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Bolts, Nuts, and Washers

20 questions

All types20Multiple choice11Matching4Ordering5
Question 1Question →

A technician is replacing hardware on a heavy-duty truck trailer hitch assembly that specifies high-tensile SAE Grade 8 bolts. When sorting through hex-head fasteners in the shop inventory, which bolt head marking correctly identifies an SAE Grade 8 fastener?

Show answer & explanation

Answer: Six radial slash marks evenly spaced around the head

Answer

Six radial slash marks evenly spaced around the head
For standard SAE inch-series steel bolts, the tensile strength grade is determined by counting the radial slash marks stamped on the bolt head and adding 2 (Grade=radial lines+2\text{Grade} = \text{radial lines} + 2). An SAE Grade 8 bolt has 6 radial lines (6+2=86 + 2 = 8), indicating a minimum tensile strength of approximately 150,000 psi.

Step-by-Step Solution

1
Recall the SAE bolt head grading formula for standard inch-series hex-head bolts.
The formula is SAE Grade=Number of Radial Lines+2\text{SAE Grade} = \text{Number of Radial Lines} + 2.
SAE standard J429 defines tensile strength categories by radial tick marks on the bolt head starting with Grade 5 (3 lines) and Grade 8 (6 lines).
2
Calculate the required number of radial lines for an SAE Grade 8 bolt.
Radial Lines=8−2=6\text{Radial Lines} = 8 - 2 = 6.
An SAE Grade 8 bolt requires 6 radial slash marks stamped into the top of the hex head.

Key Concept

SAE Hex Bolt Grade Identification via Radial Lines
Estimated Time:45s
Question 2Question →

When assembling mechanical components subjected to varying temperatures, dynamic stress, and vibration, technicians must select specialized hardware to secure bolted joints. Match each specialized nut or washer to its primary operational function.

Click a left item, then click its matching right item

Items

Belleville (conical disc) washer
Castle (castellated) nut
Nylon-insert lock nut
Star (toothed) lock washer

Matches

Show answer & explanation

Answer

Belleville washer matches with maintaining constant clamping force and absorbing thermal movement; Castle nut matches with providing a positive mechanical lock with a cotter pin; Nylon-insert lock nut matches with using an integrated polymer collar for prevailing torque; Star lock washer matches with employing serrated teeth that bite into mating surfaces.
Each fastener and washer is designed for a distinct engineering purpose: the Belleville washer provides spring tension to compensate for thermal changes and dynamic loading; the castellated nut provides a fail-safe positive mechanical stop via a cotter pin; the nylon-insert lock nut maintains position through friction from a deformed polymer insert; and the star washer bites into metal faces to resist twisting and establish good electrical grounding.

Step-by-Step Solution

1
Identify the primary spring characteristic of the Belleville washer
Matched to maintaining clamping load under thermal expansion cycles
Its conical disc design acts as a high-rate spring specifically suited for thermal growth and heavy loading.
2
Identify the retention method of a castellated nut
Matched to positive mechanical locking with a cotter pin
The crown slots receive a cotter pin through a drilled hole, providing positive locking independent of thread friction.
3
Identify the prevailing torque mechanism of a nylon-insert lock nut
Matched to polymer collar deformation against bolt threads
The unthreaded nylon ring undergoes elastic deformation when tightened, generating frictional resistance.
4
Identify the surface engagement of a toothed star washer
Matched to serrated teeth biting into mating surfaces
The multiple angled teeth bite into both the fastener underside and workpiece surface to resist back-out.

Key Concept

Operating principles and retention mechanisms of specialized nuts and locking washers
Estimated Time:1m 15s
Question 3Question →

While replacing a suspension control arm on an imported vehicle, a technician inspects a steel hex-head bolt stamped with the number 10.910.9 on the top of the head. What do these stamped numbers indicate about the fastener?

Show answer & explanation

Answer: The bolt is a metric fastener belonging to Property Class 10.9, indicating high tensile strength.

Answer

The stamped marking indicates that the bolt is a metric fastener belonging to Property Class 10.9, denoting a high tensile strength.
On automotive and industrial fasteners, decimal numerical stamps (such as 8.88.8, 10.910.9, and 12.912.9) identify ISO metric property classes. A marking of 10.910.9 indicates a quenched and tempered medium carbon alloy steel bolt with high tensile strength (nominal tensile strength of 1040 MPa1{}040\text{ MPa}), commonly used in high-stress chassis and suspension applications.

