Your Guide to Choosing a Fastener
While there are several factors to consider when selecting a fastener, such as cost, corrosive environment, extreme temperatures, stress, weight load, structural stability, and process applications, two important factors to consider for any application are material and size. The fastener you choose must create a clamping force that prevents the clamped parts from moving and separating. Make the right connection with our huge in-stock selection of anchors and fasteners, numerous locations, and our experienced construction pros.
While referring to penny size and type designations such as “box” or “common” is a typical method for calling out nails, it is more accurate and reduces potential confusion to always call the nail by diameter and length.
Even though wood buildings have repetitive and redundant members, and most connectors are designed to support loads that exceed the service loads placed upon them, the differences can create more deflection and movement as well as increased damage from wind or seismic events. Suddenly, size turns into a safety issue that could have catastrophic results.
Also, non-structural nails, such as nails for components and cladding, should NEVER be used in structural connectors. Screws should ONLY be used if specifically engineered to be used with structural connectors.
How to Select a Fastener
Selecting the right fastener is critical to the success of its application and to your project. Consider these factors when selecting the safest and the best fastener for your project:- Size
- Similar types; do not mix nails and screws in the same connector.
- Application or process
- Corrosion resistance
Size Matters
A common method representing nail sizes is the penny size, which is a length designation. The length of a nail, from the head to the tip of its point, is defined as the “penny.” Size is written with a number and the abbreviation “d” for “denarius” which is Latin for “penny.”While referring to penny size and type designations such as “box” or “common” is a typical method for calling out nails, it is more accurate and reduces potential confusion to always call the nail by diameter and length.
Diameter and Length are Important
The International Building Code® (IBC) evaluates and rates specific fasteners to be installed with specific connectors. But there can be subtle differences between what was specified and what was installed because the diameter and length may not be provided with the fastener type. For example, most hangers use 10d common nails as fasteners, per ICC reports. But installers may not know there are subtle differences in length and diameter between a common 10d nail and a 10d sinker, 10d pneumatic and 10d box nail.Even though wood buildings have repetitive and redundant members, and most connectors are designed to support loads that exceed the service loads placed upon them, the differences can create more deflection and movement as well as increased damage from wind or seismic events. Suddenly, size turns into a safety issue that could have catastrophic results.
Also, non-structural nails, such as nails for components and cladding, should NEVER be used in structural connectors. Screws should ONLY be used if specifically engineered to be used with structural connectors.
Selecting the Right Type
A bolt is a bolt, right? Wrong. Just like we read above that not all nails are the same, the same applies to other fasteners. Take the bolt. A bolt consists of a head, shaft, and threaded end. Once you know what the bolt will be used for, you have to make decisions based on:- Head: hex, screw, socket, or another design? The head design accounts for the amount of torque the bolt will take.
- Shaft length is also based on application.
- Threads: coarse (UNC), fine (UNE) or 8 thread (UN; mostly used in oilfields). Threads have a heavy responsibility; they carry the load. Coarse threads are quicker to assemble, and while fine threads take longer to install because they require more revolutions, they provide a more secure connection with stronger tension.
Common Nail Types
Here are the most common types of nails, usage, and their advantages.
Brads: Common name for nails less than 1 ¼" length with a head larger than the shank, basically a very small finishing nail. Due to its size, brads reduce the possibility of splitting in hardwoods. Easily
Bright: "Smooth finish" nails with a natural, uncoated steel finish. They are often galvanized or hot-dipped with zinc to resist corrosion.
Common: Bright thick shank, regular stock steel, flat round head, and medium diamond point. Shank diameter is larger than box nails of the same penny size. Great for general construction, structural work, and framing due to thickness and sturdy support. Also known as “framing nails.”
Concrete/Masonry - Thick and very strong, hardened steel nails, often with full shaft grooves to help penetrate extremely hard materials by spiraling as driven. Designed to be fastened into concrete, concrete block, and mortar joints.
Duplex head: Specialty fasteners are easy to remove and used in temporary construction (concrete formwork or for attaching temporary roofing cleats). Drive nail until lower head is flush with wood. To tear down, pull nail out using the upper head with hammer claw or pull bar.
