting. 3w

119
Q

What is a double seam?

A

It is a single seam that is hammered over to form the double seam. 3w

120
Q

What is a flanged edge?

A

It gives a project or a fitting a means to attach it to something else as well as strengthening the edge

121
Q

What is acme lock?

A

Is used as a means of joining the longitudinal edges of lighter gauge pipe.

122
Q

Explain proprietary connections.

A

Nexus and ductmate are designed to replace angle iron flanges on medium and higher pressure ductwork and larger lower pressure ductwork.

123
Q

What is the difference between a full v notch and a v notch?

A

A full v notch has an included 90° angle and a v notch does not have a 90° angle.

124
Q

What are fasteners?

A

These are mechanical devices designed to hold, join, assemble or secure various components of an object or structure.

125
Q

What is another name for blind rivets?

A

Pop rivets and are named so because they can be set from one side of the work.

126
Q

What are two basic types of blind rivets?

A

Open ended and closed end. With a closed end the rivet itself is sealed to prevent the entry of vapors or liquids.

127
Q

Three head styles of rivets?

A

Dome head
Countersunk rivets
Large flange rivets

128
Q

The total thickness of the material being joined by a blind rivet is referred to as grip range.

A

True. Rivet burrs are like washers.

129
Q

One length of rivet will fasten several different thicknesses of material.

A

True.

130
Q

Ordering a rivet?

A 
A- Rivet material
S- mandrel material
4- rivet diameter measured in 32nds
2- maximum grip measured in 16ths
D- rivet head style
131
Q

Self piercing sheet metal screws have a sharp point.

A

True. Self drilling screws though have a drill bit end also called TEK screws.

132
Q

Describe silicone.

A

It is a long lasting caulking that remains flexible after curing. It usually cannot be painted.

133
Q

What is latex caulking?

A

Easy to work with and to clean up. Can be easily smoothed and paint adheres well to it.

134
Q

Describe butyl caulking.

A

It is a rubber based material that performs well in sealing between dissimilar materials. Very water resistance and should be used outside.

135
Q

When should metal nosing be used?

A

When the air exceeds 4000 feet per minute.

136
Q

What are two types of burns in welding?

A

Surface or minor burns 1st degree burns

Major burns 2nd or 3rd degree burns

137
Q

Light rays from welding are dangerous for a distance of up to 50’ even when reflected.

A

True.

138
Q

Radiant energy has three categories. What are they?

A

Visible light
Ultraviolet rays
Infra-red rays

139
Q

What are visible light rays?

A

Visible light rays are those you can see. They may come from the source or they may be reflected off shiny surfaces.

140
Q

What are ultraviolet rays?

A

These are invisible. They cause burns to exposed skin and blistering of the eyeballs and is more common with electric arc welding.

141
Q

What is an arc flash?

A

Sometimes called welding flash or arc eye is the term commonly used to describe eyes burned by ultraviolet rays.

142
Q

What are infrared rays?

A

These are also invisible. They penetrate deeply and can cause temperature increases and burns to the exposed skin. These Ray’s may also penetrate the interior of the eye and can cause damage.

143
Q

Over a long period of time, infrared rays can cause cataracts.

A

True.

144
Q

Gases created during welding, such as ozone, carbon monoxide iron nitrogen dioxide are extremely toxic.

A

True. These gases can be fatal.

145
Q

What are gases that cause cancer called?

A

Carcinogens

146
Q

Explain metal fume fever.

A

Sometimes known as zinc chills produces flu-like symptoms from inhaling fumes if certain metal oxides.

147
Q

Metals that produce fumes.

A

Aluminum- irritation of respiratory system.
Chromium- lung cancer, some forms are carcinogens.
Iron- irritation of nose and lungs, usually non-permanent
Lead- toxic vapour affect nervous and digestive systems and kidneys. Can be fatal.
Zinc- irritation of respiratory system. Zinc chills

148
Q

Welding gases and gasses produced by welding

A

Argon, helium and carbon dioxide- these gases are non-toxic but inhaling concentrated amounts can lead to suffocation.
Ozone- low concentrations cause headaches and irritation of the nose and throat.

149
Q

What is natural general ventilation for welding purposes?

A

An unlimited fresh air supply.

150
Q

What is mechanical general ventilation in welding?

A

Air is pumped into the shop, passes through and is vented outdoors through ductwork, doors and windows.

151
Q

What is local ventilation in welding?

A

Exhaust fans capture fumes at their source and exhausts them outdoors. Also known as source extraction.

152
Q

What are three ways to render containers safe for welding and cutting?

A

Boiling in a caustic solution
Inert gases purging
Steaming

153
Q

Oxygen, argon, nitrogen and helium are filled to 2200 psi to 2500 psi.

A

True.

154
Q

Rules for handling cylinders.

A

Store in a cool, dry, well ventilated room
Store oxygen and acetylene cylinders separately (min. 20’ apart)
Store and use cylinders vertically
Valve protection caps should be not be removed until cylinder is secure

155
Q

Welding lenses will protect your eyes from 99% of the harmful Ray’s emitted during the welding process.

A

True.

156
Q

What is a shade 10 welding helmet?

