Fasteners amp Hardware Fasteners are used in manufactured products for several basic purposes They simplify manufacture They simplify repairs They provide safety When selecting a fastener for a particular use consider these factors ID: 540102
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Slide1
Industrial Skills
Fasteners & HardwareSlide2
Fasteners are used in manufactured products for several basic purposes:
They simplify manufacture.
They simplify repairs.
They provide safety.Slide3
When selecting a fastener for a particular use, consider these factors:
Strength:
Will it hold the loads and pressures?Security:
Will it remain attached?
Cost:
Realistic?
Installation:
Appropriate for situation?
Skill:
Is specialized training needed?
Equipment:
Is specialized equipment needed and available?
Appearance:
If the fastener shows, which kind looks best?Slide4
Nails –
Most common method of fastening one wooden member to another.
Simplest & quickest.
May not result in the strongest of joints.
Many different sizes and various shapes of heads, points & shanks.
Each type designed for a particular purpose.
Drive nails at angles slanting toward or away from each other to get best holding power.
Nails are
designated
by “penny” size,
originally a term
which related to price
per hundred but now
signifies length. The symbol
for penny is the lowercase letter
“d”. Nail diameter increases with
length. Nails are now sold by the pound.Slide5
Screws
–
A large and important family of fasteners.
The most common types of screws are:
Sheet-metal screws
Machine screws
Set screws
Wood screws
“Mechanical devices for fastening things together. Essentially a cylindrical or conical piece of metal threaded evenly around its outside surface with an advancing spiral ridge and commonly having a slotted head: it penetrates only by being turned, as with a screwdriver.”
Use CategoriesSlide6
Wood Screws
Serve much the same purpose as a nail, but:
Provide greater holding power than a nail.
Screws can be easily removed and replaced.
Screws are neater in appearance and offer more decorative possibilities.
In addition to fastening pieces of wood together – the most common use of wood screws would be to anchor objects (hardware) to a wood surface. Slide7
Sheet-Metal Screws
Also called “Tapping Screws” or “Self-Threading Screws”.
Used to fasten light pieces of metal together or to attach covers, panels and other light parts.
These screws have sharp threads that can cut their own grooves into metal.
They come with “coarse” or “fine” threads and are usually case hardened to cut threads and withstand hard twisting forces.
Distinguishable from wood screws in that they are threaded all the way from the point to the head.Slide8
Machine Screws
Used for the assembly of metal parts and usually are driven into “threaded” holes rather than drawn tight with nuts.
Like all screws, there are many head designs to choose from.
Machine screw threads are also designated by the number of threads per inch, just like bolt threads:
A 6-32 machine screw has a #6 body diameter and 32 threads per inch of length.
Most machine screws are fully threaded to the head.Slide9
Set Screws
Frequently used to hold a knob, collar, pulley or gear to a rotating shaft.
There are a variety of “head” or “point” styles, each best suited for its job.
Generally made of high-strength material and are heat treated.
Not an especially strong type of fastening – depend on friction and “shear” to hold parts together.Slide10
Once you have decided to use screws, in addition to the use category, you must consider four things before ordering.
Type of head
Material made of
The length
The diameterSlide11
The “type of head” should include both the
“shape”
and the
“style”.
Pan Head
Truss Head
Hex Head
Flanged Hex Head
Screw Head “Shapes”
Screw Head “Styles”Slide12
The most common “material screws are made of” is steel.
If the fastener is exposed to the “weather” – steel alone does not offer much protection against the harmful effects of corrosion.
Coatings offer more protection.
Steel Blued
Zinc Coated
Chromium
Galvanized
Nickel
Silver Plate
Gold Plate Marine Applications may require different metals and/or materials.Stainless SteelAluminum
CopperBrassBronzeSynthetic Materials (Plastic or Nylon)Slide13
The “length” of screws commonly range from ¼ inch to 4 inches. Shorter or longer lengths are generally special order items.
(Metric lengths are also available)Slide14
Screw diameters can be expressed by the “gauge” number or by the fraction of an inch.
(Metric diameters are expressed in mm)Slide15
American Screw Gauge
Sizes are designated by length in inches
(millimeters).
Diameters less than ¼ inch (6 mm) use gauge number. Diameters greater than ¼ inch use fractions of an inch.
Wood screws are an exception to this rule in that they generally go up to a #20 gauge (
21/64
”).Slide16
Bolts, Cap Screws, Nuts & Washers
Nomenclature of bolt-type fasteners tends to be confusing.
Bolts are usually used in plain holes drilled through the parts being fastened.
Bolts are generally held in place with a mating nut.
When the nut for any bolt is turned down on wood, always use a flat washer under the nut.
Cap screws are normally used in threaded holes, without a nut.Slide17
Machine Bolts/Cap Screws
Machine bolts
have square or hexagonal heads.
Installed with a wrench.
Usually used if the parts to be joined are made of metal.
Cap screws
generally look just like a machine bolt.
Slightly different application.
Screwed into threaded holes rather than being used with a nut.Slide18
Round-Head Bolts
Commonly used to fasten wood parts.
Most have a square neck under the head.
Also used to fasten steel parts with square punched holes.
