What are lag bolts?

Lag bolts, also known as lag screws are large wood screws that have heads in the shape of a hexagon and are known to be some of the toughest fasteners. The head of a lag bolt is typically an external hex.

Though these fasteners are actually screws, because of their large square or hexagonal heads they have remained in the minds of tradesmen as bolts.

They are extremely sturdy fasteners and are generally used for connecting heavy lumber or other heavy materials that bear an intense load.

These Lag Bolts are really massive in size and can range in diameter from ¼ inch to 1 ¼ inch and a minimum of 1/4 inch to 6 inches in length and are different from the normal wood, sheet metal or self drilling screws.

The materials are commonly carbon steel substrate with a galvanized zinc coating for corrosion resistance. This coating can either be bright (electroplated), yellow (electroplated) or dull gray (hot dip galvanized)

What are lag bolts used for?

Since lag bolts are some of the toughest types of screws they are mostly used for connective heavy lumber and also other materials that are intense load bearing.

These bolts are used to lag lumber framing together, to lag machinery feet to wood floors and also for other carpentry applications that are heavy duty. Early on they were principally used for fastening of lags such as barrel staves and other such similar parts and thus the name ‘lag’.

How are lag bolts different from the others?

Lag bolts are different from other common ones like the wood screws, sheet metal screwy and self drilling screws; each of them have their own purpose and use though some of them overlap.

To quote an example, wood screws are used for connecting wood to wood and they are coarsely threaded but do not go all the way up. These are different from Lag Bolts or screws since they thread their way through the wood while they are being screwed in, but when it comes to lag screws they require a hole to be drilled first.

Lag screws require a nut on one side for holding things together; wood screw does away with the need for a nut due to the tight fit of the wood screw.

Wood screws are generally smaller than lag screws and do not use nuts and they cannot bear the load that lag bolts are able to.

And both the wood screws and the lag screws are different from sheet metal screws which have threads all along the shaft. These sheet metal screws are required every time you need to screw through metal even if it is for attaching metal to wood. More information on the different types of popular lagbolts.

Wood screws, sheet metal screws and self-tapping screws are available with different types of heads, lag bolts are available only with hex heads. And to drive in a screw that has a hex head one would need to use a nut driver or ratchet; when a lot of torque is needed it is the hex heads that are used.