Transcript Wood Fasteners - Oklahoma State University–Stillwater

Wood Fasteners
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Introduction
When constructing a building, the individual pieces of wood (members) must
be connected together.
Early buildings were assembled with pegs.
Pegs were gradually replaced by
square (hand cut) nails.
With the invention of nail making
machines, wire nails became
available.
Modern wooden buildings are assembled using nails, threaded fasteners,
and glues/adhesives.
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Nails
A nail is a pin-shaped, sharp object of hard
metal, typically steel, used to fasten things
together (usually wood).
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Nails--continued
Nails are divided into 5 common types:
1. Common
2. Box
3. Duplex
4.
5.
Roofing
Deformed shank
1.
Nails are sized according to Penny number, 2d to 40d.
2.
Penny originally referred to the number of that size of nail that could be
bought for a penny.
3.
Today it is the reference to diameter and length.
4.
The larger the number the larger the nail.
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Common Nails
1. Common Nails are one of the oldest forms of fasteners.
2. Common nails of the same size will have a larger diameter
shank than box nails.
3. Common nails are used for most building framing.
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Box Nails
• Box nails were developed to
reduce the splitting of the wood
when nailing smaller pieces of
wood to from boxes and crates.
• Box nails are about the same length as common nails for
the same size.
• Box nails are smaller in diameter for the same size as
common nails, which reduces the potential for splitting.
• For the same diameter, box nails will have a smaller head.
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Duplex
Nails
• Duplex Nails are heavy-duty framing
nails.
• They are used in temporary applications.
• Their second head prevents them from
being hammered flush with the surface.
• When the job is done, simply remove the nail by prying it out by the
upper head.
• One common use is concrete forms.
• Protruding head can be a safety hazard.
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Roofing
Nails
Roofing nails are designed to attach
softer materials, such as tar paper and
asphalt shingles to wood.
They have wider head, for the diameter of
the shank, spreads the force over a greater
area.
Many different styles are available.
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Deformed Shank Nails
• Two primary types.
– Spiral groove
– Annular groove
Common, box,
roofing, flooring
and many other
types of nails are
available with
deformed shanks.
What is the advantage of deforming the shanks?
Common name for larger size angular shank is “pole barn nail”.
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Brads
• Brads are small wire type
nails used for doing trim work
and fastening other thin
materials.
• They come in a variety of
diameters, lengths and head
shapes.
• Pre-drilling is recommended
in hard woods because they
bend quite easily.
Where would brads be used?
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Screws
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Screws
• Screws are the second
most popular means of
fastening wood.
• They are available with
many different types of
heads, lengths and
driver sockets.
Wood screws are sized according to diameter of the shank (wire gauge
number) and length.
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Screws--Heads
Different styles of screw heads are available to meet different job
requirements.
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Screw-Flat & Oval
The flat head and oval require three separate operations for
installation.
1. Drill pilot hole to the depth of the threads.
2. Drill clearance hole through the first board.
3. Counter sink the surface.
Is there an easier way?
Yes. Pilot drill
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Screw Drive Sockets
This is just a few of the many types of drivers
used for screws.
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Lag Screws
• Lag screws are used to install wood or metal members to
wood.
• Primarily used when the strength of a bolt is needed, but a nut
can not be used.
• Lag Screws are installed by drilling a clearance hole through
the first member and pilot hole into the second board the depth
of the threads.
The lag screw is then
threaded into the hole.
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Lag Screw--cont.
• Lag screws and wood screws
must be installed correctly for
maximum load holding.
• The shank must be equal to the
thickness of the first member
being fastened.
• The pilot hole for the first member
must be large enough to install
the screw with minimum effort.
• The pilot hole for the threaded portion must be sized to provide a
good grip for the threads, but not so tight that the threads on the
screw jam in the hole.
• Usually requires some trial and error to get the right size.
• Size will depend on the size of the screw and the hardness of the wood.
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Bolts
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Machine Bolt
•
•
•
A Machine bolt is a heavy-duty
fastener.
When used correctly, will support
and/or sustain the largest sheer or
tension load.
Several small bolts will support a
load better than one large bolt.
 A bolt is generally inserted through a pre-drilled in the parts that are to
be assembled.
 Tightening and loosening of the bolt is done with a nut.
 Washers should be used when attaching wood to prevent bolt from
pulling through the wood.
 Thread pitch is standardized as NC or NF.
 Metric sizes are available
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Carriage Bolts
•
•
•
•
Carriage Bolts are easily recognizable
because of their round head and short section
of square neck.
The round head is set flush with the surface of
the wood.
The square neck prevents bolt from rotating
when nut is tightened.
Usually difficult to remove because the wood shrinks away from the square
neck and then there is no way to prevent the bolt from turning.
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Washers
Lock washers are designed to
prevent the nut from loosening itself
by applying back pressure.
Common types:
Split
Internal tooth
External tooth
Flat Washers are used to spread the
clamping force of a bolt over a larger surface
area.
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Hex Nuts
• Hex nuts are used with bolts to fasten structural members
together.
The threads can be NF (national fine) or NC
(national coarse)
Square nuts are still available and used with
wood because of their larger contact area.
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