Step-by-Step Solution

1
Analyze the stamping format on the hex bolt head.
The marking is a two-digit decimal number (10.910.9).
Metric fasteners use embossed decimal numbers to represent mechanical property classes, whereas SAE fractional fasteners use radial lines.
2
Interpret the meaning of the metric Property Class designation.
Property Class 10.910.9 specifies a minimum tensile strength of approximately 1000 MPa1{}000\text{ MPa} and a yield strength that is 90%90\% of the tensile strength (900 MPa900\text{ MPa}).
The first number multiplied by 100100 gives nominal tensile strength in megapascals, and the decimal indicates the ratio of yield strength to tensile strength.

Key Concept

Metric Fastener Property Class Identification
Estimated Time:45s
Question 4Question →

In automotive maintenance and mechanical fabrication, selecting the correct washer is critical for maintaining joint integrity, managing stress, and preventing fastener failure. Match each washer type on the left with its primary mechanical function on the right.

Click a left item, then click its matching right item

Items

Flat Washer (Plain SAE/USS)
Split-Ring Lock Washer
Belleville (Conical Disc) Washer
Tooth (Star) Lock Washer

Matches

Show answer & explanation

Answer

Flat Washer matches with distributing clamping force over a broader surface area; Split-Ring Lock Washer matches with providing spring tension via helical offset ends to deter loosening; Belleville Washer matches with maintaining continuous clamping preload under thermal expansion; Tooth Lock Washer matches with employing serrated teeth that cut into surfaces for vibration resistance and electrical grounding.
Each washer is designed for a distinct mechanical purpose: Flat washers spread clamping pressure over a wider footprint to protect workpieces. Split-ring lock washers supply basic spring tension and minor frictional bite against moderate vibration. Belleville washers function as high-rate conical springs to maintain preload during thermal cycling and severe shock. Tooth (star) lock washers utilize multiple sharp serrations to grip metal surfaces firmly and penetrate protective coatings for chassis grounding.

Step-by-Step Solution

1
Identify the primary function of a standard flat washer.
Flat washers act as smooth load distributors to prevent surface indentation and galling.
They have no inherent locking mechanism and serve to increase contact surface area.
2
Differentiate between mechanical locking washers based on physical features.
The split-ring washer utilizes helical spring compression, while the tooth/star washer uses biting teeth that penetrate coatings.
Split-ring washers provide tension through their split helical shape, whereas star washers provide mechanical bite and grounding.
3
Determine the application of a conical disc (Belleville) washer.
Belleville washers act as high-capacity disc springs.
Their cupped conical profile accommodates dimensional changes caused by heat and heavy dynamic loads.

Key Concept

Engineering roles, load distribution mechanics, and locking principles of standard, helical, conical, and serrated washers.
Estimated Time:1m 0s
Question 5Question →

An automotive mechanic is selecting hardware to secure a replacement engine mount bracket and requires fasteners with an SAE Grade 5 rating. Which markings on the top of a steel bolt head designate an SAE Grade 5 bolt?

Show answer & explanation

Answer: Three radial lines stamped on the bolt head

Answer

Three radial lines stamped on the bolt head
Under the SAE standard bolt grading system, the tensile strength grade of a standard hex bolt is calculated by adding 2 to the number of radial lines stamped on the head. Therefore, a bolt with three radial lines represents an SAE Grade 5 fastener (3+2=53 + 2 = 5), which is medium-strength carbon steel commonly used in automotive applications.

Step-by-Step Solution

1
Recall the SAE bolt head marking formula for tensile strength grading.
The rule states: SAE Grade=Number of Radial Lines+2\text{SAE Grade} = \text{Number of Radial Lines} + 2.
SAE (Society of Automotive Engineers) standardizes steel bolt tensile ratings using radial slash marks on the top of the hex head.
2
Determine the number of radial lines required for an SAE Grade 5 bolt.
Radial Lines=5−2=3\text{Radial Lines} = 5 - 2 = 3.
Subtracting 2 from the target grade of 5 yields 3 radial lines.

