• SkillCat Team

Fasteners

Updated: Jun 17

Key Hand Tools: Chapter 1


Nails & Screws


In this module, we will cover:

- What a fastener is,

- What a nail is, and

- What a screw is Skip to quiz!


Nail


A fastener joins two or more objects together. For example, a fastener could attach two pieces of plywood. In this module, we will cover two types of fasteners:

  • Nails, and

  • Screws

A nail is a type of fastener with three parts:

  • A flat head,

  • A smooth shaft, and

  • A point

You can see an example of a nail in the picture to the right.


Nails are driven through two objects to connect them. The picture to the right shows an exploded view of two pieces of plywood held together by four nails. Note that the nail goes through the two objects it is fastening together.


The point is the sharp end of the nail. The point goes into the material you are fastening. The head of the nail is flat and wide. It is opposite of the point. The shaft connects the point and the head of the nail. The shaft is made of smooth metal.


The shaft of a nail is smooth, so there is less friction between the nail and the material. The smooth shaft allows nails to be easily inserted and pulled out of the material.

You should use a nail when you need to prevent objects from sliding past each other. You should not use nails when two objects are being pulled apart. Nails also bend under heavy loads instead of snapping like other fasteners.


For example, you use nails when attaching siding to a house. Gravity is pulling downward on the siding. The downward force makes the siding want to slide down the framing. The nail will prevent the siding from sliding down the wall frame.


You should not use nails in wet environments. The moisture can cause the material to expand and contract. When the material expands and contracts, the nail loosens.


Screws


A screw is a type of fastener with three parts:

  • A head,

  • A threaded shaft, and

  • A point

Just like a nail, screws hold together two objects. You can see an example of a screw in the picture to the right.


Just like a nail, a screw has a sharp point. The point goes in the material you are screwing into.


A screw also has a head with grooves in the metal. Tools grip the grooves in the screw head. For example, a screwdriver will insert into the grooves of the screw head. The grooves make it easier to twist the screw into the material.


A threaded shaft connects the point and head of a screw. A thread is a metal ridge around the shaft of the screw.


The threading increases the surface area of the screw. With more surface area, there is more friction between the screw and the material. The friction makes it challenging to pull out a screw.


You can understand the effects of threading and friction by rubbing two rough objects together. Since both objects are rough, it can be challenging for them to slide past each other. If both objects are smooth, like your fingers, you can easily slide your fingers past each other.


Screws are great for fastening two objects together that need a close connection. The threading of a screw draws the materials closer together. Threads also make it more difficult for components to be pulled apart.


Screws are better at resisting pulling forces than nails. Nails are better at resisting sliding forces than screws.


Nails are also more ductile than screws. A ductile material will bend before breaking. The ductile material of nails makes them excellent for bearing weight. If you place a significant load on a screw, the screw will snap.


In this module, you learned that nails have a smooth shaft that resists sliding forces. Screws have a threaded shaft that resists pulling forces.



Types of Screws


In this module, we will cover:

- Types of screws,

-Types of screw heads, and

- When to use each type of screw Skip to quiz!


Types of Screws

Recall that a screw is a metal fastener with a threaded shaft. There are many types of screws. In this module, we will cover

  • Wood screws,

  • Sheet metal screws, and

  • Self-tapping screws

We will go into detail on each type of screw in the following sections.


Wood Screws

Wood screws are a type of screw designed to be used on softer materials like wood and plastic. Like a regular screw, a wood screw has a point, threaded shaft, and a grooved head. Like all screws, wood screws are excellent at resisting pulling forces.


The threaded shaft of a wood screw has more space between each thread. More space between threads helps the screw easily enter the wood.


Sheet Metal Screws


A sheet metal screw has a sharp pointed end, a threaded shaft, and a rounded head known as a pan head. A pan head allows the screw to create an airtight seal between two thin sheets of metal, called sheet metal.

There is less space between threads on a sheet metal screw. When threads are closer together, we call it fine threading. The fine threading allows the screw to easily create a hole in sheet metal.


Sheet metal screws are used to connect two thin metal objects, called sheet metal. The screw’s pan head creates an airtight seal around the hole. Like all screws, sheet metal screws can resist tremendous amounts of pulling forces.


