Lag Screws

Hex Lag Screws

 

Hex lag screws, also called lag bolts, are used in wood construction. The threads on lag bolts are designed to embed into the wood, rather than relying on a nut to secure the connection. A pilot hole is typically pre-drilled in the wood before inserting the bolt, and must be sized to allow the threads to embed tightly and securely in the wood. Square lag screws are also available and are used for aesthetic purposes to provide a rustic look.

Dimensions

Bolt Diameter E F H Threads Per Inch Thread Dimension
Body Diameter Width Across Flats Head Height
Max Min Pitch
Flat At Root Depth of Thread Root Diameter
1/4 0.260 0.237 7/16 11/64 10 0.100 0.043 0.173
5/16 0.324 0.298 1/2 7/32 9 0.100 0.043 0.039 0.173
3/8 0.388 0.360 9/16 1/4 7 0.143 0.062 0.055 0.265
1/2 0.515 0.482 3/4 11/32 6 0.167 0.072 0.064 0.371
5/8 0.642 0.605 15/16 27/64 5 0.200 0.086 0.077 0.471
3/4 0.768 0.729 1-1/8 1/2 4-1/2 0.222 0.096 0.085 0.579
7/8 0.895 0.852 1-5/16 37/64 4 0.250 0.108 0.096 0.683
1 1.022 0.976 1-1/2 43/64 3-1/2 0.286 0.123 0.110 0.780
1-1/8 1.149 1.098 1-11/16 3/4 3-1/4 0.308 0.133 0.119 0.887
1-1/4 1.277 1.223 1-7/8 27/32 3-1/4 0.308 0.133 0.119 1.012
1-3/8 1.404 1.346 2-1/16 29/32 3 0.333 0.143 0.128 1.119
1-1/2 1.531 1.469 2-1/4 1 3 0.333 0.143 0.128 1.244

Dimensions per ASME B18.2.1 1996

 

Tolerance on Length Nominal Screw Size Nominal Screw Length
Thru 6 in. Over 6 in.
1/2 and smaller +-0.12 +-0.25
Over 1/2 +-0.25 +-0.25
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