Finish/Finishing Nails: Smooth wire nail with a head slightly larger than shank and medium diamond point. Thin enough to not split narrow and thin wood pieces. Can be concealed easily by countersinking below the work surface.
Hot-dipped: A hot tumbling process which coats the nail with a heavy layer of zinc to provide the best corrosion resistance possible and enhance the holding power. For most exposed nailing applications. Meets ASTM A-153 Specifications. Can be used with pressure-treated lumber to prevent corrosion.
Roofing: Also called clout nails. Short smooth or ringed shank for more pull-out resistance and wide flat thin head nail for attaching roofing paper, sheathing, shingles, and sheet metal to wood. Typically have a larger head and heavier gauge. For use in collated nail guns.
Roof Sheathing Rinking Shank Nail: Wire nail with a concentric, full, round head and at least 1 ½” ” shank length deformed with annular rings.
Sinker: Special common nail with a narrow shank and a head designed to be sunk flush with the wood surface. Short, thin and easy to drive with a cement-coated finish.
Collated nails: Strips or coils of nails held together by glue, plastic strips, or paper tape. Designed to be inserted into air-powered nail guns for rapid driving. Available in a variety of nail types.
Box: Coated or galvanized finish, plain shank, regular stock steel, flat round head, and medium diamond point. Shank diameter is smaller than common nails of the same penny size.
Casing: Wire nail with a slightly larger head than a finish nail. Often used for flooring and exterior door frames and trim. Tapered head can be set flush or just below work surface. Often galvanized to resist corrosion.
Connector: Wire nail with a concentric, full, round head and diamond point. The shank can be either deformed with annular rings or smooth.
Post-Frame: Wire nail with a concentric, full, round head and 2 ¼” to 3” deformed shank with annular rings.
Siding: Wire nail with a small shank diameter and a head smaller than other same-size nails; helps conceal the fastener after installation.
Shank Types, Head Styles, Thread Styles, and Point Styles
Self-drilling Screws
A self-drilling screw features a drill point, acting like a drill bit, with sharp cutting threads that will drill a hole and form mating threads at the same time. It’s a type of self-tapping screw, also known as a sheet metal screw, but the two are not interchangeable. The biggest difference between a self-drilling and a self-tapping screws are that self-tapping drives into a pre-drilled hole.
Self-drilling screws are used for quick drilling into metal and wood. The screw is easily recognized by its drill point and notched flute. Acting as a drill bit, the drill point is quicker and easier to install than switching between a drill bit and a driver bit.
Consider these key factors when selecting a self-drilling screw:
- Type and thickness of drilling material. Make sure the drilling material is softer than the screw material. If not, the screw will quickly dull and stop cutting. Determine the thickness of the material being attached so the appropriate fastener length can be selected.
- Drill Flute – An effective drill flute is responsible for clearing debris from a hole as it is being drilled. When a flute is completely embedded, it stops removing chips. When debris builds up in a hole it causes overheating, which can stop drilling.
- Point - Shape of the drilling tip
- Point Length - Determines how deeply the screw can drill
- Pilot - Must be able to completely drill through the material before the threads engage. If the threads engage before drilling is complete, the fastener can bind and break.
- Point Wings - Used on screws to fasten thicker materials, such as wood to metal. Wings drill holes larger than the threads, preventing threads from engaging the wood. When the wings hit steel, they break off, allowing the threads to engage with the steel.
How to Slow or Prevent Fastener Corrosion
Metal, even stainless steel, fasteners can corrode. And, when fasteners corrode, they may lose their carrying ability. It’s important to know why corrosion happens in order to prevent or slow the process, and how to replace corroded fasteners, or if necessary, the surrounding material.The environment where a fastener is installed is key. Ocean salt air, condensation, long-term wetness, fire retardants, fumes, fertilizers, chlorides, sulfates, preservative-treated wood, de-icing salts, construction chemicals, dissimilar metals, soils and more factors can contribute or be a direct cause of corrosion.
Structural engineers and architects should have taken such factors into account when deciding what kind of anchors and fasteners to install.