For example, ductwork is created by combining pieces of sheet metal. The connection must be airtight. Since the connection must be air air-tight, sheet metal screws can be used to combine pieces of ductwork. The pan head prevents any air from leaking.


Self-Tapping Screws


As you insert a screw into the material, the screw creates tracks in the hole. The tracks are called tapping. The threading and tapping block the screw from being pulled straight out. Threading and tapping are the reason screws can resist pulling forces.

Self-tapping screws have a point, threaded shaft, and a round head. Self-tapping screws create tapping as they rotate into the material. Before using a self-tapping screw, you must create a small hole in the material.


Self-tapping screws are mainly used on metal. Self-tapping screws can also be used on wood or plastic. Self-tapping screws save you time by tapping the hole as you insert the screw. Without a self-tapping screw, you would have to create the tapping with a separate tool.


Like all screws, self-tapping screws excel at resisting pulling forces. Self-tapping screws are standard on gutters and sheet metal roofing.


Screw Heads


Recall that a screw head is a metal groove in the top of a screw. Tools attach into screw heads when you are inserting or removing screws from the material.


Some common types of screw heads are:

  • Slotted,

  • Crosshead,

  • Torx,

  • Allen head, and

  • Hex head


A slotted screw has a single-line groove in the head. It looks like a “minus” sign. Slotted screws have fewer contact points for tools to grip. A tool with fewer contact points is more likely to slip out of the head.


A crosshead screw has two line grooves in the screw head. The grooves look like a “plus” sign. Crosshead screws are also known as a phillips screw. Crosshead screws have four points of contact. The four points of contact allow tools to grip the screw head firmly.


The head of a torx screw has a star groove. The six points of contact provide even more grip between the tool and screw head. Torx heads are great when a tool needs to put a large amount of rotational force on a screw.


Allen head screws have a hexagon-shaped groove in the screw head. Like a torx screw, allen head screws provide excellent grip between the tool and the head of the screw.


A hex-head screw has a hexagonal-shaped head. Unlike most screw heads, there are no grooves cut into hex head screws. Instead of grooves, tools grip the outer edges of the screw head.


In this module, you learned about:

  • Types of screws,

  • Types of screw heads, and

  • When to use each type of screw



Bolts


This module will cover:

- What a bolt is,

- How to use a bolt, and

- Types of bolts Skip to quiz!


What is a Bolt?


Recall that a fastener fixes two or more objects together. A bolt is a cylindrical piece of threaded metal that is used as a fastener. Bolts can handle much higher loads than a nail or screw. Bolts are commonly used in heavy machinery for this reason.


The bolt is made up of two parts:

  • The head, and

  • The shaft


The head of the bolt is similar to the head of a screw or nail. When you want to tighten or loosen a bolt, you will use tools to grip the head of the bolt. Note that a bolt head does not have grooves like a screw head.


Recall that threading helps fasteners resist pulling forces. The shaft of a bolt is threaded. The shaft of a bolt usually does not have a sharp point like a screw or nail. Bolts are not drilled into materials. Instead, bolts are screwed into pre-made tapped holes.


Bolts are typically used to hold objects together that will experience high loads. Bolts can be easily removed to take apart any objects we put together. Bolts can be used in small objects like toys and large objects like heavy machinery.


Types of Threading


Bolts can have variations in their threading. Some common types of threading are:

  • Fully threaded,

  • Partially threaded,

  • Coarse threading, and

  • Fine threading


All bolts can have two types of threading on the shaft:

  • Threaded, and

  • Partially threaded

Threaded bolts have threading from the head of the bolt to the tip. Partially threaded bolts have threading on part of the shaft, but not the entire shaft.


There are also two types of threading spacing:

  • Coarse threading, and

  • Fine threading

The types of threading refer to the distance between each thread on the bolt shaft.


Coarse threads have more distance between each thread on the shaft. Fine threads have less distance between each thread on the shaft. You can see a comparison in the image to the right.


