PG.456-562-brngs,Metals,Heat

What type of bearings are commonly shown in cross-section diagrams of horizontal shaft assemblies supported at both ends?

Ball bearings.

In a typical bearing housing that uses rings to splash oil onto the rotating shaft and bearings, what are those rings called?

Oil rings.

A bearing assembly drawing shows a large housing with oil rings visible at the bottom and breathers visible at the top. What type of lubrication system is in use, and what are the oil rings used for?

This is an oil bath / oil ring lubrication system. The oil rings pick up oil from the reservoir at the bottom of the housing as the shaft rotates and distribute it to the bearing surfaces.

In a typical bearing housing that uses rings to splash oil onto the rotating shaft and bearings , what components are added to the top of the housing to allow air to enter and exit so internal pressure can equalize?

Breathers

What is the main purpose of the oil rings in a splash-lubricated bearing assembly?

To distribute lubricant (oil) to the bearings as the shaft rotates.

What is the main purpose of breathers in a splash-lubricated bearing assembly?

To allow air to enter/exit the housing to equalize pressure and prevent vacuum or pressure buildup.

In standard industrial shaft assemblies using ball bearings, what arrangement is typically used to handle thermal expansion of the shaft?

A combination of fixed and floating bearing arrangements.

A shaft assembly uses two sets of tapered roller bearings — one set on the left end and one set on the right end — with both sets mounted so that the wide ends of the tapered rollers face outward (away from center). Is this arrangement correct bearing theory?

False (they are ball bearings).No. This is incorrect bearing theory. Tapered roller bearings must be mounted in opposed pairs so that axial (thrust) loads are properly handled. When both sets face the same direction without opposition, the assembly cannot control axial movement correctly.

A shaft-and-housing assembly shows bearings with rollers that are shaped like a truncated cone. The rollers run between a tapered inner race and a tapered outer race (cup and cone). What type of bearings are these, and what kind of loads can they handle?

Tapered roller bearings. They can handle both radial loads and axial (thrust) loads simultaneously.

An assembly drawing shows a shaft supported at both ends by pairs of rollers. The rollers are cylindrical in shape and mounted in open housings. What type of bearings are these?

Cylindrical roller bearings

An assembly shows a shaft supported by bearings contained in pillow-block style housings bolted to a frame. The bearing element visible inside appears to be a spherical outer ring surrounding a ball or roller inner element. What type of bearing arrangement does this represent?

Self-aligning or spherical bearings in plummer/pillow block housings, which allow for shaft misalignment.

A motor assembly cross-section shows the shaft supported on one end by a single large ball bearing and on the other end by two smaller ball bearings. What is the purpose of having two bearings on one end versus one on the other?

The end with two bearings is the drive (loaded) end, providing greater radial and axial load capacity. The single bearing end is typically the free/float end, allowing for thermal expansion of the shaft.

A cross-section shows a bearing housing with two rows of balls visible on each side of the shaft. The balls on one side are set at an opposing angle to the balls on the other side. Is this correct bearing theory for handling both radial and axial loads?

Yes. Opposing angular contact ball bearings (back-to-back or face-to-face arrangement) correctly handle both radial loads and bidirectional axial (thrust) loads.

What does the term metallurgy refer to in industrial materials training?

Deriving metals from natural ores and recycled scrap, then forming them into useful shapes for industry.

Metals are divided into two main categories based on whether they contain iron. What are those two categories?

Ferrous (contain iron) and non-ferrous (do not contain iron).

Name the four metals or alloy groups that are the focus of basic industrial metallurgy training.

1. Cast iron (ferrous);

2. Steel and its alloys (ferrous);

3. Aluminum and its alloys (non-ferrous);

4. Copper and its alloys (non-ferrous).

What is the typical carbon content range for cast iron?

3.0% to 6.5%.

What are the four main types of cast iron taught in industrial materials training?

Gray cast iron

white cast iron

malleable cast iron

nodular cast iron.

What are the key characteristics of gray cast iron?

Good wear qualities but brittle and not malleable due to hardness.

What are the key characteristics of white cast iron?

Hard and brittle; good compressive strength and resistant to wear/abrasion.

What are the key characteristics of malleable cast iron?

