Why Do Wood Screws Have A Shank?

It’s time to start your next wood working project. Grab your tools from the garage, find a box of screws, and wood, cut and ready to be installed. You start driving your first screw and boom, it stops and snaps. You try again, same thing. Then you realize you are using sheet metal screws, not wood screws! One quick trip to AlbanyCountyFasteners.com offers a quick fastener fix and your package shows up in the mail few days later filled with deck screws and wood screws. Hastily, you grab the package in excitement and run out to your shop to continue your work. Open the box and wait, what’s that? Why do these screws have an un-threaded portion? That can’t be right…Why would you want that?

It is one of the most misunderstood designs in the industry. Why is there a shank (shoulder) on a wood screw? If a wood screw was threaded all the way up, it would overheat and snap. Before we can explain why this happens, let’s start with the basics.

What Is A Wood Screw?

A wood screw is a screw made up of a head, shank and threaded body. Since the entire screw is not threaded, it is common to call these screws partially threaded (PT).

Head	The head of a screw is the portion that contains the drive and is considered the top of the screw. Most wood screws are Flat heads. Other common heads: Oval, Round, Hex, Modified Truss, Trim Flat.
Shank	The shank is the smooth portion of a wood screw which has no threads and begins immediately beneath the head.
Threaded Portion	The threads start just below the shank and extend all the way to the tip of the screw.

Now that we know what the different sections of a screw are, we can begin to understand what exactly happens during screw installation.

The unthreaded shank of a screw has dual purposes.

The First Purpose

First, when a screw that is fully threaded is driven into wood, this screw can connect two pieces of material together but it will not pull the two pieces against each other; once the head reaches the material, the screw will stop spinning.

Having an unthreaded shank at the top allows the tip of a wood screw to pull the screw into the wood just as a regular screw would. The difference is that the shoulder portion of the screw will actually slide through the first layer of wood and pull it against the head. This causes compression from the head to the threads. When installing two pieces of wood together then the first will be pulled tightly against the second one. The threads can continue to pull forward as long as enough torque is applied. Coincidentally, this can also make the removal process much easier than trying to remove a fully threaded screw.

*Note: This process of continuing to tighten after a wood screw reaches the head and snug wood together is known as over-tightening and may cause damage as the head is pulled to forcefully into the wood.

The Second Purpose

Second, when a fully threaded screw is being screwed into wood the screw threads cause friction. This friction results in the screw heating up. This causes two flaws in the material. As the metal heats up it will begin to expand. Once it expands inside of a hole that was drilled for a specific sized screw, the screw will seize in the hole. At the same time, the materials overall strength has now also been compromised due to the heat. Overheating leads to a screw breaking and snapping.

These two factors will highlight any flaws the screw may have and exploit them. This typically results in bending or snapping of the screw. So, how can a shank help? The shank allows for heat dispersion in a screw. As the threads begin creating heat, it moves up into the shank which will take longer to heat up and will not generate nearly the same amount of friction when it goes through the wood.

This unthreaded shoulder will minimize the amount of heat a screw generates upon install thus keeping it from expanding in size and compromising the materials strength.

Conclusion

To conclude, the shank of a wood screw is used to tightly compress two pieces of wood against each other and minimize the heating up of the screw caused by friction. This results in a strong firm hold between two wooden materials with little effort, and just as importantly, no broken screws.

Other information

Looking for more information about screws? Check out our Screws blog post to learn about many different types of screws.

We also recommend using lubrication when installing wood screws into very hard wood. A DIY option that is available is simply adding soap to the fastener. Soap acts as a natural lubricant but it should be noted that many soaps have glycerin in them which can actually attract moisture. This can result in fasteners deteriorating faster than expected.

A full blown solution is to use MRO Anti-Seize Solution. Not only will this lubricate your nails before installation but it can also add a protective coating to deter from corrosion!

Finishing Cup Washers Install

Create A Clean Look With Finish Washers

Finishing cup washers are indented washers used with either oval or flat head screws. These washers are designed to create a flush finish, often seen on furniture.

Installing Finishing Cup Washers

The installation of these washers is very simple. There are two basic types of these washers. The photo on the left shows a standard black oxide cup washer and the photo on the right shows a stainless steel cup washer with a flange around the outside.

finishing cup washers stainless steel finish cup washers

Installation

When installing these washers it is important to only snug them. These washers do not sit perfectly upon the installation material and over-tightening them will begin to distort their shape.

brass cup washers installing finishing cup washers

The Finished Product

Once installed you can see that finish cup washers create a very clean look around a screw head making it appear to be intentionally exposed, instead of just sticking out.

installed finishing cup washers

Albany County Fasteners carries a variety of these washers in many different materials to help you find the right tool for the job. Check out Finishing Cup Washers page to see our selection of cup washers.

