Square Lag Screw

Square lag screws come with a rustic look. They are used often in wood construction and sometimes for aesthetic purposes too. Square leg screws are generally available in the marketplace as a standard stock product.


Baseline Bolts manufactures top quality square lag screws. With a diameter of 1/2″ – 1-1/2″, these bolts fulfill most specifications of the ASTM, SAE and AASHTO. In fact, we can even create special tooling to help produce nonstandard bolt heads / head dimensions with the client’s preferred logo and/or name.
When there are no specifications given, non-standard lag screws manufactured by BBI generally have a semi-cone point rather than a cone point or a gimlet. It’s crucial to sport a full point as a pilot hole that’s as large as the root diameter of the lag screw needs to be drilled prior to installation. Moreover, in small diameter screws, to facilitate installation without a pilot hole, a gimlet point is designed. Lag screws in the above mentioned diameters generally do not demand a gimlet point because much torque is needed to install large screws if it’s not chosen to drill a pilot hole first. If a pilot hole is absent, the heads of screws often break before installation of the lag screw.

Standard Thread Length

The minimum thread length for square lag screws shall be equal to half the nominal screw length plus 1/2″ or 6″, whichever is less. One should consider longer than standard thread lengths for lag screws which are extremely long.

Square Lag Dimensions