A
Carriage Bolt
is the most common type of round-headed bolt to be used when working with wood.
A
Plow Bolt
has a flat, tapered head that fits into a countersunk hole – primarily used with metal parts.
Used in the marine industry for attaching cutters and other parts to dredges.
Plow Bolt
Carriage BoltsSlide19
Stove Bolts
are available with the same types of head designs as wood screws, in diameters from 5/32” to 1/2” and in lengths from 3/8” to 6 inches.
Studs
are another type of threaded fastener, which have no head at all and is merely a steel rod with threads on both ends.
One end is screwed into a part, other parts are assembled over the studs and screwed in place with a nut.Slide20
Other “ Bolts”
Some fasteners are referred to as bolts but are actually screws.
A
Lag Bolt is really a “heavy-duty screw” with a square or hex head.
Designed to be driven with a wrench.
Available in lengths from 1” to 6” and diameters from 1/4” to 1/2”.
A
Hanger Bolt
is a fastener that has wood screw style threads on one end and machine threads on the other.
No head on this type of “bolt”.
Designed to be a hidden fastener.Slide21
Sizes and Descriptions
Threads
– External helical ribs on the body of a bolt at the end opposite the head.
The
diameter
of a bolt is determined by the diameter of the crest of the threads.
The
length
of most bolts (or machine screws) is determined by the measuring from the bottom of the head to the end of the threads.
Flat head bolts are measured from the threaded end to the top of the head.The Head Size determines what size wrench or socket must be used to turn or hold the bolt or nut.A square or hexagonal bolt head is measured across the “flats”.Example – A ¾” wrench is needed to turn a ½” diameter bolt head.Slide22
Threads
Threads
–
External
helical ribs on the body of a bolt. Usually a bolt “mates” with
internal
threads of a nut.
The top of the rib is called the
crest, or thread tip.Bottom of the groove is called the thread root
.Threads are measured by counting the number per inch. (Metric threads are measured by the distance between threads – pitch – in mm)
Thread gauges are available that match threads against those on the gauge.Slide23
The type of threads that are used for most applications are coarse with deep grooves.
Some threads are finer, with shallower grooves.
Bolts with fine threads are used only under special conditions – such as when the parts being fastened have thin walls.
Bolts and screws normally have
right-hand threads.
Turned to the right (clockwise) when tightened.
Occasionally, bolts, screws and nuts with
left-hand threads
are needed.
Turned to the left (counter-clockwise) when tightened.Slide24
American National Standards Institute
(
ANSI )
There are carefully controlled standards for threading bolts and nuts.
ANSI establishes such things as the angle of threads, the depth of the root and the manufacturing tolerances (fit) which are referred to as the
“Unified Screw Thread Standards”
.Slide25
International Organization for Standardization
(
ISO )
Established standards for classifying metric bolts and screws.Slide26
Grades and Head Markings –
Inch-Series
The kind of steel bolts and screws are made of and the treatment they receive during manufacture determine their strength.
The Society of Automotive Engineers (SAE) has established standards for classifying inch-series bolts and screws into grades, based on their tensile strength.
Markings consist of radial “slashes”.
High-quality inch-series bolts and screws ¼” and larger have them.
Grade 5 or better hardware should be used in most situations.Slide27Slide28
Grades and Head Markings -
Metric
The kind of steel bolts and screws are made of and the treatment they receive during manufacture determine their strength.
The International Organization for Standardization (ISO) has established standards for classifying metric bolts and screws into property classes based on strength.
Numbers on the head indicate property class.
High-quality metric bolts and screws 4mm and larger have them.
Class 8.8 or better hardware should be used in most situations.Slide29Slide30
Nuts and Washers
Nuts have coarse or fine
internal threads
that correspond to the threads of a bolt and are designed to “screw” onto the bolt to fasten it in place.
A great variety of shapes and sizes for standard and special applications.
Threads per inch or distance between threads can be determined with a thread gauge just like bolt threads.
Nuts have three important dimensions:
Thickness
Distance across the flatsInside diameter (same as that of the bolt with which it is to be used).Slide31
Jam Nuts
– Used to lock a threaded part in place.
Castellated and Slotted Nuts
– Secure a nut in place so it can’t possibly come loose.
Self-Locking Nuts
– Stay firmly in place even with constant vibration.
Many other types of nuts available for special uses.
Hex and Square Nuts
The most common nuts, generally made of steel and are hexagonal or square in shape.Slide32
A plain
washer
is simply a steel disk with a hole through the center.
Like bolts and nuts the may be manufactured with a variety of different materials They help distribute the load over an area larger than the head of the bolt or nut, thus reducing the stresses that would otherwise exist.
Plain washers are identified by their outside diameter and the diameter of the hole, which is the bolt size rather than the actual diameter of the hole.
The washer thickness varies with the size of the washer.Slide33
Lock washers are frequently used to keep nuts and bolts tight, especially when they are subject to vibration.
Helical Spring Washers
– Made of tough spring steel. They are split and one end of the split is bent up. When the nut is tightened, the section of the washer that is bent up “bites” into the nut and the fastened part.
Toothed Lock Washers – Has many sharp, heat-treated teeth to dig into the surfaces pressing against it.
Many other types of washers are available for special uses.