Key Concept

SAE Bolt Grade Identification by Radial Head Markings
Estimated Time:1m 0s
Question 6Question →

A shop technician is organizing carbon steel hex-head fasteners by their load-bearing capacity before restocking service bins. Arrange the following SAE bolt head markings in order from lowest minimum tensile strength to highest minimum tensile strength.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

Plain/unmarked head (Grade 2), followed by 3 radial lines (Grade 5), then 5 radial lines (Grade 7), and finally 6 radial lines (Grade 8).
SAE bolt strength is identified by counting the radial lines on the hex head and adding 2. An unmarked bolt head is SAE Grade 2 (~74,000 psi), 3 radial lines designate SAE Grade 5 (~120,000 psi), 5 radial lines designate SAE Grade 7 (~133,000 psi), and 6 radial lines designate SAE Grade 8 (~150,000 psi). Arranging them from lowest to highest tensile capacity yields: unmarked bolt, 3 radial lines, 5 radial lines, and 6 radial lines.

Step-by-Step Solution

1
Identify the standard rule for determining SAE bolt grades from head markings.
The SAE grade equals the number of radial hash marks plus 2 (Grade = Lines + 2). An unmarked head represents SAE Grade 2.
SAE standard J429 defines fastener tensile strength categories by the count of radial lines embossed on the bolt head.
2
Calculate the SAE grade and corresponding minimum tensile strength for each fastener marking.
Unmarked = Grade 2 (74000 psi74{}000\text{ psi}); 3 lines = Grade 5 (120000 psi120{}000\text{ psi}); 5 lines = Grade 7 (133000 psi133{}000\text{ psi}); 6 lines = Grade 8 (150000 psi150{}000\text{ psi}).
Fastener strength increases sequentially with higher grade numbers.
3
Arrange the fasteners in ascending order from lowest tensile strength to highest tensile strength.
Item with no radial lines → Item with 3 radial lines → Item with 5 radial lines → Item with 6 radial lines.
This orders the bolts from lowest load capacity (74000 psi74{}000\text{ psi}) to highest load capacity (150000 psi150{}000\text{ psi}).

Key Concept

SAE Bolt Grade Identification and Tensile Strength Hierarchy
Estimated Time:1m 0s
Question 7Question →

A mechanic is reviewing a technical parts manual to replace damaged hardware on a heavy equipment mounting plate. The specification calls for a 3/8-16 UNC×1-1/2 in3/8\text{-}16\text{ UNC} \times 1\text{-}1/2\text{ in} hex cap screw. In this standardized Unified National fastener callout, what does the number 1616 represent?

Show answer & explanation

Answer: The number of threads per inch along the bolt shank

Answer

The number of threads per inch along the bolt shank
In standard imperial fastener nomenclature (Unified Thread Standard), the number immediately following the nominal diameter indicates the thread pitch, defined as the number of threads per inch (TPI). In 3/8-16 UNC×1-1/2 in3/8\text{-}16\text{ UNC} \times 1\text{-}1/2\text{ in}, 1616 specifies that there are 1616 complete thread crests per inch along the shank.

Step-by-Step Solution

1
Analyze the standard SAE Unified National thread callout format
The standard nomenclature is formatted as: [Nominal Diameter] - [Threads Per Inch] [Thread Series] x [Fastener Length].
Deconstructing the callout reveals the distinct mechanical property defined by each segment.
2
Map each value from 3/8-16 UNC×1-1/2 in3/8\text{-}16\text{ UNC} \times 1\text{-}1/2\text{ in} to its corresponding dimension
3/8 in3/8\text{ in} is the nominal major diameter, 1616 is the thread pitch (threads per inch), UNC\text{UNC} indicates Unified National Coarse, and 1-1/2 in1\text{-}1/2\text{ in} is the overall length measured from under the bolt head.
The second parameter in imperial fractional fastener callouts always specifies the thread density per linear inch.

Key Concept

Standard Unified National (SAE) fastener callout nomenclature
Estimated Time:1m 0s
Question 8Question →

A mechanic removes a damaged hex bolt marked with exactly six radial lines on its head. The service manual specifies that a metric replacement of equivalent tensile strength can be used, provided it is secured with a castle nut and cotter pin. Which of the following correctly identifies the SAE grade of the original bolt, its equivalent metric property class, and the mechanical purpose of the specified nut combination?

Show answer & explanation

Answer: SAE Grade 8; Metric Class 10.9; provides a positive mechanical lock that prevents the nut from backing off under high vibration.