Types of Bolts


There are many different types of bolts like:

  • Hex bolts,

  • Hex tap bolts,

  • Lag bolts, and

  • Carriage bolts


A hex bolt is a partially threaded bolt with a six-sided head. Hex bolts are the most common bolt you will find. Hex bolts are used on bridges, buildings, and automobiles.

Recall, a hex bolt is a partially threaded bolt. A hex tap bolt has the same six sided head as a hex bolt, but the shaft is fully threaded. Since hex tap bolts are fully threaded, they can be used in many situations.


Recall, a wood screw is a threaded screw designed for wood and plastic. A lag bolt is a large wood screw with a six sided head. Lag bolts can handle heavier loads than standard wood screws.


Recall, a self tapping fasteners taps the hole as you insert it. A lag bolt is self tapping. Lag bolts are often used to connect heavy lumber or other materials that experience a heavy load.


A carriage bolt has a round head and flat tip. Carriage bolts are fully threaded along the shaft. Carriage bolts are commonly used to attach wood to metal. They can also be used for attaching two pieces of wood.


A threaded rod, sometimes called a stud, is a metal shaft with threads going down the entire length of the rod. A threaded rod is similar to a bolt, but a threaded rod does not have a head. Threaded rods are used as a pin for connecting two objects together like concrete, wood, or metal.


Bolt Application


Bolts come in varying sizes. They are normally measured by:

  • Diameter, and

  • Number of threads per inch


The diameter refers to the width of the bolt shaft. It is measured in inches. The number of threads per inch is measured in threads/inch.


For example, a bolt size may be 5/16-18. The 5/16 tells you the bolt shaft diameter is 5/16ths of an inch. The 18 refers to the number of threads per inch. In this case, 18 threads per inch.


The manufacturer of a bolt will determine the optimal tightness of a bolt. If a bolt is tightened too much, it will snap. A bolt that is not tightened enough will be loose and not fasten the material.


The force required to turn a bolt is called torque. The required torque for tightening a bolt will be listed by the bolt manufacturer. When using bolts, be sure to apply the correct amount of torque to create a secure fastener.


The head of a bolt can be damaged by incorrect tool use or using the wrong tool. When the head of a bolt is damaged, it is a stripped bolt. A stripped head makes it very difficult for tools to grip the bolt head.


The threading on a bolt can also be damaged. Generally, you will be able to see threading that has been broken on the bolt. Do not use stripped or damaged bolts.


Washers


A washer is a thin circular piece of metal that goes underneath the head of a bolt. A washer helps spread the force of the bolt in a wider area. This prevents the bolt head from damaging the material.


Washers also prevent bolts from loosening over time. Washers prevent loosening by giving the bolt a flat surface to rest against. An uneven surface can cause the bolt to vibrate and loosen over time.


A lock washer is a type of washer that stretches so the bolt doesn’t become loosened over time. Unlike a regular washer, lock washers are not flat. Lock washers are great when a nut and bolt will be exposed to vibrations.


Bolts are a thick metal fastener. They can withstand very strong forces. Bolts can be easily added and removed from equipment Bolts are inserted into pre-drilled and tapped holes.



Nuts


This module will cover:

- What a nut is,

- Types of nuts, and

- Nut sizing Skip to quiz!


What is a Nut?

Recall that a bolt is a long threaded fastener. A nut is a fastener, used with a bolt, to fasten objects together.


A bolt will be inserted into a threaded hole. Once the bolt is through the material, a nut will be screwed onto the blunt side of the bolt. The material is stuck between the bolt head and the nut.


Types of Nuts


Some common types of nuts are:

  • Lock nuts,

  • Wing nuts, and

  • Hex nuts


Recall that strong vibrations can cause fasteners to loosen over time. As a machine vibrates, it creates small spaces between the nut and the object. The small space and vibration cause nuts to loosen over time. A lock nut (aviation nut) locks the threads in place to resist vibrational forces.


The inside of a lock nut has a nylon coating. When the nut is twisted onto the bolt, friction melts the nylon. When the nut is on the bolt, the nylon hardens again. The hardened nylon prevents the nut from loosening during vibration.


A wing nut has two large metal “wings” on each side of it. The wings allow you to easily turn the nut by hand. Wing nuts are common when you need to frequently change the tightness of a nut. Wing nuts are also great when a nut only needs to be hand tight.


