Lag & Coach Screws — Complete Size Reference
Complete reference for metric lag screws (coach screws) from M6 to M12. Wrench sizes, pilot drill sizes, and applications for wood construction.
About lag screws
Lag screws (also called coach screws) have a hexagonal head and wood screw thread. They are designed for heavy-duty wood-to-wood connections.
Common applications
- Timber framing
- Deck construction
- Structural wood connections
- Heavy wood fixtures
Installation tips
- Always drill a pilot hole to prevent splitting
- Pilot hole should be slightly smaller than core diameter
- Use washers under the head for better load distribution
- Do not over-torque — wood can strip