Hardwoods
Hardwoods are the timbers of broad-leaved trees — a botanical class, not a hardness rating, which is why balsa belongs here at 0.15 g/cm³ alongside hard maple at 0.70. The commercial species run 0.55–0.75 g/cm³, with a Janka hardness of 4–6.5 kN, a bending modulus of 10–13 GPa along the grain and a bending strength around 100 MPa, which puts them close to aluminum for stiffness per unit weight. Grain, colour and pore structure differ more than the numbers do, and that — together with movement across the grain — is what usually decides the species.
Popular hardwood grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| White Oak | — | 100 | 0.76 | Good | — | Outdoor, marine and wet-service joinery |
| Hard Maple | — | 108 | 0.7 | Very good | — | Worktops, cutting boards, jigs, wear surfaces |
| Black Walnut | — | 100 | 0.61 | Excellent | — | Dark visible furniture and product parts |
| Ash | — | 110 | 0.67 | Very good | — | Handles, bats and steam-bent parts |
| Beech | — | 110 | 0.72 | Very good | — | Turned parts, tooling and bent work |
| Teak | — | 100 | 0.65 | Good | — | Decks and marine hardware left unfinished |
| Mahogany | — | 90 | 0.55 | Excellent | — | Stable pattern stock, boat joinery, instruments |
Choose hardwood for
Furniture, cabinetry and architectural millwork; worktops, cutting boards and butcher block; tool handles, mallets, bats and bent parts; foundry patterns and jigs; visible prototype and product parts with a warm finish; boat, deck and outdoor joinery in the durable species; flooring, stair parts and anything that is walked on or handled.
Look elsewhere when
The part must stay flat and dimensionally stable across seasons (Plywood, MDF or a polymer), it needs certified repeatable strength (aluminum or steel), it is a wide painted panel (MDF), it will live outdoors without maintenance in a non-durable species (Cedar, Redwood or a composite), it is a crate or framing where a softwood such as Douglas Fir is half the cost, or the tolerance is tighter than about ±0.2 mm.
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Hardwood by application
- Furniture and visible parts
- Black Walnut, White Oak, Oak and Hard Maple depending on colour; Mahogany where stability and a fine finish matter more than hardness. Quarter-sawn stock moves half as much as flat-sawn.
- Worktops and cutting boards
- Hard Maple end-grain or edge-grain, oil-finished; Beech as the European equivalent. Both are closed-grain, food-safe and hard enough not to score.
- Handles, bats and bent parts
- Ash for shock loads and steam bending, Beech and White Oak also bend well; select straight, knot-free grain running the full length of the part.
- Outdoor and marine
- Teak and White Oak without treatment; Mahogany with a maintained finish. Fasten with stainless or silicon bronze — steel stains tannin-rich oak and ash black.
Working with hardwood
- Cutting and machining
- Hardwoods CNC-route and mill cleanly at 18,000–24,000 rpm with sharp up-cut, down-cut or compression tooling and a feed of 0.1–0.3 mm per tooth; ±0.2 mm is routine and ±0.1 mm achievable on small parts from acclimatized stock. Tear-out happens where the cutter exits against the grain and on figured or interlocked grain — climb-cut, use a compression spiral for through cuts, and orient the blank so the grain runs along the longest dimension. Teak dulls tooling with its silica; walnut, mahogany and oak dust need extraction.
- Joining and fastening
- PVA glue makes a joint stronger than the wood if the surfaces are freshly machined and clamped; polyurethane and epoxy for outdoor and oily species, and wipe Teak with solvent before gluing. Pre-drill screws in every hardwood (pilot hole about 90 % of root diameter in oak and maple) and use threaded inserts for repeated assembly. Mortise-and-tenon, dowel and domino joints carry racking loads that screws alone will not.
- Finishing
- Open-pored oak, ash, walnut and mahogany need a grain filler for a glass-smooth gloss; closed-grain maple, beech and birch do not, but they blotch under pigment stain — use a dye or a pre-stain conditioner. Oil and hardwax for touch surfaces, waterborne polyurethane or lacquer for wear, and a film finish on all six faces to keep moisture uptake even. Walnut lightens and cherry darkens in daylight; oak turns black in contact with iron and water.
- Movement and moisture
- Wood moves across the grain by about 0.2–0.3 % per 1 % change in moisture content (tangential) and half that radially, almost nothing along the grain; a 300 mm flat-sawn oak panel changes width by 3–4 mm between a dry winter and a humid summer. Specify 6–8 % moisture content for interior parts and 10–12 % for exterior, acclimatize stock in the shop for a week, and design panels to float in grooves or slot the fixing holes. Quarter-sawn stock and the low-movement species (Teak, Mahogany) are the answer where a solid part must stay true.
Other natural material series
Hardwoods — frequently asked
What is hardwood?
Hardwoods are the timbers of broad-leaved trees — a botanical class, not a hardness rating, which is why balsa belongs here at 0.15 g/cm³ alongside hard maple at 0.70. The commercial species run 0.55–0.75 g/cm³, with a Janka hardness of 4–6.5 kN, a bending modulus of 10–13 GPa along the grain and a bending strength around 100 MPa, which puts them close to aluminum for stiffness per unit weight. Grain, colour and pore structure differ more than the numbers do, and that — together with movement across the grain — is what usually decides the species.
Which grade of hardwood should I use?
White Oak for anything outdoors, wet or structural: closed pores, tannin-rich, rot-resistant and the traditional boat and barrel timber. Hard Maple for worktops, cutting boards, jigs and wear surfaces — the hardest and most abrasion-resistant of the common species and fine-grained enough for crisp CNC detail. Black Walnut for visible furniture and product parts where the dark colour is the point; it is softer than maple and easier to machine. Ash for handles, bats, bent parts and anything that takes shock, and Beech for turned parts, tooling and steam-bent work. Teak for decks and marine hardware that must survive without finish; Mahogany for stable pattern-making stock, boat joinery and instruments; Birch as the lower-cost pale utility hardwood; Balsa only as a core or model material.
Which grade of hardwood is easiest to machine?
Balsa (machinability excellent, 90/100), then Mahogany (90/100).
White oak or red oak?
White Oak for anything wet or outdoors: its pores are plugged with tyloses, so it is watertight and rot-resistant — the timber of barrels, boats and exterior doors. Red oak is more open-pored and cheaper, absorbs water like a straw and grays and rots outside, but it is fine for interior furniture, flooring and cabinetry. They machine and finish the same way; red oak has a pinker cast and coarser figure.
Hard maple or beech for a workbench or cutting board?
Both are dense, closed-grained and food-safe; Hard Maple is a little harder (about 6.4 kN Janka versus 5.8 kN) and paler, Beech is easier to find in Europe, cheaper and bends well. Beech moves more with humidity — around 12 % tangential shrinkage green to dry against 10 % for maple — so a beech top needs more allowance for movement in its fixings. For a top that will be flattened and oiled, either is right; choose by price and colour.