Long before wood screws were a thing, carpenters were using adhesives, nails, and wood joints to fuse to or more segments. Each technique had its disadvantages and advantages. However, the inception of this new wood fastener introduced a new way of fastening and mounting.
These work with hardwood, chipboard, MDF, and softwood. Several types are available in the market, which have different features. Most have safety features, such as the following:
- Avoid wood splitting through shanks
- Effective driving through twin threads
- Sharp tips will no longer need you to pre-drill
You can purchase these items in different head shapes and drive types. Each one is best for a specific application. Manufacturers initially use steel or bras to produce these items. The shaft has an increasing thickness from the tip to the head.
These fasteners have several thicknesses and lengths. We are covering everything you need about wood screw size charts, types, and some practical applications.
Screw sizing explained
If you search for sizing, you will see different lengths, gauges, and threads, confusing several people. Take extra care while choosing because one wrong choice may ruin the entire application. Here are three parts worth keeping in mind.
The main measurements fall under three categories – threads per inch (TPI), length, and gauge. These are the measurements you will often encounter when shopping for these items.
The gauge is the first number, referring to the thread diameter. Others also refer to it as major diameter. The size labels #0 to #14 have a major diameter of less than 0.25 inches, while greater than #14 are in fractions of an inch.
Each gauge size has an equivalent decimal value. For example, a #1 gauge is 0.073 inches. The size has an incremental value of 0.013 inches per gauge.
Aside from the major diameter, we also have the minor. It refers to the width measurement below the threaded part. We call the unthreaded portion the shank diameter.
The length of the shaft is the next important measurement. The part of it that drives through a surface is the shaft length. You measure from the tip to the top of the head for types that can drive beneath the surface. These countersinking types include the bugle-head, trim-head, and flat-head.
You measure from the head’s bottom to the tip for types you cannot drive beneath the surface. Some examples of this non-countersinking are round, hex, button, pan, and truss. One exception to it is the oval head, which classifies as partial-countersinking.
Threads per Inch (TPI)
The TPI refers to the thread count within a one-inch section. It occasionally follows the gauge with a hyphen. A label that says #8-10 means a #8 gauge and ten threads per inch.
Length of screws
Several lengths are available in the market. The largest size most manufacturers produce is size 32. It has a shank diameter of 0.5 inches and a head diameter of one inch. On the other hand, the small size most manufacturers have is size 0000, with a shank diameter of 0.054 inches and a head diameter of 0.108 inches.
Generally, a head reduction of 0.0028 inches and a shank reduction of 0.0014 inches happens until it reaches size one. The diameter reduction is 0.006 inches and 0.003 inches after it passes this point, respectively.
The table below shows the typical measurements. Slight variations are possible depending on the type.
|Screw Gauge||Head diameter (mm)||Shank diameter (mm)|
|Length (Inches)||Length (mm)|
Types of wood screws
Not all wood screws are a one-type-fits-all. Each variety has a recommended application. For example, a flat head is best for cabinetry. However, a hex head is best for roofing and flooring. The following are the common wood screws in the market.
As the name suggests, there is a hexagonal shape on the head of this variety. It helps you drill faster while reducing the chances of stripping. The most common applications are on bearing structures, roofs, and floors.
We recommend the following products for this type.
Heavy Duty Hex Head
These screws are intended to support loads heavier than those carried by hex-head structural screws. Their washer heads are wider than the others. When considerable tension is present, they first prevent the head from sinking into the material. Secondly, the wider head improves grip on the surface. These screws have a diameter ranging from 66 to 87 millimeters.
We recommend the following heavy-duty products.
Stainless Steel Hex Head
The stainless steel type is corrosion-resistant, allowing you to use it in places high in moisture. A hex head prevents it from stripping out during insertion or removal.
The following items are our recommendations.
The difference between the standard hexagonal and flat-head varieties is the absence of angled edges, reducing screw splinters. The best application is finishing wood cabinetry. These have a tighter thread, allowing more grip and higher resistance.
The following are our recommendations.
We use the standard type to fuse wood pieces. The head is smooth, and the shank has threads. The flat type provides a finish after driving into the wood. You will find it cheaper and available in several varieties.
We recommend the following products for this type.
The pocket is famous for its self-tapping ability. The wide head attaches to the flat shoulder.
We recommend using this with pocket holes. Please refrain from using a standard type because it will split the wood. The square drives you will find the help you place it easily.
We recommend the following products for your pocket screw needs.
The deck’s best application is outdoors. Manufacturers use copper or steel, allowing resistance from corrosion. The shanks on these have deep threads and sharp tips, making it easy to drive through the surface of the boards.
We can use the deck type on hardwood or softwood applications. They are most useful for people living in coastal areas, where weather conditions are more unpredictable and harsher. This type can withstand all weather conditions while providing a firm and secure bond.
We recommend the following deck types.
Drywall is the cheapest among all the types, which most people use for woodwork. The thread runs through the entire length and has a thin shank. However, they are not very durable. We do not recommend using them in hardwood.
The following are our recommendations.
Wood screw size chart
Selecting the suitable size is equally important as choosing the right length. The thickness must also fit the width of the material. Moreover, we recommend ensuring it can support the load.
By Head Drive Type
The main head types are as follows.
- Slot-head – This is the most common variety among all the head types. You can use a flat-head screwdriver to turn the head through the material.
- Robertson or Square Drive – The Robertson has a few advantages over the Phillips. The square drive features a square head, reducing the chances of slippage. You will usually find it in pocket screws.
- Phillips – The Phillips is more functional than the slot-head variety. It works well on different wooden materials, allowing you to insert it with minimal risks. You may encounter slipping when driving it through the final section.