Much stronger than gray or white cast iron; can be hammered, rolled, and bent without breaking.

What are the key characteristics of nodular cast iron?

Easy to cast and machine; good wear characteristics.

Steels are classified into three categories based on carbon content. What are the categories and their carbon ranges?

Low carbon (0.05%–0.20%), medium carbon (0.20%–0.50%), high carbon (0.50%–2.00%).

A chart shows steel and cast iron plotted against carbon content (% carbon). Steel occupies the range from approximately 0.05% to 1.7% carbon, while cast iron occupies the range from approximately 3.0% to 6.67% carbon. What does this chart tell you about the relationship between carbon content and the classification of the metal?

Carbon content determines whether the material is classified as steel or cast iron. Steel contains less than 1.7% carbon, while cast iron contains between 3% and 6.67% carbon. Higher carbon content in steel increases hardness but decreases weldability and forgeability.

List six qualities that are considered when selecting a particular steel for an industrial application.

Hardenability

formability

weldability

machinability

availability

processing costs.

In the SAE steel numbering system, what do the first digit, second digit, and last two digits represent?

First digit = type of main material

second digit = quantity of main material

last two digits = carbon concentration to 0.01%.

What does the SAE designation 51100 indicate about a steel?

Chromium steel alloy containing 1% chromium and 1.00% carbon.

What are the three categories of steel based on carbon content, what are their carbon percentage ranges, and what is a common name for each?

Low Carbon Steel: 0.05% to 0.20% carbon — also called Mild Steel

Medium Carbon Steel: 0.20% to 0.50% carbon — also called Machinery Steel

High Carbon Steel: 0.50% to 2.00% carbon — also called Tool Steel

What are the two primary methods used to produce steel, and how does each method work?

Blast Furnace (Basic Oxygen Furnace): Uses coke, iron ore, and limestone to produce pig iron, which is then converted to steel. Limestone removes impurities from the iron ore.

Electric Arc Furnace (EAF): Uses an electrical current to melt scrap steel and iron to produce molten steel. EAFs now account for over 70% of steel production in the United State

What is coke, how is it made, and why is it used in steelmaking?

Coke is a porous, hard black rock of concentrated carbon. It is made by crushing coal into powder, charging it into an oven, and heating it in the absence of oxygen. This removes volatile matter such as oil, tar, hydrogen, nitrogen, and sulfur. Coke is used as a fuel and carbon source in the blast furnace to produce pig iron.

What does the SAE designation 1060 indicate about a steel?

Plain-carbon steel containing 0.60% carbon.

What is the main difference between the SAE and AISI steel classification systems?

AISI adds a prefix that identifies the manufacturing process.

In the AISI classification system, what does each of the following prefix letters indicate?

C

E

B

C = Open-hearth process (standard steel)

E = Electric arc furnace process (alloyed steel)

B = Bessemer process (acid carbon steel)

Using the SAE steel numbering system, decode the following designation: SAE 1060

SAE 1060 is a plain-carbon steel (1xxx = carbon steel), with no significant alloying element quantity beyond the base (10 = plain carbon), and containing 0.60% carbon (last two digits = 60, divided by 100).

What is the main characteristic of stainless steel, and what element provides that property?

Resistance to corrosion, provided by chromium (11.5%–27% chromium content).

In the AFNOR steel classification system, what does the designation XC 38 indicate?

XC steel with 0.38% carbon content.

Using the AFNOR classification system, decode the following steel designation: 35 NCD 16

35 = 0.35% carbon content (divide by 100)

N = Nickel alloying element

C = Chromium alloying element

D = Molybdenum alloying element

16 = 4% Nickel (divide by 4, since Nickel uses the ÷4 rule)

In the AFNOR steel classification system, what does the designation 35 NCD 16 indicate?

Slightly alloyed heat-treatable high-quality steel containing 0.35% carbon, nickel, chromium, and molybdenum (4% total alloying elements).

Using the AFNOR classification system, decode the following steel designation: Z6 CN 18 09

Z = Heavily alloyed steel (Z Steel)

6 = 0.06% carbon (divide by 100)

C = Chromium

N = Nickel

18 = 18% Chromium (read directly for Z steel)

09 = 9% Nickel (drop the leading zero, read as 9%)

Since chromium exceeds 11%, this is classified as Stainless Steel.