A hex nut is a six sided nut with a threaded hole in the middle of it. Hex nuts are the most common nuts as they are easier to turn with a wrench.


There are two strengths of nuts:

  • Standard finished hex nut, and

  • Heavy duty hex nut

Each strength of nut is designed to handle anything below a specific load.


When the nut will not experience a large load, use a standard finished hex nut. Standard finished hex nuts are thinner, and cannot handle large loads. You can see a few finished hex nuts in the image to the right.


When the nut will experience a large load, use a heavy-duty hex nut. Heavy-duty hex nuts are thicker and can handle large loads. You can see a heavy-duty hex nut in the image to the right.


A stripped nut has a damaged head due to the use of the wrong tool. The head of a stripped nut has been rounded off. For example, a hex nut can become stripped when the edges become round.


Stripped nuts are very difficult to remove. Tools cannot grip the rounded edges of the nut. The picture to the right shows a stripped nut.


Recall that bolts can have coarse or fine threading. Recall that threading is metal ridges cut into the fastener. Just like a bolt, a nut can have coarse or fine threading.


A nut that has more space between threads is a coarse threaded nut. It is important to use a coarse threaded nut with a coarse threaded bolt.


Nut Sizing


Nuts are measured using the imperial system. Generally, you will see the thickness and width of a nut in inches. Inches are represented by the ” symbol. For example, 1” means 1 inch.


It is also common to see nut sizing written as a fraction. For example, 16/32” represents half an inch. 7/32” represents 7/32 of an inch.


Nuts are measured in three ways:

  • diameter,

  • flats, and

  • thickness


The diameter of a nut is the width of the hole in the middle of the nut. The diameter of a nut is labeled by the letter “D” in the image.


The flats of a nut refers to the length from one flat side of the nut to the flat side that is directly across from it. The flat distance is labeled as “K” in the image.

The thickness measures the height of a nut when it is laid completely flat. A thicker nut means a stronger nut. The nut thickness is labeled as “H” in the image.


To identify the correct nut size, first find the diameter of the bolt. Once you have the diameter, you can look up charts online that explain what nut size to use with the bolt. You can see an example of the chart to the right.


Be sure to choose a nut whose across flats measurement is larger than the bolt diameter. Choosing too small of a nut will prevent the nut from threading onto the bolt. Choosing too large of a nut will cause the nut to fall down the bolt.


For example, A bolt with a ¼” diameter would use a nut that measures 7/16” across flats. A bolt with a 5/16” diameter would use a ½” nut across flats.


Nut Application


To tighten a nut, you will twist it in a clockwise direction. To loosen a nut, you will twist it in a counterclockwise direction. Right tighty, lefty loosey is a great way to remember which direction to turn fasteners to tighten/loosen them.

To attach a nut to a bolt, start by using your hand to twist the nut clockwise onto the bolt. At a certain point, you will not be able to tighten the nut more by hand. At this point, you will use a wrench to finish tightening it. We will explain wrenches in a later topic.


To loosen a nut, you will start by using a wrench. Rotate the nut counter clockwise. You will not be able to loosen a tight nut with your hand. Once the nut is loose, you can use your hand to finish loosening the nut.


Nuts are used with bolts to fasten objects together. Nuts and bolts are designed for situations where the fastener will experience large loads. Choosing the correct nut and bolt creates a more secure hold.



Question #1: A nail has a ____, a smooth shaft, and a flat head.

  1. thread

  2. bolt

  3. point

  4. notch


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Answer: point

A nail has a point, smooth shaft, and a flat head. The point makes it easier for the nail to go into the material.


Question #2: Nails are better at resisting which type of force:

  1. Pulling forces

  2. Sliding forces

  3. Moisture forces


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Answer: Sliding forces

Use a nail to prevent sliding forces.


Question #3: Screws are better at resisting which type of force:

  1. Pulling forces

  2. Sliding forces

  3. Moisture forces


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Answer: Pulling forces

The threaded shaft of a screw increases the friction between the screw and the material. The friction makes the screw resistant to pulling forces.