Installing Wedge Anchors

Installing Wedge Anchors in Concrete

Wedge anchors are fasteners designed for use in masonry materials (most commonly concrete) and used to secure materials and equipment. Concrete wedge anchors are designed to go into a pre-drilled hole and expand, creating a grip so they cannot be “pulled out” or removed. Today we will be reviewing the proper installation of a post base into a concrete floor.

What will you need?

Before we begin let’s make sure we have the proper tools for the job.

Step One

The first thing you need to do when installing a wedge anchor is choose the proper anchor material. Wedge anchors come in many materials and all serve different purposes. Stainless steel and hot dip galvanized are two very popular wedge anchor materials, but the correct material varies by application. Not sure what material you need? Check out our Material Guide to learn about all the different materials available.

wedge anchors

Step Two

Once you’ve chosen a material, its time to get your drill ready. When installing a wedge anchor, it’s important to have a minimum of 2-1/2 inches embedded into the concrete. There should also be at least an inch exposed, enough for the attaching material to grab onto. To measure ours, we placed the wedge anchor about an inch below the tip of the SDS drill bit and then used blue painters tape to mark off the drill where we should stop drilling. Marking the stop point with blue tape will allow you to drill consistent holes and prevent you from over/under drilling.

Step Three

drilling into concrete

Now that we’ve applied our drill bit with tape, its time to begin the drilling. BUT NOT SO FAST. First we need to put on our safety goggles and gloves, always wear safety gear when cutting. Now that you are safe and ready to work, simply apply pressure to the place you want to drill and let the bit begin to do its work. Once your drill bit reaches the blue painters tape, you will know that the hole has reached the necessary depth and you can stop drilling.

Step Four

hammering in wedge anchors Carefully brush away any of the debris from drilling to clear the hole and begin installation of the anchor. The next step is to insert the masonry anchor into the hole. It should be a very tight fit and will need to be hammered into place. The end result should leave about an inch (or more depending on how much room you need) above the surface to allow for anchoring.

wedge anchor ready for post base

Now that the anchor is installed we can apply the post base, square washer, and nut to the wedge anchor. After placing them on, you screw the nut onto the wedge anchor creating a strong, sturdy anchoring station. Now that you’ve completed the installation, take a step back and admire your handiwork. This post base is now ready for the next step in your building project.

ratcheting on postbase Anchored postbase

Lock Nuts and Lock Washers

Locking Fasteners

Locking fasteners come in many varieties and styles to help keep your fastener assemblies secure and resist loosen from vibration. Locking nuts and washers are great tools to keep assemblies from accidental loosening, basically they stop things from falling apart! But what kind of locking nut or washer should you buy? Below we explain some of the popular types to help you choose.

Lock Washers

Lock washers are washers with designed changes to add extra friction or tension to your fastener assembly to prevent loosening. Each lock washer is engineered to work for different applications, if you are unsure if the hardware you are selecting is appropriate, make sure to consult an engineer.

Click the name of any type of lock washer or nut you would like to know more about or buy directly from our website.

Lock Washer Type	Description	Image
External Tooth “External Star”	External tooth lock washers are serrated and create tension between the teeth and the installation surface. This increased tension can make it harder for a fastener assembly to vibrate loose.
Internal Tooth “Internal Star”	Internal tooth lock washers have bent teeth that are designed to create tension and friction on the inside of a bolt head or against the nut. They are often chosen over external tooth lock washers due to their cleaner finish.
High Collar Split Ring	High collar lock washers are similar to regular split ring washers except they are made to fit under the head of a socket cap screw. They have a smaller outer diameter designed to fit into a counter-bored hole.
Split Ring	Split ring lock washers are washers with a cut in them and bent into a helicoil shape. As the nut loosens, extra pressure is applied from the expanding lock washer which can stop a bolt from loosening unintentionally

Lock Nuts

Lock nuts are nuts that have been altered in some way to deter them from vibrating loose. Below are a few of the more common types of lock nuts you are likely to come across.

Lock Nut Type	Description	Image
Castle	Castle nuts, while not technically lock nuts, can function as lock nuts after installation. They require that a cotter pin be placed through a hole in a bolt and through the crown of the nut. We consider these to be lock nuts because the cotter pin will hold the nut in place if it comes loose.
Flange Serrated	Flange serrated nuts have one wide side that acts as an integrated washer. The washer side has serrations which, when tightened, can help prevent loosening by adding extra friction to the assembly.
Keps-K	Keps K lock nuts Have an attached spinning washer with teeth that can dig into the assembly. They are similar to that of an external tooth lock washer combined with a nut.
Nylon Insert	Nylon insert lock nuts are a taller nut with the same nylon insert. Threads cut into the insert as installed resulting in a better grip to help prevent a fastener assembly vibrate loose.
Nylon Jam “Thin”	Nylon Jam lock nuts are a low profile nut that have an internal nylon insert. As the bolt is screwed on the threads cut into the nylon holding them in place and preventing vibrations from loosening them.
“Stover” Cone Prevailing Torque	Stover lock nuts have chamfered corners. The distortion in the top threads from the shape of the bolt create resistance to loosening. This is a better choice for high heat applications because no nylon insert is used.
Two Way Reversible	Two way reversible lock nuts have indents on the outside flats of the nut causing distortions of the internal threading. These distortions create resistance of the mating part.