- Starhead – There has been an increase in popularity for star-head over the last few years. It is popular among woodworking applications because of its reliability. It can also accommodate more torque.
By Material Type
Manufacturers use steel, stainless steel, and brass for these items. They have different applications. You can quickly drive these into a board with minimal stripping.
- Steel – Steel is the most common material available. Pre-drilling is not a requirement to fit these into most wooden applications. Hardened steel or zinc-plated offer more durability and corrosion resistance.
- Stainless Steel – The main advantage of using stainless steel is resistant to moisture. These are available in different heads, depending on the application.
- Brass – These have an attractive physical appearance. Most carpenters use this as an alternative to steel in places with naturally occurring acids. They are best for outdoor applications because of their high levels of corrosion resistance.
The table below demonstrates a few of the sizes available.
|“A” Flat Head||“A” Flat Head||“A” Pan Head||“A” Pan Head||“A” Pan Head||“A” Round Washer Head||“A” Round Washer Head||“A” Round Washer Head||“B” Body Dia||“B” Body Dia||“C” Thread Dia||“C” Thread Dia|
|Size||Min||Max||Min||Max||T max||Min||Max||T max||Min||Max||Min||Max|
How to choose the right wood screw: 4 mistakes to avoid
Choosing the right one is essential in every application. Each size has its uses. Generally, choose a thickness that can enter at least half of the material.
Incorrect material and grade
Each type has a distinct property appropriate for a specific application. Stainless steel is corrosion-resistant, while grade 316 stainless steel has higher resistance from corrosion. It makes it excellent for saltwater applications.
Putting two or more reactive metals together will weaken their integrity. Putting stainless steel and aluminum together in salt water will make an unstable balance, weakening the material and leaving it susceptible to rust.
Mixing metric and imperial sizes
Always check the sizes before installing or purchasing your materials. Do not mix metric readings with imperial readings or vice versa because these will create inaccuracy and confusion with your measurements.
Wrong driver size
Using the correct driver size reduces deformation chances and over-screwing. A loose driver increases the chances of stripping and camming out.
The following are the common ones available in the market.
#6 screw diameter
Gauge #6 is not the smallest diameter in the market but is common among small objects. It has a thread size of 0.13 inches and a length ranging from 0.5 to 1.5 inches. The typical applications are toys, drawer slides, light fixtures, and hinges.
Recommendation – SG TZH #6 Self-Tapping Wood Screw
#8 screw diameter
Gauge #8 is the most common size in the market. It has a wide application, making it common in several wooden objects. Items such as cabinets, furniture, and other light constructions use the #8. These have lengths ranging from 0.625 to three inches.
Recommendation – Bolt Dropper #8 Stainless Steel
#10 screw diameter
Gauge #10 are for larger and heavier objects, which you will find in many construction jobs. Moreover, you will also find it on the patio and outdoor furniture. These have a thread diameter of 0.19 inches.
Recommendation – Deck Plus #10
#12 screw diameter
Gauge #12 works great on woodworking projects, specifically when connecting two or more points. The one we recommend below is 100% stainless steel, which is resistant to rust.
Recommendation – LIONMAX #12 Woodworking Kit
#14 screw diameter
Gauge #14 is excellent for outdoor and indoor use. The stainless steel material prevents corrosion from building up around the shaft.
Recommendation – Bolt Dropper #14 Stainless Steel
6/32 screw diameter
It has a black phosphate coating, enabling higher resistance to corrosion and rust. Ideally, we recommend using it in renovations and fixing wooden flooring. It also works with plastic and soft metals.
Recommendation – MR SCREWS #6-32 Stainless Steel Self-Tapping
8/32 screw diameter
These have sharp tips but are not corrosion-resistant. We recommend using it indoors and away from moisture and direct contact with water.
Recommendation – Snug Fasteners #8-32 Black Phillips Truss Head
The 4-40 size is ideal for different applications. It includes chipboards, fiberboards, hardwoods, and softwoods. Most manufacturers make these using a single thread, allowing for easier and quicker insertion. It is also not limited to wooden applications because it works with metal or plastic. Those using zinc coating or a stainless steel material are unlikely to rust.
10/32 screw diameter
The 10-32 has 32 threads per inch (TPI). It roughly translates to a diameter of 0.1875 inches. We recommend using the 10-32 in indoor and outdoor woodworking of:
- door hinges
- and fence panels.
You can use it outdoors if you have a corrosion-resistant screw. Otherwise, we recommend staying away from moisture and water.
2/56 screw diameter
The 2-56 has around 56 threads per inch (TPI). This type is not very common in woodworking. However, you will rarely find it in small objects or items.
10/24 screw diameter
The 10-24 diameter is for general woodworking purposes. Some manufacturers produce corrosion-resistant items that you can use in wet and dry applications. Please check with the manufacturer before taking further action.
A flat-head type will work great in furniture because of its flushed design. We also recommend using it in fences and decks.
Recommendation – Hillman #10-24 Galvanized Wood Screw
M3 screw diameter
The M3 size is excellent for woodworking jobs and do-it-yourself projects. These are typically corrosion-resistant, durable, and secure. The deep threads you will find here prevent stripping and provides a good hold.
Recommendation – Erioctry M3 Stainless Steel Wood Screw
M4 screw diameter
The M4 size is common among assembling wood pieces, such as:
- and furniture.
We recommend drilling a small hole before tapping.
The following are the frequently asked questions about wood screw sizes.
The most common size is Gauge #8.
The first number refers to the diameter in inches, while the second refers to the threads per inch (TPI).
Gauge #10 is bigger than gauge #8. A higher number denotes a larger screw.
In most cases, the head does not include the length measurement.