What ASTM designation is typically used for standard American structural steels such as angles, beams, and channels?

ASTM A36

How is a standard steel angle dimensioned on an industrial drawing? Give the format and an example.

Symbol + long leg × short leg × thickness × length (example: 3 × 2 × 3/16 × 6’-0” or 2 × 2 × 3/16 even if the legs are equal).

Using the SAE steel numbering system, decode the following designation: SAE 1060

SAE 1060 is a plain-carbon steel (1xxx = carbon steel), with no significant alloying element quantity beyond the base (10 = plain carbon), and containing 0.60% carbon (last two digits = 60, divided by 100).

Using the SAE steel numbering system, decode the following designation: SAE 51100

SAE 51100 is a chromium steel alloy (5xxx = chromium steels), containing 1% chromium (first digit after type = 1), and 1.00% carbon (last two digits = 100, meaning 1.00%).

What is the objective of heat treatment, and what properties can be changed through heat treatment?

The objective of heat treating is to improve the mechanical properties and/or remove the internal stresses of an alloy by heating and then cooling it. Properties that can be changed include: hardness, wear resistance, tensile strength, elasticity, and toughness. Heat treatment modifies the structure of an alloy without changing its chemical composition.

Describe what happens during each of the following heat treatment processes and what effect each has on the metal:

a) Hardening

b) Tempering

c) Annealing

d) Normalizing

a) Hardening: The part is heated to a given temperature then quenched (rapidly cooled). Increases: elastic limit, resistance to rupture, hardness. Decreases: stretching percent, resilience. Only steels with 0.30%–0.80% carbon can be successfully hardened under normal conditions.

b) Tempering: Performed after hardening; reheats the part to a temperature lower than the hardening temperature, then cools it. Reduces brittleness while maintaining most of the hardness gained and releases internal stress. Slightly decreases: elastic limit, resistance to rupture, hardness. Slightly increases: stretching percent, resilience.

c) Annealing: Heats the part above the upper transformation zone, then cools it slowly inside the furnace. Significantly increases: stretching percent, resilience. Significantly decreases: elastic limit.

d) Normalizing: Heats material slightly above its upper critical temperature then allows it to cool in room-temperature air (faster cooling than annealing). Increases: ductility. Decreases: hardness.

What are the three main methods of hardness measurement used in the mechanical industry, and what are their abbreviations?

Rockwell — abbreviated HRb or HRc

Vickers — abbreviated HV

Brinell — abbreviated HB

What is the difference between First Angle Projection (European) and Third Angle Projection (American/US), and how can you tell which system a drawing uses?

In Third Angle (American) Projection, the view is placed on the same side as the observer — the top view is above the front view, and the right side view is to the right of the front view. In First Angle (European) Projection, the view is placed on the opposite side from the observer — the top view is below the front view, and the right side view is to the left of the front view. Each system has a standardized projection symbol shown on the drawing (a truncated cone viewed from different ends) to identify which system is used.

What is orthographic (orthogonal) viewing, and why is it used in mechanical drawings instead of perspective viewing?

Orthographic viewing means viewing an object perpendicularly (at right angles) to each of its surfaces. It is used in mechanical drawings because perspective viewing distorts lengths and shapes — a rectangular table looks like a parallelogram from a corner angle. Orthographic viewing shows the true shape and size of each surface, which is essential for accurately describing and manufacturing parts.

When is it necessary to use three views (front, top, and side) rather than just two views to fully describe a part?

Three views are needed when two views leave ambiguity about the shape of the part. For example, a front view and right side view may correctly show all dimensions but could correspond to several different shapes (straight cut, angled cut, curved cut in the corner). Adding the top (plan) view removes any doubt and fully defines the part's shape. The rule is: always use the minimum number of views with the least number of hidden lines that fully describe the part.

Describe the following line types from a mechanical drawing and state the function of each:

a) Continuous thick line (0.7 mm)

b) Short broken medium line (0.35 mm)

c) Mixed thin line (0.18 mm)

d) Mixed thin line with heavy ends and corners

a) Continuous Thick Line: Represents visible edges of the object.

b) Short Broken Medium Line: Represents hidden edges (features not visible in that view).

c) Mixed Thin Line (centerline): Used for axes of symmetry, hole centers, position references, and pitch circle diameters.

d) Mixed Thin with Heavy Ends and Corners: Cutting plane lines — shows where a theoretical cut is made for a sectional view.

