Fasteners MCQ Quiz - Objective Question with Answer for Fasteners - Download Free PDF

Explanation:-

Hexagonal socket head cap screw :

• Socket Head Cap Screw is the standard for all of the high-strength hex recess-driven screws.

• Hexagonal Recess is used primarily on socket products.
• The points on the hex bit produce a high-pressure point against the contact location of the hex recess during assembly.
• Torque transfer from the bit to the screw is excellent. Driver bits have excessive wear.
• Typical applications are high-end instrumentation, and medical and test equipment.

Explanation:

Lead:

• Lead is the distance a threaded component moves along the matching component during one complete revolution.
• For a single start thread, the lead is equal to the pitch.

Single-start thread:

• A single-start thread has one continuous thread running along the body of the screw. They are usually cheap and commonly used.
• For a single start thread, the lead is equal to the pitch

Multi-start thread:

• A multi-start thread consists of two or more intertwined running parallel to one another.
• The lead distance of a double start thread is twice that of the single start thread, and a triple start thread has thrice that of the single start thread.

​For triple start thread:

Lead = 3 × Pitch

• Multi-start threads maintain a shallow thread depth relative to their longer lead distance. Another design advantage of a multi-start thread is that more contact surface is engaged in a single thread rotation.

Additional Information 

Flank:

• The surface joining the crest and the root is known as the flank

Pitch:

• It is the distance from a point on one thread to the corresponding point on the adjacent thread measured parallel to the axis

Explanation:

Acme thread:

• This thread is a modification of the square thread.
• It has an included angle of 29°.
• It is preferred for many jobs because it is fairly easy to machine.
• Acme threads are used in lathe lead screws.
• This form of thread enables the easy engagement of the half nut.
• The metric acme thread has an included angle of 30°.

Different types of threads and included angle:

Explanation:

Washers 

• Washers are used to distribute the clamping pressure over a larger area and prevent the surface damaged (marking).
• They also provide an increased bearing surface for bolt heads and nuts.
• Washers are manufactured in light, medium, heavy, and extra heavy series.
• Washers are of two main types:
  • Plain washers are inserted under screw heads or nuts to provide a suitable bearing area while tightening and to protect the component from damage.
  • Lock washers are used to prevent loosening due to vibrations, movements, or temperature variations. Common types include:
    • Spring washer
    • Snakeproof washer
    • Crinkle washer
    • Tab washer

Spring lock washer

• A spring washer, also known as a locking washer or split washer, is specifically designed to prevent the loosening of nuts and bolts due to vibration. It is a type of washer with a split or helical shape, which provides a spring-like action when compressed.

• When a nut is tightened onto a bolt with a spring washer placed between them, the spring washer creates tension and applies a continuous force against the nut. This force helps to maintain the tightness of the connection, even when subjected to vibration or external forces.

• As the nut tightens the washer against the piece below, one edge of the washer is caused to dig itself into that piece.
• It results in increasing the resistance so that the nut will not loosen so easily which means it holds a nut at place.

Lock washers

• A lock washer is used to prevent a bolt or nut from loosening under vibration.
• The split ring lock washer is being rapidly replaced by lock washers designed for a specific application.

Tooth type lock washers

• These washers have teeth that bite deep into both the screw head and work surface.
• Their design is such that they actually lock lighter as vibrations increase.
• They are classified into two types.
  • External type: Should be used where possible as it provides the greatest resistance.
  • Internal type: Used with small head screws and where it is desirable to hide the teeth either for appearance or to prevent snagging.

Explanation:

• The purpose of leveling bolts is to adjust the height of a machine or equipment.
• Leveling bolts are used to ensure that the machine is properly aligned and leveled on a flat surface.
• By adjusting the height of the leveling bolts, the machine can be raised or lowered to achieve the desired level position.
• This is important for the proper functioning, stability, and alignment of the machine.
• Leveling bolts help in compensating for any unevenness or irregularities in the surface on which the machine is placed.

Explanation:

Nut

A nut is a type of fastener with a threaded hole.

There are the following types of nut used.

Dome nut		The dome nut is similar to the hexagonal nut with a spherical cap at the top. It is also known as Acorn Nuts or Cap nuts. The dome nut is used to protect the end of the bolt from corrosion.
Capstan Nut		This is in the form of a cylinder with holes drilled in the curved surface. These holes can be used to turn the nut by placing a Tommy bar in it.
Wing Nut		The wing nut is used to tightening two mating parts by hand and is used for light-duty purposes. When the mating parts are frequently used to adjust (such as tightening of hacksaw blade), this nut is used.
Lock nut		The thin lock nut is first tightened down with ordinary force, and then the upper nut (thicker nut) down upon it. The upper nut is then held tightly while the lower nut is slackened back against it.