Question #4: What is the importance of a pan head on a screw?

  1. It creates a seal, preventing any leaks.

  2. It creates a smooth surface

  3. It holds wooden objects closer together.

  4. It makes the screw easier to install.


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Answer: It creates a seal, preventing any leaks.

A pan head is rounded at the top with a flat surface underneath, which creates a seal to prevent leaks from gas or water.


Question #5: Which screw head looks like a six pointed star?

  1. Crosshead screw

  2. Torx screw

  3. Hex screw

  4. Slotted screw


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Answer: Torx screw

A torx screw has a six-pointed star shape, allowing for more contact points for a greater twisting force.


Question #6: Which is NOT a part of a nail?

  1. head

  2. shaft

  3. thread

  4. point

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Answer: thread

Nails consist of a head, a smooth shaft, and a point.


Question #7: Which screw creates threads when drilled into an object?

  1. Self-tapping

  2. Metal sheeting

  3. Wood

  4. Stripped


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Answer: Self-tapping

A self-tapping screw creates threads when screwed into an object, making it ideal for easy installation.


Question #8: Which type of bolt is the best for attaching large pieces of lumber?

  1. A lag bolt

  2. A hex bolt

  3. A hex tap bolt

  4. A carriage bolt


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Answer: A lag bolt

A lag bolt is a larger screw that is great for attaching large pieces of lumber.


Question #9: Which bolt has a round head and is good for attaching wood to metal or wood to wood?

  1. A lag bolt

  2. A hex bolt

  3. A hex tap bolt

  4. A carriage bolt


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Answer: A carriage bolt

A carriage bolt is the only bolt with a rounded head and it is good for attaching objects of different and like materials together.


Question #10: A bolt of size 1/4-16 has a diameter of

  1. 16 mm

  2. 1/4 inches

  3. 16 inches

  4. 1/4 mm


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Answer: 1/4 inches

The first number of a bolt measurement tells us the diameter in inches while the second number tells us the amount of threads.


Question #11: In the bolt measurement of 5/16”-15, what does the 15 stand for?

  1. Length of the bolt

  2. Diameter of the bolt

  3. Width of the head

  4. Threads per inch on the bolt


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Answer: Threads per inch on the bolt

The size 5/16” - 15 means the bolt has a diameter of 5/16” and has 15 threads per inch.


Question #12: A washer is used for which of the following?

  1. Tightening the nut quicker

  2. Spreading the force of the bolt head.

  3. Looking nicer when installed.

  4. Keeping the nut on the bolt.


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Answer: Spreading the force of the bolt head.

A washer distributes the force of the bolt head so it does not go through the material you are fastening.


Question #13: Which nut is best used when there will be high vibrations on the fastened object?

  1. Wing nut

  2. Stripped nut

  3. Self locking nut

  4. Hex nut


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Answer: Self locking nut

A self locking nut prevents the nut from becoming unscrewed due to high vibrations.


Question #14: Which nut is most easily turned by hand?

  1. Wing nut

  2. Stripped nut

  3. Self locking nut

  4. Hex nut


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Answer: Wing nut

A wing nut has two metal “wings” on each side of it that allows for easy turning by hand.


Question #15: Which nut size is the largest?

  1. 1/2” nut

  2. 1/4” nut

  3. 7/16” nut

  4. 17/32” nut


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Answer: 17/32” nut

When broken down into 32 parts of an inch, 1/2” = 16/32”, 1/4” = 8/32”, 7/16” = 14/32”, and 17/32” is already in terms of 32. This makes 17/32” the largest nut.


Question #16: A bolt has a diameter of 1/4”. What is the best-finished nut size, across flats, to use on the bolt?

  1. 1/16” nut

  2. 1/4” nut

  3. 7/16” nut

  4. 1” nut


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Answer: 7/16” nut

Bolt size 1/4" = 4/16”

  1. 1/16” = 1/16” Too small.

  2. 1/4 “ = 4/16” The same size.

  3. 7/16” = 7/16” Slightly larger.

  4. 1” = 16/16” Too large

A nut that is just slightly larger than the bolt will screw onto the bolt correctly.