Wood Screw
Screws · flat head wood screw · countersunk wood screw
Definition: A wood screw has coarse, deep threads that cut into wood and a tapered shank that draws the screw tight. Most have a flat, countersunk head.
Anatomy
■ Head■ Shank■ Threads■ Point
Governing standards: ASME B18.6.1
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| #6 x 1 | M3.5 x 25 | 1/4 | 3/32 |
| #8 x 1-1/2 | M4 x 40 | 5/16 | 7/64 |
| #10 x 2 | M5 x 50 | 3/8 | 1/8 |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Standard | low carbon steel | — | None |
| Hardened | case-hardened steel | — | None |
Pilot Hole Sizes
| Screw size | Softwood pilot | Hardwood pilot |
|---|---|---|
| #6 | 3/64 | 1/16 |
| #8 | 7/64 | 1/8 |
| #10 | 1/8 | 9/64 |
Drill the pilot hole to roughly the screw root diameter. Always test on scrap.
Materials
- Zinc-plated steel
- Stainless steel
- Brass
- Silicon bronze
- Coated (deck) screws
Pros & Cons
Pros
- Strong hold in wood without a nut
- Countersunk head sits flush
- Inexpensive and widely available
Cons
- Can split hardwoods without a pilot hole
- Lower pull-out strength than a lag screw
- Plain steel rusts outdoors
Typical Uses
- General woodworking
- Cabinetry and furniture
- Trim and finish carpentry
- Decking (with coated/deck screws)
Alternatives & Related
- Deck Screw — Corrosion-coated with a self-countersinking head for outdoor decks
- Lag Bolt — Much higher strength for heavy structural connections
Top Picks
- Wood screw assortment — #4–#10, flat head
Where to Buy
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FAQ
What size pilot hole for a #8 wood screw?
About 7/64 in. in softwood and 1/8 in. in hardwood for the shank section. Pre-drilling prevents splitting, especially near board ends.
Wood screw vs drywall screw?
Wood screws have deeper, sharper threads and no phosphate coating; drywall screws are brittle and snap under lateral load. Use wood screws for wood.