Answer

SAE Grade 8; Metric Class 10.9; provides a positive mechanical lock that prevents the nut from backing off under high vibration.
The correct combination accurately calculates the SAE grade by adding two to the six radial lines, correctly matches Grade 8 to its exact Metric Class 10.9 equivalent based on tensile strength, and correctly identifies that a castle nut paired with a cotter pin creates a physical barrier to prevent rotational loosening under severe vibration.

Step-by-Step Solution

1
Calculate the SAE bolt grade based on the head markings.
6 radial lines + 2 = SAE Grade 8.
The standard rule for identifying SAE fractional bolts is to add 2 to the number of radial lines on the bolt head to determine its grade.
2
Determine the equivalent metric property class for SAE Grade 8.
Metric Class 10.9.
An SAE Grade 8 bolt has a tensile strength of 150,000 psi. The closest equivalent in the metric system is Property Class 10.9, which has a tensile strength of 1040 MPa (approximately 150,800 psi).
3
Identify the mechanical function of a castle nut and cotter pin.
Provides a positive mechanical lock against vibration.
Unlike friction-based lock washers or spring-tension washers, a cotter pin passing through a drilled bolt shaft and the slots of a castle nut creates a physical barrier that makes it impossible for the nut to rotate, which is critical in high-vibration assemblies like steering linkages.

Key Concept

Fastener Grade Identification, Metric Equivalency, and Specialized Nuts
Question 9Question →

An automotive technician is rebuilding a heavy-duty suspension assembly subject to extreme cyclic shock and severe thermal variations. The technical specification requires replacing an unmarked standard low-carbon steel bolt with a fastener capable of handling a minimum tensile strength of 150,000 psi, paired with a positive mechanical locking device that physically prevents the nut from backing off even if clamping preload is lost. Which bolt head marking and locking fastener combination correctly meets these requirements?

Show answer & explanation

Answer: A bolt head with 6 radial lines, paired with a castellated nut, a drilled bolt shank, and a steel cotter pin

Answer

A bolt head with 6 radial lines, paired with a castellated nut, a drilled bolt shank, and a steel cotter pin
The combination featuring 6 radial lines on the bolt head paired with a castellated nut, a drilled shank, and a cotter pin satisfies all engineering constraints. The 6 radial lines represent an SAE Grade 8 medium carbon alloy steel fastener with a minimum tensile strength of 150,000 psi. The castellated nut with a steel cotter pin provides positive mechanical locking, meaning rotation is physically blocked regardless of thermal degradation or clamping load loss.

Step-by-Step Solution

1
Determine the required SAE bolt grade for a 150,000 psi tensile strength requirement.
SAE Grade 8 provides a minimum tensile strength of 150,000 psi (compared to Grade 5 at 120,000 psi and Grade 2 at 74,000 psi).
High-stress structural and suspension applications require high-strength alloy steel fasteners.
2
Calculate the radial line marking on the hex bolt head.
Six radial lines on the bolt head denote an SAE Grade 8 bolt (formula: number of radial lines + 2 = SAE Grade).
SAE grade markings use radial lines extending outward from the center of the bolt head.
3
Select the locking mechanism providing positive mechanical retention.
A castellated (or slotted) nut secured with a cotter pin through a drilled shank physically locks the nut to the bolt.
Friction-based locking methods (nylon inserts, split washers, serrated tooth washers) can fail under severe vibration, dynamic shock, or extreme temperatures, whereas a pinned castle nut provides fail-safe positive retention.

Key Concept

Fastener tensile strength ratings (SAE bolt grades) and positive mechanical locking methods
Estimated Time:1m 30s
Question 10Question →

During the inspection of replacement hardware for an industrial engine mount, a technician examines a hex cap screw embossed with the metric property class designation 10.9 on its head. What do the numbers in this metric property class designation specifically indicate about the bolt's mechanical strength?

Show answer & explanation

Answer: A nominal tensile strength of 1000 MPa1000\text{ MPa} with a minimum yield strength of 900 MPa900\text{ MPa}

Answer

A nominal tensile strength of 1000 MPa1000\text{ MPa} with a minimum yield strength of 900 MPa900\text{ MPa}
The metric property class system uses a two-part decimal number (such as 8.8, 10.9, or 12.9) stamped on the bolt head. The number before the decimal point represents 1/1001/100 of the minimum ultimate tensile strength in megapascals (10×100=1000 MPa10 \times 100 = 1000\text{ MPa}). The number after the decimal point indicates the yield strength ratio as a decimal multiplier (0.90.9), meaning the bolt begins yielding at 90%90\% of its ultimate tensile strength (0.9×1000=900 MPa0.9 \times 1000 = 900\text{ MPa}).

