Screws

Screws provide more strength and holding power than nails. Additionally, if something needs to be disassembled, screws can easily be removed. While the advantages of screws are pretty self evident, have you ever wondered how many types of screws exist?

Like nails, screws are available with different coatings to deter rust. They are manufactured with four basic heads and different kinds of slots. Flat head screws are almost always countersunk into the material being fastened so the head of the screw is flush with (or lower than) the surface. Oval head screws are partially countersunk, with about half the screw head above the surface. Round head screws are not countersunk; the entire screw head lies above the surface. Fillister head screws are raised above the surface on a flat base to keep the screwdriver from damaging the surface as the screw is tightened.

Beyond these core types of screws, there are many others to explore, each with distinct uses. In this article, we'll cover as many screw types as possible, including the best options for simple home repairs as well as tips on how to leverage each type.

Drilling Screws and Pilot Holes

Most screws have slot heads and are driven with slotted, or standard, screwdrivers. Phillips-head screws have crossed slots and are driven with Phillips screwdrivers. Screws are measured in both length and diameter at the shank, which is designated by gauge number from 0 to 24. Length is measured in inches. The length of a screw is important because at least half the length of the screw should extend into the base material.

Here's a tip: To prevent screws from splitting the material, drill pilot holes into the material before the screws are driven. A pilot hole creates the vessel for a screw to enter without damaging the surrounding material.

From Wood Screws to Machine Screws

For most home repair purposes, wood screws will suffice. Sheet metal screws, machine screws, and lag bolts also come in various types. If you're trying to replace one of these screws, take an old screw with you to the hardware store. The following are some of the most common screw types:

Wood Screws

Wood screws are usually made of steel, although brass, nickel, bronze, and copper screws should be used if there is potential for corrosion. For optimum wood screw performance, you need to drill first.

Sheet Metal Screws

Use this type of screw to fasten pieces of metal together. Sheet metal screws form threads in the metal as they are installed. There are several different types of sheet metal screws. Pointed pan head screws are coarse-threaded; they are available in gauges from 4 to 14 and lengths from 1/4 inch to 2 inches.

Pointed pan heads are used in light sheet metal. Blunt pan head screws are used for heavier sheet metal; they are available in gauges from 4 to 14 and lengths from 1/4 inch to 2 inches. Both types of pan head screws are available with either plain or Phillips-head slots.

Round Head Screws

Partial-tapping round head screws have finer threads; they can be used in soft or hard metals. They are available in diameters from 3/16 inch to 11/4 inches. Self-tapping screws of the round head variety are used for heavy-duty work with thick sheet metal and are available in diameters from 1/4 inch to 2 inches and in lengths from 1/8 to 3/4 inch. Both types of round head screws are available with either plain or Phillips-head slots. Plus, they are the ideal self tapping screw.

Machine Screws

Machine screws are blunt-ended screws used to fasten metal parts together. They are commonly made of steel or brass. Like other fasteners, machine screws are also made with coatings -- brass, copper, nickel, zinc, cadmium, and galvanized -- that help deter rust.

Machine screws are manufactured with each of the four basic types of heads -- flat head, oval head, round head, and fillister head -- and with both plain and Phillips-head slots. They are typically available in gauges 2 to 12 and diameters from 1/4 inch to 1/2 inch and in lengths from 1/4 inch to 3 inches.

Lag Bolts

For light work, lead, plastic, or fiber plugs (called anchors) can be used to hold screws. But for larger jobs and more holding power, lead expansion anchors and lag bolts are used. Sometimes called a lag screw, a lag bolt is a heavy-duty fastener. They are driven with a wrench and are used primarily for fastening to masonry materials or wood framing. The anchors are inserted into holes drilled in the masonry, and the lag bolts are driven firmly into the anchors.

Discover Countless Types of Screws

The world of screws extends far beyond the basic wood and machine screws, encompassing a diverse array of types each suited to specific applications. Self-drilling screws, for instance, streamline operations by combining drilling and fastening into one, eliminating the need for a pre-drilled hole.

When a secure connection to a nut or tapped hole is required, machine screws and hex cap screws offer reliable solutions. For materials that need precision threading, thread cutting screws make an excellent choice, creating a threaded screw path as they are driven in.

In woodworking, pocket hole joinery, with its specialized screws featuring a smooth shank and sharp tip, allows for strong, hidden joints. Finally, threaded hole fastenings, which are fundamental in mechanical applications, can be achieved with an array of screw types, each designed to meet specific strength, material, and environmental requirements.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.

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