wood fasteners

8/4/2019 Wood Fasteners

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Wood Fasteners

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Introduction

Modern wooden buildings are assembled using nails, threaded fasteners,and glues/adhesives.

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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 makingmachines, wire nails becameavailable.


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NailsA nail is a pin-shaped, sharp object of hard

metal, typically steel, used to fasten thingstogether (usually wood).

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Nails--continued

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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.

Nails are divided into 5 common types:

1. Common

2. Box

3. Duplex

4. Roofing

5. Deformed shank


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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 are about the same length as common nails forthe same size.

Box nails are smaller in diameter for the same size ascommon nails, which reduces the potential for splitting.

For the same diameter, box nails will have a smaller head.

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Box nails were developed to

reduce the splitting of the woodwhen nailing smaller pieces ofwood to from boxes and crates.


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DuplexNails

When the job is done, simply remove the nail by prying it out by theupper head.

One common use is concrete forms. Protruding head can be a safety hazard.

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Duplex Nails are heavy-duty framingnails.

They are used in temporary applications.

Their second head prevents them from

being hammered flush with the surface.


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RoofingNails

Roofing nails are designed to attachsofter materials, such as tar paper andasphalt shingles to wood.

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They have wider head, for the diameter of

the shank, spreads the force over a greaterarea.

Many different styles are available.


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DeformedShank Nails

Two primary types.

Spiral groove

Annular groove

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Common name for larger size angular shank is pole barn nail.

Common, box,roofing, flooringand many othertypes of nails areavailable withdeformed shanks.

What is the advantage of deforming the shanks?


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Brads

Brads are small wire typenails used for doing trim workand fastening other thinmaterials.

They come in a variety of

diameters, lengths and headshapes.

Pre-drilling is recommendedin hard woods because theybend quite easily.

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Where would brads be used?


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Screws

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Screws

Screws are the secondmost popular means offastening wood.

They are available withmany different types of

heads, lengths anddriver sockets.

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Wood screws are sized according to diameter of the shank (wire gaugenumber) and length.


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Screws--Heads

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Different styles of screw heads are available to meet different jobrequirements.


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Screw-Flat & Oval

The flat head and oval require three separate operations forinstallation.

1. Drill pilot hole to the depth of the threads.2. Drill clearance hole through the first board.3. Counter sink the surface.

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Is there an easier way?

Yes. Pilot drill


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Screw DriveSockets

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


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LagScrews

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 throughthe first member and pilot hole into the second board the depth

of the threads.

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The lag screw is thenthreaded into the hole.


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Lag Screw--cont.

Lag screws and wood screws

must be installed correctly formaximum load holding.

The shank must be equal to thethickness of the first memberbeing fastened.

The pilot hole for the first membermust be large enough to installthe screw with minimum effort.

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The pilot hole for the threaded portion must be sized to provide agood 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 ortension load.

Several small bolts will support a

load better than one large bolt.

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A bolt is generally inserted through a pre-drilled in the parts that are tobe assembled.

Tightening and loosening of the bolt is done with a nut.

Washers should be used when attaching wood to prevent bolt frompulling through the wood.

Thread pitch is standardized as NC or NF.

Metric sizes are available

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CarriageBolts

Carriage Bolts are easily recognizable

because of their round head and short sectionof square neck.

The round head is set flush with the surface ofthe wood.

The square neck prevents bolt from rotating

when nut is tightened.

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Usually difficult to remove because the wood shrinks away from the squareneck and then there is no way to prevent the bolt from turning.


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Washers

Flat Washers are used to spread theclamping force of a bolt over a larger surface

area.

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Lock washers are designed toprevent the nut from loosening itself

by applying back pressure.

Common types:

Split

Internal tooth

External tooth


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Hex Nuts

Hex nuts are used with bolts to fasten structural memberstogether.

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The threads can be NF (national fine) or NC(national coarse)

Square nuts are still available and used withwood because of their larger contact area.


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