Step-by-Step Solution

1
Interpret the whole number preceding the decimal point in the property class designation (10).
Multiplying 10 by 100 MPa100\text{ MPa} yields a nominal ultimate tensile strength of 1000 MPa1000\text{ MPa}.
In the metric fastener grading standard (ISO 898-1), the number before the decimal represents 1/1001/100 of the nominal tensile strength in megapascals.
2
Interpret the decimal value following the point (.9).
Multiplying the tensile strength (1000 MPa1000\text{ MPa}) by 0.9 yields a minimum yield strength of 900 MPa900\text{ MPa}.
The number after the decimal indicates the ratio of yield strength (or proof stress) to nominal tensile strength (90%90\% or 0.9).
3
Synthesize the two mechanical values to identify the complete property definition.
The bolt has an ultimate tensile strength of 1000 MPa1000\text{ MPa} and a minimum yield strength of 900 MPa900\text{ MPa}.
Both values are required to define the mechanical class of the fastener under tensile loading.

Key Concept

Metric bolt property class decimal designations define tensile strength (X×100 MPaX \times 100\text{ MPa}) and yield strength ratio (0.Y×tensile strength0.Y \times \text{tensile strength}).
Estimated Time:1m 30s
Question 11Question →

A mechanic is securing a heavy steel mounting bracket to a vehicle frame rail using a standard vibration-resistant through-bolt fastener assembly. Arrange the components in the correct physical sequence along the fastener axis, starting at the bolt head insertion side and proceeding to the threaded end. In what sequence must these components be assembled from the bolt head to the securing nut?

Drag items to arrange them in the correct order

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Answer

Hex head cap bolt → Plain flat washer (head side) → Mating structural steel plates (bracket and frame rail) → Helical split-ring lock washer (nut side) → Finished hex nut
In a standard through-bolted mechanical assembly, the load path begins at the bolt head, passes through a flat washer that distributes clamping pressure, penetrates the joined workpieces, engages a split-ring helical lock washer on the nut side to maintain continuous spring preload against vibration, and terminates at the hex nut which applies the tightening torque.

Step-by-Step Solution

1
Identify the head-side fastener components and primary load distributor.
Position the plain flat washer over the shank directly against the bearing surface of the hex head cap bolt.
Flat washers distribute axial preload over a broader surface area and prevent the rotating bolt head from galling the workpiece surface during tightening.
2
Pass the bolt shank through the clearance holes of the mating components.
Align and sandwich the bracket flange and structural frame rail over the bolt shank.
The structural joint members must be centered within the grip length of the through-bolt.
3
Install the vibration-retention device and securing fastener onto the protruding threaded shank.
Slide the helical split-ring lock washer onto the bolt shank against the inner workpiece face, followed by the finished hex nut.
The lock washer must seat directly beneath the turned nut so its deflected spring edges bite into the nut bearing face to resist rotational loosening under cyclic mechanical vibration.

Key Concept

Proper mechanical through-bolt joint stackup and washer positioning
Estimated Time:1m 15s
Question 12Question →

While assembling a bracket on a vehicle chassis, a mechanic selects a standard hex cap screw that has 3 distinct radial lines stamped onto the top of its head. According to SAE standards, what is the strength grade of this bolt?

Show answer & explanation

Answer: Grade 5

Answer

Grade 5
On SAE standard hex head bolts, tensile strength is indicated by radial lines on the head. Adding 2 to the number of radial lines gives the SAE grade. For 3 radial lines, 3+2=53 + 2 = 5, indicating an SAE Grade 5 bolt.

Step-by-Step Solution

1
Count the number of radial slash marks on the hex bolt head.
The bolt head displays 3 radial lines.
SAE (Society of Automotive Engineers) markings use radial lines extending from the center of the bolt head to indicate tensile strength.
2
Apply the standard SAE bolt grade conversion rule: Grade=Number of Radial Lines+2\text{Grade} = \text{Number of Radial Lines} + 2.
3+2=53 + 2 = 5, identifying the fastener as an SAE Grade 5 bolt.
An SAE Grade 2 bolt has no radial marks, so 2 must always be added to the count of radial lines.