A

Most common is low to medium amperage.

157
Q

An accumulation of hot slag or excessive heat on concrete floors can cause the concrete surface to explode.

A

True. The best clothing materials for welding and cutting are leather, wool and denim because they repel slag.

158
Q

Avoid wearing synthetics because they have a tendency to melt.

A

Welders leather gauntlet style gloves provide the best protection.

159
Q

How should you protect others at the workplace while welding?

A

Position blinds, screens and/or shields to protect other personnel and equipment from direct contact with flying sparks and light rays.

160
Q

Oxygen is a colorless, tasteless gas and is the element in the air that supports life and combustion.

A

True.

161
Q

Do oxygen and oil mix well?

A

No they don’t. Oxygen and oil equals explosion or fire.

162
Q

The oxygen cylinder is a high pressure vessel and must be treated with care.

A

True. Oxygen cylinders are a hot drawn product. This means that the cylinder is formed from a single piece of steel and hot worked to shape. There is no girth or longitudinal seams.

163
Q

How do you thread oxygen cylinders?

A

All oxygen cylinders are right hand thread.

164
Q

What is an oxygen cylinder valve safety device?

A

A metal rupture disc protects the oxygen cylinder from extreme pressure rise caused by heat or fire.

165
Q

What is acetylene?

A

C2h2 is a hydrocarbon compound. Acetylene gas is colorless, but has a strong and irritating odor. Acetylene has a critical point of 193 kPa (28psi) pressure at 21°C.

166
Q

Acetylene is not safe when compressed beyond 103 kPa (15 psi)

A

True.

167
Q

Explain acetylene cylinders.

A

They are of welded construction. This is because they operate at a much lower working pressures and therefore, their design and construction does not need to be at the same standards as oxygen cylinders.

168
Q

Acetylene gas is dissolved in a chemically similar liquid called what?

A

Acetone. This is a colorless, flammable, quite volatile liquid with a strong odor. It makes acetylene cylinders safe at high pressures.

169
Q

What are fusible metal plugs?

A

It is a main safety feature on acetylene cylinders. It melts out in case of fire, thus allowing a controlled escape of gas.

170
Q

What are regulators used for in acetylene cylinders?

A

To reduce the source pressure to a working or operating pressure.
To maintain a constant delivery pressure and gas volume regardless of pressure changes at the source.

171
Q

What are reverse flow check valves in acetylene torches?

A

Also known as check valves are used to prevent the reverse flow of gases through the torch, hoses or regulators.

172
Q

What is another name for spot welding?

A

Resistance welding. Uncoated materials, such as black iron, are easily spot welded, as well as coated materials like galvanized iron.

173
Q

What is a reasonable tip diameter for spot welding?

A

1/8” plus 2 metal thicknesses of the metal being used.

174
Q

What is shieldedmetal arc welding?

A

SMAW is also known as stick welding and the electrode is sometimes called a rod. The electrode has a metal core wire and it is covered with flux coating.

175
Q

What is gas metal arc welding?

A

GMAW , commonly referred to as MIG welding. It is an arc welding process that joins metals by heating them with an electric arc established between a continuously fed filler metal electrode and the workpiece.

176
Q

What is flux core arc welding?

A

FCAW uses an arc established between a continuously fed consumable flux cored wire electrode and the workpiece.

177
Q

What is gas tungsten arc welding?

A

GTAW also called tungsten inert gas (TIG), is a process in which fusion welding is accomplished by the heat of an electric arc drawn between a non-consumable tungsten electrode and the work.

178
Q

Do not light torches using a mixture of oxygen and acetylene.

A

True.

179
Q

What is the first step in shutting down a welding torch?

A

Close the oxygen cylinder valve.

180
Q

What happens when an acetylene torch backfires?

A

The flame backs up into the tip

181
Q

What happens with a burn back on acetylene torches?

A

Combustion takes place steadily in the tip and mixer of the torch.

182
Q

Explain flashbacks in acetylene torches.

A

It is when one gas that backs up into the other line, this forming an explosive mixture and resulting in an explosion or series of explosions known as flashbacks.

183
Q

Explain brazing.

A

Also called braze welding requires very close tolerances. Dissimilar metals may be joined using brazing. Joints up to 60,000 psi tensile strength are possible.

184
Q

Brazing filler metals are mainly copper/zinc based alloys also called brass.

A

True.

185
Q

What are fluxes?

A

Fluxes are deoxidation agents also known as cleansing agents.

186
Q

Iron and steels oxidize slowly in moist air to form the oxide known as rust.

A

True. When steels are heated to kindling temperature (red hot) and a jet of oxygen is directed onto the hot spot, rapid oxidation occurs.

187
Q

What materials are suitable for cutting with a torch?

A

Ferrous metals, such as steel, are good to cut but non-ferrous metals, such as copper do not cut well.

188
Q

What are the advantages of plasma arc cutting?

A

Greater speed
No preheating is required
It has a very narrow heat affect zone
Any metal that conducts electricity can be cut

189
Q

What are abrasive cutting disks?

A

Also known as zip disks, are often attached to angle grinders and can be used with very little equipment.

1st Year Sheet Metal (5 decks)

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