Lag Bolts vs. Lag Screws: What's the Difference?

Lag bolts, also commonly known as lag screws, are some of the toughest fasteners out there. Used primarily for fastening into heavy lumber, these extremely sturdy fasteners withstand some of the most intense loads. The two terms "lag bolts" and "lag screws" are used interchangeably to refer to the same type of fastener. And for some, this causes plenty of confusion over saying the correct term.

Key Takeaways

• Lag Bolts & Lag Screws can mean the same thing - they have features of both a bolt and a screw, so both terms are used interchangeably.
• Characteristics like diameter, head shape, installation, and uses cause confusion between lag bolts and lag screws, but below we explain in detail the distinctions between them.

Why Do Lag Bolts & Lag Screws Mean the Same Thing?

People use lag bolts or lag screws to say the same thing because these fasteners exhibit characteristics of both a bolt and a screw. Traditionally, bolts are assembled with a nut and have machine threading, while screws are fastened by turning the head and having threads cut into the material. However, due to the design and function of these fasteners, lag bolts (or lag screws) are able to take on traits from both types.

Lag Bolt Characteristics:

• Heavy Diameter: Lag bolts offer strong and durable fastening solutions due to their thick shafts and coarse threads, a feature similar to most bolts. This makes them reliable for heavy-duty applications.
  
  
• Head Shape: Lag bolts predominantly feature hexagonal heads without any slots notched into the top surfaces for screwing. Because of this, lag bolts require fastening from a torque wrench or impact wrench to keep them nice and tight into the material. For more information here, check out our article on the Different Types of Wrenches. However, other head shapes can be found like square head lag bolts or flanged head lag bolts, but these are less common.

• Installation: Lag bolts feature a sharp point familiar with other types of screws but they still usually require a pre-drilled hole, or pilot hole, in order to fasten them properly. Sometimes screws can be considered self-tapping or self-drilling where a pilot hole is not required, but lag bolts are not usually intended for use this way. For more info see our article on Self-Drilling vs. Self-Tapping Screws.

• Use of Washers: While lag bolts do not always require washers, they can be used in certain applications to distribute the load and prevent damage to the material.
• Use of Nuts: Lag bolts are typically designed to be used without nuts because they feature a pointed tip and coarse threads that are meant to be driven directly into wood or other soft materials. The threads bite into the material, providing a strong hold without the need for a nut.

Lag Bolts vs. Lag Screws: Which is Correct?

The terms "lag bolts" and "lag screws" are often used interchangeably in the construction industry, but "lag screws" is technically the more accurate term.

No matter what you call them, or how you use them, lag bolts are easy to install and incredibly reliable for heavy duty materials. Fasteners Plus offers Conquest Lag Bolts made from a variety of high-strength steel options - 316 stainless steel, 304 stainless steel, and hot-dipped galvanized carbon steel - perfect for both interior and exterior applications. Talk with one of our product experts today to learn more about our selection and find the right lag bolts for your needs.

Any Further Questions About Lag Bolts

Our team of experts has a depth of knowledge in the fastener industry. If you have any additional questions, be sure to reach out and we'll be glad to help.

Find it Fast. Get it Fast

If you have any questions about fastener options, please do not hesitate to reach out to our Product Experts at (888) 794-1590 or by email at customerservice@fastenersplus.com.