What is the rule regarding dimension lines and extension lines crossing each other?4

Extension lines may cross object lines or other extension lines. However, dimension lines must NOT cross any other line. Dimension lines should be solid from one end to the other and not broken. A dimension line is never a continuation of an object line. Dimension lines should not be placed inside the view of an object.

How are dimensions read on a drawing, and where are the dimension numbers placed relative to the dimension line?

Dimensions are always read from the bottom or the right-hand edge of the drawing. Dimension numbers are located 1 mm from the dimension line and are centered on it. Numbers for linear dimensions should be drawn above the dimension line, parallel to it. At least 6 mm of space should exist between the object line and the first dimension line.

How is a 45° chamfer dimensioned on a drawing? Give at least two acceptable methods.

A 45° chamfer can be dimensioned using any of these methods:

Stating the length followed by the angle: e.g., 5 × 45°

Stating both legs: e.g., 5 × 5

Showing the length with the 45° angle noted separately

A chamfer that is NOT at 45° must be dimensioned with one length and one angle.

What symbol is placed before a dimension number to indicate a diameter, and what letter is used to indicate a radius? Why is it important to distinguish between them?

The symbol Ø (phi) is placed before a number to indicate diameter. The letter R is used to indicate a radius. It is important to distinguish them because a diameter is twice the radius — confusing them when making a part would result in the wrong size. On drawings where confusion is possible, both symbols must be used clearly.

What is a sectional view, and why is it used in mechanical drawings?

A sectional view represents the part of an object that remains after a portion is assumed to have been cut away and removed along a cutting plane. It is used to show internal details of a component without relying on hidden (dashed) lines. When a component has complex internal features — such as bores, counterbores, or internal passages — hidden lines alone can be confusing. A sectional view eliminates this confusion by showing the interior as a visible, cross-hatched surface.

What is a cutting plane line, what does it look like, and what do the arrows on it indicate?

A cutting plane line shows where the theoretical cut is made to produce a sectional view. It is drawn as a mixed thin line with heavy ends and corners (0.18 mm thin dashes with 0.7 mm heavy ends). The arrows on the cutting plane line point in the direction from which the sectional view is observed. If more than one section is shown on the same drawing, different letters (A-A, B-B, etc.) must be used to identify each cutting plane and its corresponding section view.

What are cross-hatch (section) lines, at what angles are they typically drawn, and what do they represent?

Cross-hatch lines are uniformly spaced thin lines used to represent the theoretically cut surface in a sectional view — showing the solid material that was cut through. They are normally drawn at 30°, 45°, or 60° to the horizontal reference plane of the drawing, with 45° recommended for most detail drawings. Spacing increases as the drawing size increases; clarity should dictate the spacing used.

List the key rules from the Dimension Guidelines that every person reading or creating a mechanical drawing should follo

Don't use any dimension more than once on a drawing.

Place each dimension in the view that most clearly shows the feature being dimensioned.

Use the minimum number of dimensions needed to accurately describe the part. If a dimension can be calculated from existing dimensions, do not include it.

Make extension lines touch the object.

Do not cross dimension lines with any other line.

Do not dimension directly to object lines; use extension lines instead.

Always show center lines at the point from which an arc or radius is drawn.

Dimension lines for linear dimensions must be parallel to the surface being dimensioned.

Radii are dimensioned with an arrow from the center point to the surface. Diameters are dimensioned with an arrow pointing toward the center, touching the outside of the diameter.

Dimension angles and sloped surfaces with one angle and one linear dimension.

What is the miter line technique in view projection, and how is it used to transfer depth measurements between views?

The miter line is a 45° diagonal line used to transfer depth dimensions between the top view and the side view (or vice versa) in orthographic projection. To use it: horizontal lines from the top view are projected to the miter line, then turned 90° downward (or across) into the side view at the correct depth. This technique ensures that depth measurements are consistent between the top and side views without measuring each dimension separately, maintaining accuracy in third-angle or first-angle projection layouts.