Nomenclature Debate: Lag Screws or Lag Bolts?

In many trades and industries, there are technical terms for products and processes, and then there are alternate terms more commonly used by the people who work inside of those industries on a daily basis. Fasteners are no different, and one of the nomenclature debates that comes up in fasteners frequently is whether the correct term is lag screws or lag bolts.

Generally, a screw is considered to be defined by its pointed tip and its self-tapping properties, meaning it mates with the substrate by torquing the threads into the surface directly, which holds it into place. These properties are certainly true for lag screws/bolts.

A bolt, in most circumstances, does not mate directly with the substrate but rather mates with a nut to hold an assembly together. Bolts do not have pointed tips and are not self-tapping, they require a nut to complete the holding action.

You may be thinking, if these conditions are true, why is a machine screw or socket screw called a screw and not a bolt? Well, like so many technical names in different industries, terms are applied to items that may not be 100% correct from a technical standpoint, but repeated use of the term by industry insiders makes these names more ubiquitous than their correct descriptions, and this is definitely true in the fastener industry.

So where does that leave us in the lag screw/bolt debate? Technically, the correct terminology is lag screw, but if you use the term lag bolt, no one is going to question what you’re referring to. If you contact Mudge Fasteners at (800) 634-0406, you’re welcome to ask for lag screws or lag bolts, and you’ll still get the exact part you’re looking for.