> Square Lag Screw

Square Lag Screw

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Square lag screws feature a distinctive rustic appearance and are widely used in wood construction, as well as for decorative and aesthetic applications. Square lag screws are generally available in the marketplace as a standard stock product.

Manufacturing

EBB manufactures top-quality square lag screws in diameters ranging from 1/2″ to 1-1/2″, meeting most ASTM, SAE, and AASHTO specifications. We also offer custom manufacturing through special tooling to produce non-standard bolt heads and head dimensions with the client’s preferred logo and/or company name.

Where no specific point specification is provided, non-standard lag screws manufactured by BBI typically feature a semi-cone point rather than a full cone point or a gimlet point. For proper installation, a pilot hole equal to the root diameter of the lag screw must be drilled prior to installation.

Gimlet points are generally designed for small-diameter screws to allow installation without a pilot hole. Lag screws within the above-mentioned diameters typically do not require a gimlet point, as installing large-diameter screws without a pilot hole requires excessive torque. Without a pilot hole, screw heads often fail before full installation is achieved.

Standard Thread Length

The minimum thread length for square lag screws shall be equal to one-half of the nominal screw length plus 1/2″, or 6″, whichever is less. For exceptionally long lag screws, thread lengths longer than the standard may be specified to ensure proper engagement and performance.

Square Lag Dimensions

Square Lag Dimensions

 
Click table to show drawing
Bolt DiameterDFHThreads Per InchThread Dimension
Body DiameterWidth Across FlatsHead HeightPitchTFTDTR
MaxMinFlat At RootDepth of ThreadRoot Diameter
120.5150.48234113260.1670.0720.0640.371
580.6420.6051516276450.2000.0860.0770.471
340.7680.729118124120.2220.0960.0850.579
780.8950.8521516376440.2500.1080.0960.683
11.0220.97611243643120.2860.1230.1100.780
1181.1491.09811116343140.3080.1330.1190.887
1141.2771.22317827323140.3080.1330.1191.012
1381.4041.3462116293230.3330.1430.1281.119
1121.5311.469214130.3330.1430.1281.244

Dimensions per ASME B18.2.1 1996

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