Wood Fasteners - PowerPoint by linzhengnd

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									Wood Fasteners




                 1
                            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.



                                                                         2
    Nails
A nail is a pin-shaped, sharp object of hard
metal, typically steel, used to fasten things
together (usually wood).




                                          3
                                 Nails--continued
                                           Nails are divided into 5 common types:
                                           1. Common
                                           2. Box
                                           3. Duplex
                                           4.     Roofing
                                           5.     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.
                                                                                  4
    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.




                                                               5
                        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.




                                                               6
   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.




                                                                   7
           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.




                                                                        8
 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”.



                                                                    9
     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?


                                    10
Screws




         11
                            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.



                                                                       12
                          Screws--Heads




Different styles of screw heads are available to meet different job
requirements.




                                                                      13
                           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

                                                                14
            Screw Drive Sockets




This is just a few of the many types of drivers
used for screws.




                                                  15
                         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.




                                                                    16
                            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.


                                                                            17
Bolts




        18
                               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



                                                                                19
                               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.




                                                                           20
                                  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.




                                                                            21
          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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