Key Concept

SAE Bolt Grade Identification by Radial Lines
Estimated Time:45s
Question 13Question →

Match each type of fastener or washer hardware with its primary mechanical function.

Click a left item, then click its matching right item

Items

Castle nut
Flat washer
Split-lock washer
Wing nut

Matches

Show answer & explanation

Answer

Castle nut matches with using slotted cutouts aligned with a cotter pin for positive mechanical locking; Flat washer matches with distributing clamping load over a larger surface area; Split-lock washer matches with providing continuous spring tension to resist loosening under vibration; Wing nut matches with featuring two large side tabs for quick assembly by hand.
Each hardware item serves a distinct role: a castle nut pairs with a cotter pin for positive locking; a flat washer distributes compressive loads to prevent joint deformation; a split-lock washer provides spring force against vibration; and a wing nut enables toolless adjustment by hand.

Step-by-Step Solution

1
Examine the mechanical design features of each fastener component.
Castle nuts use cotter pins, flat washers provide broad surface contact, split-lock washers supply helical spring tension, and wing nuts feature extended tabs for grip.
Fasteners and washers are engineered with distinct physical features tailored to specific mechanical roles.
2
Pair each hardware term with its corresponding functional definition.
All four components are matched with their standard operational functions.
Matching structural traits to their practical applications confirms correct hardware selection.

Key Concept

Functions and mechanical characteristics of specialized nuts and washers in mechanical assemblies
Estimated Time:45s
Question 14Question →

To determine the SAE grade rating of a standard hex head steel bolt, what calculation is applied to the number of radial slash lines stamped on the bolt head?

Show answer & explanation

Answer: Add 2 to the number of radial lines

Answer

Add 2 to the number of radial lines
Under SAE (Society of Automotive Engineers) specifications, the strength grade of a steel hex bolt is determined by counting the radial slash marks on the bolt head and adding 2. For instance, a bolt with zero lines is Grade 2, a bolt with 3 lines is Grade 5, and a bolt with 6 lines is Grade 8.

Step-by-Step Solution

1
Recall the SAE J429 standard for identifying bolt tensile strength grades from head markings.
Recognize that radial slash lines radiating from the center of an SAE hex head indicate tensile strength.
Standardized markings allow mechanics to verify fastener load capabilities quickly.
2
Apply the standard formula: SAE Grade=Number of Radial Lines+2\text{SAE Grade} = \text{Number of Radial Lines} + 2.
Adding 2 to the line count yields the correct SAE grade (0 lines = Grade 2, 3 lines = Grade 5, 6 lines = Grade 8).
The baseline standard grade (Grade 2) has zero markings, establishing the offset of 2.

Key Concept

SAE Bolt Grade Identification Rule
Estimated Time:30s
Question 15Question →

A technician is organizing standard steel fasteners by their load-bearing capacity. Arrange the following SAE hex cap bolts in order of their tensile strength, from lowest strength to highest strength.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

From lowest to highest tensile strength: Bolt with no radial lines (SAE Grade 2), Bolt with 3 radial lines (SAE Grade 5), Bolt with 5 radial lines (SAE Grade 7), and Bolt with 6 radial lines (SAE Grade 8).
SAE steel bolt strength is designated by radial lines stamped on the bolt head. The formula to find the grade is the number of radial lines plus 2. A plain bolt head with no lines designates SAE Grade 2 (~74,000 psi minimum tensile strength). A bolt head with 3 radial lines indicates SAE Grade 5 (3 + 2 = 5, ~120,000 psi). A bolt head with 5 radial lines indicates SAE Grade 7 (5 + 2 = 7, ~133,000 psi). A bolt head with 6 radial lines indicates SAE Grade 8 (6 + 2 = 8, ~150,000 psi). Therefore, the correct order from weakest to strongest is Grade 2 (no lines), Grade 5 (3 lines), Grade 7 (5 lines), and Grade 8 (6 lines).