Explanation:

• Nuts are used along with bolts in an assembly which may loosen due to vibration.
• Different types of nut-locking devices are used depending on the severity of the condition in which the fastener is used.
• The following are the most commonly used types:
  • Swan nut
  • Groove nut
  • Castle nut
  • Lock nut
• The dimensions of a bolt head or a nut cannot be expressed exactly in terms of the nominal diameter of the bolt.
• However, for engineering drawing purposes, the dimensions are approximated in terms of the diameter "d".

The height of the standard hexagonal nut is 0.8 d. The threads of the bolt in the standard nut will not fail by shear. So, the height of the nut is the most important design dimension.

Explanation:

A thread is a ridge of a uniform cross-section which follows the path of a helix around the cylinder or cone, either externally or internally.

The different standards of V threads for a screw thread are:

Explanation:

Basically, when a helical groove is cut or generated over a cylindrical or conical section, threads are formed. 

Fasteners: A mechanical fastener is a device that is used to mechanically join (or fasten) two or more objects together.

Some Fasteners are:

• Pins
• Rivets
• Nails
• Concrete Anchors

Threaded Fasteners: The fasteners in which threads are designed on either the outer or inner surfaces.

Some threaded Fasteners are:

• Bolts: They are basically threaded fasteners normally used with nuts. 
• Screws: They engage either with a preformed or self-made internal thread. 
• Stud: A metal rod or shaft with threads on both sides is called a stud.

Important Points

The nails come under fasteners but not under threaded Fasteners.

Explanation:

 Foundation Bolt

• For some machines, it is very essential to hold down the machines firmly on the foundation to prevent them from moving.
• For this purpose, various types of foundation bolts or anchor bolts are used.
• There are basically four types of Foundation Bolts.

Concept:

Pitch:

• The distance from one point on a thread to the same point on the adjacent thread.
• The reciprocal of the pitch is the number of threads per inch.

Thread:

• Formed on the screw in a helix.
• Helix is the path of a point traveling around an imaginary cylindrical such that its axial and circumferential velocities maintain a constant ratio.
• When a single helix is making a screw, it is called a single start thread.
• In a single start thread, the lead and pitch are the same.

• In the case of two start threads, one thread is wound within the other exactly in the middle. This enables the lead of the helix to increase without increasing the pitch.

• Lead = Pitch × Number of the starts

Explanation:

The distance from a point on a thread to the corresponding point on the next thread of a screw is called pitch.

Additional Information Flute:

• It is made in the form of an open cylindrical air column about 66 cm long.
• Its fundamental pitch is middle C (C4) and it has a range of about three octaves to C7.
• Sound is produced from a flute by blowing onto a sharp edge, causing air enclosed in a tube to vibrate.

Explanation:

Foundation Bolt

• For some machines, it is very essential to hold down the machines firmly on the foundation to prevent them from moving.
• For this purpose, various types of foundation bolts or anchor bolts are used.
• There are basically four types of Foundation Bolts.

Explanation:

• Nuts are used along with bolts in an assembly which may loosen due to vibration.
• Different types of nut-locking devices are used depending on the severity of the condition in which the fastener is used.
• The following are the most commonly used types:

Swan nut (Wiles nut)

• A slot is cut halfway across the nut.
• A screw is fitted with a clearance hole on the top part and matching thread on the lower part of the nut.

Penn, ring or grooved nut:

• It has an upper portion hexagonal and a lower part cylindrical.
• It is largely used where the bolt passes through connected pieces.
• The bottom portion is cylindrical and is recessed to receive the tip of the locking set screw.
• The bolt hole requires counterboring to receive the cylindrical portion of the nut.
• In order to prevent bruising of the latter bu the case-hardened tip of the set screw, it is recessed.

Slotted/Castle nut:

• It consists of a hexagonal portion with a cylindrical upper part which is a slotted inline with the center of each face.
• The split pin passes through two slots in the nut and a hole in the bolt so that a positive lock is obtained unless the pin shears.
• It is extensively used on jobs subjected to sudden shocks and considerable vibrations.

Explanation:

Pitch (p): It is the distance from the center of one rivet to the center of the next rivet measured parallel to the seam.

Back pitch (p_b): It is the perpendicular distance between the center lines of the successive rows.

Diagonal pitch (p_d): It is the distance between the centers of the rivets in adjacent rows of zig-zag riveted joint.

Explanation:

Stud:

• A metal rod or shaft with threads on both sides is called a stud.
• A metal rod or shaft with threads throughout the rod is called a Fully threaded stud. 
• Studs are used with assemblies which are to be separated frequently.
• They are externally threaded headless fasteners.
• One end usually meets a tapped component and the other with a standard nut. 
• The three types of Fully threaded stud bolts are A, B, C