Lag Screws
Lag screws are heavy wood screws with a hex head and a gimlet point. They are driven into a pilot hole in wood; they are not machine bolts.
Lag screw basics
| Diameters | 1/4 to 1-1/4 in typical |
|---|---|
| Material | Usually low-carbon steel, plain, zinc or hot-dip galvanized |
| Length | Under the head to the tip of the point |
| Pilot hole | Sized to wood species and diameter per NDS or maker chart |
These tables carry the same figures as the printed sheet below.
The printed sheet
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Text version of this sheet
ASME B18.2.1 · hex lag screws
What it is
FIELD IDENTIFICATION
Lag screws are heavy wood screws with a hex head and a gimlet point. They are driven into a pilot
hole in wood; they are not machine bolts.
Hex head, coarse wood thread, gimlet point
Lag screw basics
Diameters
1/4 to 1-1/4 in typical
Material
Usually low-carbon steel, plain, zinc or hot-dip galvanized
Length
Under the head to the tip of the point
Pilot hole
Sized to wood species and diameter per NDS or maker chart
Key points
Use hot-dip galvanized or stainless in pressure-treated lumber; zinc plate corrodes quickly there.
Lag screws usually carry no grade mark.
Governing standards: ASME B18.2.1-2012 (R2021); AWC NDS (wood connections). Editions shown are the latest confirmed as of September 2026. The drawing and the governing
standard always take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-E43A03 · thefastenerapp.com/fastener-guide/technical-reference/lag-screws · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