Step-by-Step Solution

1
Identify the standard rule for determining SAE bolt grades from radial head markings.
The SAE grade equals the number of radial slash lines stamped on the bolt head plus 2 (Grade=radial lines+2\text{Grade} = \text{radial lines} + 2). A head with no markings corresponds to Grade 2.
Understanding head marking standards is essential for determining fastener strength and load capacity.
2
Calculate the grade and relative tensile strength for each fastener.
No lines = Grade 2 (~74,000 psi); 3 lines = Grade 5 (120,000 psi); 5 lines = Grade 7 (133,000 psi); 6 lines = Grade 8 (150,000 psi).
Tensile strength increases directly with higher SAE grade numbers.
3
Sequence the fasteners from lowest tensile strength to highest tensile strength.
Order: Grade 2 (no lines) < Grade 5 (3 lines) < Grade 7 (5 lines) < Grade 8 (6 lines).
Proper sequencing ensures hardware meets structural and mechanical requirements without risking joint failure.

Key Concept

SAE Bolt Grade Identification and Relative Tensile Strength
Estimated Time:45s
Question 16Question →

A technician is selecting replacement hardware for an equipment bracket and inspects a box of standard Unified National coarse (UNC) hex bolts marked with the specification 3/8-16 x 1-1/2. What does the number 16 indicate in this standard fastener callout?

Show answer & explanation

Answer: Number of threads per inch along the bolt shank

Answer

The number 16 indicates the number of threads per inch (TPI) along the bolt shank.
In standard Unified National fastener designations, the number immediately following the nominal diameter indicates the thread pitch, defined as the number of threads per inch (TPI). A 3/8-16 bolt has 16 complete thread ridges per linear inch of threaded shank.

Step-by-Step Solution

1
Break down the standard Unified National fastener notation format: Major Diameter - Threads Per Inch x Length.
In the callout 3/8-16 x 1-1/2, '3/8' is the nominal bolt diameter in inches, '16' is the thread density, and '1-1/2' is the length under the head in inches.
Standard SAE fastener specifications always present dimensions in the sequence of diameter, thread pitch (threads per inch), and overall length.

Key Concept

Standard Unified National (SAE) bolt dimension and thread nomenclature.
Estimated Time:45s
Question 17Question →

In mechanical assembly and automotive repair, distinct fasteners and washers are engineered for specific retention, locking, and load-distribution tasks. Match each fastener component to its primary functional design characteristic.

Click a left item, then click its matching right item

Items

Nylon-insert lock nut
Wing nut
Flat washer
Castle nut

Matches

Show answer & explanation

Answer

Nylon-insert lock nut matches with using an internal synthetic ring to grip threads; Wing nut matches with dual lateral flanges for tool-free manual tightening; Flat washer matches with spreading clamping force across a larger surface area; Castle nut matches with incorporating upper slots to accommodate a cotter pin.
Each fastener fulfills a distinct mechanical requirement: the nylon-insert lock nut prevents vibration-induced loosening via thread friction; the wing nut enables tool-free manual operation; the flat washer distributes bearing load; and the castle nut creates a positive mechanical interlock with a drilled bolt and cotter pin.

Step-by-Step Solution

1
Identify the frictional locking mechanism of the nylon-insert nut.
Matched with the synthetic ring that creates thread interference.
The nylon insert resists backing off under rotational vibration without damaging threads.
2
Identify the ergonomic shape and operation of the wing nut.
Matched with the lateral flanges designed for hand tightening.
Wing nuts are intended for light-duty, frequently disassembled joints where wrench access is unnecessary.
3
Identify the foundational load-bearing purpose of a plain flat washer.
Matched with distributing clamp force and preventing surface damage.
Flat washers increase the contact footprint beneath the fastener head or nut.
4
Identify the positive locking configuration of a slotted castle nut.
Matched with slots that align with a cotter pin in a drilled bolt.
Castle nuts provide a fail-safe mechanical retention method for critical safety assemblies like wheel bearings and steering linkages.

Key Concept

Mechanical functions and operational design differences among standard shop nuts and washers
Question 18Question →

A mechanic is securing a suspension component using a threaded stud, a castellated nut, and a cotter pin. Place the following installation and locking steps in the correct chronological sequence from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: (1) Thread and torque the castellated nut to the initial specification, (2) Inspect the alignment between the nut slots and the stud hole, (3) Tighten slightly further to align the nearest slot if needed, and (4) Insert the cotter pin and bend the prongs to lock the fastener.
Proper installation of a castellated nut requires seating the joint to base torque first, checking hole-to-slot alignment, advancing the nut only in the tightening direction to achieve alignment, and finally installing and spreading the cotter pin prongs to positively lock the assembly.