NOTE: We also offer thread locker solutions that can provide a low, medium or high level grip to prevent assemblies from loosening as well.

Fastener Acronyms

Fastener Acronyms can be confusing but they are a constant in the fastener world. At Albany County Fasteners we want to make your experience as simple as possible. To help you better find what you need, we have compiled a list of commonly used acronyms, what they stand for and what they mean.

Machine screws are mostly available in smaller sizes, these screws have a flat point and can be driven into a pre-tapped hole or used with a nut.UNJC+UNJFComparable to UNC and UNFSimilar to UNC and UNF in both external and internal threading. External threading on these have a much larger root radius. These larger roots lead to increased tensile stress and as a result, make them stronger. Below is a list of most of the fastener acronyms you are likely to come across.

Acronym – Term	Description
AN Aeronautical Standards Group	Precedes the dimensional specifications developed by the Aeronautical Standards Group.
ANSI American National Standard Institute	The American National Standard Institute (founded 1918) was formed to create a national standard for sizing.
ASME American Society of Mechanical Engineers	The American Society of Mechanical Engineers (founded 1881) was created to pursue research, education and improvement of the industry while also placing a strong emphasis on public safety.
ASTM American Society for Testing & Materials	The American Society for Testing & Materials (founded 1898) aims to promote safety and health by sharing information about the reliability of different aspects in the manufacturing industry.
CS Countersink	A drilled hole with a wider rim so that a screw or bolt can sit inside that area and be flush with the surface it is installed into.
DIN Deutsches Institut Für Normung	Din, 1917, is the German institute for standardization. They focus on the technical and scientific creation of technical standards.
En-Standards (CEN) European Committee of Standardization	CEN was created to be a mediator between the European Union and European Free Trade Association. They were to pass resolutions which both parties must adhere to.
FT Fully Threaded	Threading that starts at the tip of the screw and goes all the way to the undercut of the head.
GR Grade	A level of material that describes its composition.
HDG Hot Dip Galvanized	A process that adds a layer of corrosion resistance by dipping fabricated steel into a kettle containing molten zinc.
IFI Industrial Fastener Institute	Founded in 1931, the Industrial Fastener Institute is an association who supports standards for the mechanical fastener industry. They often develop standards when one does not exist until a national standard can be provided.
ISO International Organization for Standardization	The ISO, is a federation of 158 countries from all over the world. Based in Switzerland, they propose, develop and implement new standards and then deliver them to the world.
LF Large Flange	A wider surface area, often with a much greater outer diameter, than the typical surface area. Ex: Large Flange Washers.
MS Military Standards	Standardized objectives created by the U.S. Department of Defense.
Prop 65 California’s Safe Drinking Water and Toxic Enforcement Act	A warning label that protects Californians from chemicals which can cause long-term health defects.
PT Partially Threaded	Threading that starts at the tip of a screw and stops at some point allowing for the screw or bolt to have a shoulder.
REACH Authorization and Restriction of Chemicals	A European regulation created to test and determine if chemicals are safe and can be used.
RoHS Restriction of certain Hazardous Substances	RoHS is a directive to restrict hazardous substances in electrical and electronic equipment. Any fastener that is a component of electrical parts and placed on the European Union market must adhere to this restriction.
SAE Society of Automotive Engineers	A society, founded in 1905, to test and create standards for the automotive industry. They also develop standards for heavy-duty and aerospace vehicles.
SD Self Driller or Self Drilling Screws	Primarily used to drill into steel and join materials such as sheet metal today.
SEMS Pre-assembled Screws	Pre-made screw and washer assemblies.
SLT Slotted	A common drive style which is also commonly called a flat head.
SMS Sheet Metal Screws	Sharp threaded screws used to cut into soft metals, wood or plastics.
UN Thread Sizing	A series of threading for applications where UNC, UNF, UNEF and UNS are not applicable.
UNEF Unified National Extra Fine	Threads even smaller than fine threading these extra fine threads are commonly used on very small screws to make the screw stronger.
UNC Unified National Coarse	Coarse threading that is the prefered thread for general use.
UNF Unified National Fine	Fine threading that is not as strong as coarse threading. They do offer finer adjustments than coarse threads.
UNR Unified Round	The root radius must be rounded but does not necessarily have to be inspected.
UNS Unified Special	Threads that are tip(threads per inch) specified but are limited to a specific diameter.

There are many fastener abbreviations, not all of which are listed here. Please let us know in the comments below which acronyms we forgot and help us to create a more informed fastener community!