Holding it All Together with Nails, Screws and Bolts

By Paul Bianchina

Whatever project you're about to undertake, the one thing you know for sure is that something needs to hold all the parts together - and it only takes one trip through the lumber yard to become confused with all of the choices in nails, screws, and bolts. So, for future reference, here's a basic do-it-yourselfer's guide to some of the more common fasteners on the store shelves.

Nails

Nails are sized by an antiquated system know as "pennies," abbreviated by the lower case letter "d." The larger the "d" number is, the longer and heavier the nail is. Nails shorter than 1 inch (2d) are commonly referred to as brads, and nails that are longer than 6 inches (60d) are referred to as spikes.

Besides their length, nails are designated as follows:

Head type: The most common nail head is flat, giving you a bigger target for the hammer, or countersunk, also called a sinker, which is flat on top and slightly tapered on the bottom. Flat heads may also be smooth-faced or slightly "checkered" on top, which lessens the hammer's tendency to slip off the head.

Other common heads include finish nails, with a very small, tapered head that is easier to sink into the wood and conceal; siding nails, which have a head diameter roughly between the flat and finish sizes; drywall nails, with a cupped head to hold joint compound; and duplex nails which have two heads, one above the other, making them easy to remove for temporary tasks like form building.

Material or coating type: Most nails are made of steel, although stainless steel, aluminum, copper, and other materials are also used. Steel nails may also be galvanized - dipped or otherwise coated with zinc for rust resistance - or they may be covered with a vinyl coating that makes them easier to drive and more resistant to pull-out for use in many framing applications.
Shank type: Besides the common smooth shank, there are actually several other shank types as well. Some of the more common - all designed to increase the nail's resistance to pulling free of the wood - include ring-shank, with small rings cast into the shank of the nail; screw-shank, with a spiraling shank similar to a screw; and barbed, which has tiny protruding barbs.

A single nail may often have a grouping of these terms that are used to describe it. For example, one of the most common framing nails is the 16d VC sinker, meaning it is 16d in length (3 ½-inch), vinyl coated (VC), and has a slightly tapered head (sinker).

Screws

If nails confuse you, that's nothing compared to the number of screws available. Screws, like nails, are known by several characteristics, including:

Head type: Common types include flat-head, which is flat on top and tapers down to the shaft, designed to sink into a matching cone-shaped hole in the wood; round-head, with a curved top; and pan-head, which is flat on top but does not taper down like a flat-head, and is not intended for countersinking.
Driver type: This refers to the type of tool required to install the screw, and includes: slotted, for a flat-bladed screwdriver; Phillips, which requires a star-pointed Phillips-head screwdriver; square-drive, with a square, recessed hole that requires a matching square-head screwdriver; Allen, similar to a square-drive but with a six-sided hole that requires a matching Allen wrench; TORX^®, which is a multi-sided recessed hole that again requires a special matching driver; and hex-head, which has a raised hexagonal head and is installed using a nut driver or socket wrench.
Thread type: A standard wood screw has a relatively thick shaft that is straight and unthreaded near the head and then tapers to a sharp point, along with a fairly deep thread that is designed to grip wood tightly. Machine screws have a uniform shaft diameter and a blunt end, with smaller, less angled threads, designed for use with a matching nut or threaded hole. A drywall screw, which is also popular for woodworking, has a flat head, a slender shaft, and a steeply-pitched, aggressive thread design which tapers to a very sharp cutting point that pulls quickly into wood or light-gauge sheet metal. Sheet metal screws have a gentler thread angle and are designed for use in sheet metal with a pre-drilled hole. Self-tapping screws have a special point that resembles a drill bit and are capable of cutting their own pilot hole in light gauge sheet metal.

Bolts

For construction use, there are three common types of bolts:

Hex bolts: Hex bolts have a deep, machine-type thread and a hexagonal head for use with a wrench or socket. They are used with a matching nut or matching threaded hole.
Carriage bolts: These resemble a hex bolt but have a half-round head that cannot be gripped by any type of wrench. Immediately below the head the shaft is square, and when the bolt is driven into a predrilled hole in wood the square section will wedge in the hole. This type of bolt is used with a matching nut, and is designed for applications where security or a smooth finished look is important.
Lag bolts: Lag bolts resemble a large wood screw, with a hexagonal head and a tapered, threaded shaft that ends in a point. They are only used in wood, and are installed into a pre-drilled pilot hole using a wrench or a socket.

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