Step-by-Step Solution

1
Torque the castellated nut to the lower end of the specified torque range.
The joint is properly seated under clamping force.
Fasteners must achieve sufficient clamping load before locking devices are installed.
2
Inspect the position of the nut slots relative to the drilled hole in the bolt or stud.
Determine if direct alignment exists or if further rotation is required.
A cotter pin cannot pass through unless a slot and the hole form an unobstructed passageway.
3
Rotate the nut clockwise slightly to bring the nearest slot into alignment with the hole.
The slot aligns with the hole while maintaining or slightly increasing proper torque.
Shop safety rules dictate that castellated nuts should never be loosened to align cotter pin holes, as loosening compromises joint preload.
4
Insert the cotter pin completely through the assembly and bend one prong over the end of the stud and the other around the side of the nut.
The nut is positively locked against rotational movement.
Positive mechanical locking prevents fastener loosening caused by vibration and dynamic operational loads.

Key Concept

Proper installation procedure and positive mechanical locking of castellated nuts using cotter pins.
Estimated Time:1m 0s
Question 19Question →

An automotive technician installing an alternator mounting bracket consults the service manual, which specifies an M10×1.5×40\text{M}10 \times 1.5 \times 40 hex cap screw. What does the value 1.51.5 represent in this standard metric fastener callout?

Show answer & explanation

Answer: The distance in millimeters between adjacent thread crests

Answer

The value 1.5 represents the thread pitch, defined as the distance in millimeters between adjacent thread crests.
In standard metric fastener notation (M10 x 1.5 x 40), the letter 'M' indicates metric ISO thread profile, the first number (10) represents the nominal major diameter in millimeters, the second number (1.5) represents the thread pitch in millimeters between adjacent crests, and the final number (40) is the length of the bolt in millimeters.

Step-by-Step Solution

1
Deconstruct the metric fastener callout notation M10 x 1.5 x 40 into its standard components.
'M' indicates metric ISO thread; '10' is nominal major diameter in millimeters; '1.5' is thread pitch; '40' is fastener shank length in millimeters.
Metric fastener specifications follow the standard format: Metric Designation + Major Diameter (mm) x Thread Pitch (mm) x Length (mm).
2
Determine the physical definition of thread pitch in metric fastener standards.
A thread pitch of 1.5 specifies that there is a 1.5 mm linear distance from the peak of one thread to the peak of the adjacent thread.
Unlike Imperial threads that count threads per inch (TPI), metric fasteners directly measure the axial distance between individual crests.

Key Concept

Metric fastener callout structure and thread pitch specification
Estimated Time:1m 0s
Question 20Question →

A mechanic is securing two steel plates together using a through-bolt, two flat washers, a split-ring lock washer, and a standard hex nut. In what sequential order should these hardware components and materials be assembled from the bolt head side to the nut side?

Drag items to arrange them in the correct order

Show answer & explanation

Answer

First flat washer under bolt head, passed through the joined plates, followed by the second flat washer, the split-ring lock washer, and finally the hex nut.
In standard mechanical assembly, a through-bolted joint follows a specific hardware order: the bolt head holds a flat washer to distribute pressure; the bolt passes through the workpiece; the opposite side receives a second flat washer for load distribution, followed by the split-ring lock washer to maintain tension, and finishes with the hex nut.

Step-by-Step Solution

1
Place the initial flat washer onto the bolt shank up to the bolt head.
Protects the front workpiece surface and distributes clamping force under the head.
Prevents head embedment into the material during tightening.
2
Insert the bolt assembly through the workpiece clearance holes.
Hardware spans the joint plates.
Aligns and joins the two structural components.
3
Slide the second flat washer over the threaded end against the workpiece.
Provides a smooth, wide bearing surface on the nut side.
Prevents the lock washer from digging into the softer workpiece material.
4
Slide the split-ring lock washer over the threads against the flat washer.
Prepares spring-tension retention.
Maintains constant tension against the nut to resist vibrational loosening.
5
Thread and torque the hex nut onto the bolt shank.
Compresses the lock washer and clamps the joint.
Develops the required clamping force across the entire fastener stack.

Key Concept

Through-bolt fastener assembly stack-up sequence and washer placement rules
Estimated Time:1m 0s
Bolts, Nuts, and Washers Practice Questions — Armed Services Vocational Aptitude Battery (ASVAB) | Examkin