Wood species
Soft maple wood
Soft maple is a hardwood; this page covers the soft maple group, led by red maple (Acer rubrum). At 12% moisture content it has a Janka hardness of 950 lbf (4,226 N) and it weighs about 38 lb/ft³ (605 kg/m³), 3.1 lb (1.43 kg) per board foot.
Names and species on this page: red maple, silver maple, bigleaf maple.
Key numbers
- Janka hardness, 12% MC
- 950 lbf (4,226 N)
- Green: 700 lbf (3,114 N)
- Weight at 12% MC
- 38 lb/ft³ (605 kg/m³)
- 3.1 lb per board foot
- Specific gravity (oven-dry weight)
- 0.54 at 12% MC volume
- 0.49 on green volume
- Shrinkage, green to oven-dry
- 8.2% tangential
- Radial 4.0%, volumetric 12.6%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; soft maple's density is worked from its specific gravity with the Handbook's own equation.
How much soft maple moves
A 12 in wide flatsawn board of red maple that goes from 6% to 12% moisture content swells about 0.21 in (about 7/32 in, 5.3 mm). Quartersawn, the same board moves about 0.1 in (about 3/32 in, 2.5 mm). Flatsawn faces move 2.1 times as much as quartersawn ones, because the wood shrinks 8.2% around the growth rings but only 4.0% across them.
Worked with the Wood Handbook's dimensional change coefficients for red maple (Table 13-5: 0.00289 tangential, 0.00137 radial per 1% change in moisture content), which hold between 6% and 14%. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Heartwood and sapwood look like hard maple; the sapwood is somewhat lighter than the heartwood.
- Grain and texture
- Fine and even, like hard maple.
- Working and character
- Resembles hard maple but is not as heavy, hard or strong.
- Uses
- Furniture, veneer, wooden ware, boxes, pallets and crossties.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-8 to 2-9.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of red maple tested by the Forest Products Laboratory (Wood Handbook Table 5-3b). Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 7,700 psi (53 MPa) | 13,400 psi (92 MPa) |
| Stiffness (MOE) | 1,390,000 psi (9.6 GPa) | 1,640,000 psi (11.3 GPa) |
| Crushing strength (compression parallel to grain) | 3,280 psi (23 MPa) | 6,540 psi (45 MPa) |
| Compression perpendicular to grain | 400 psi (3 MPa) | 1,000 psi (7 MPa) |
| Shear parallel to grain | 1,150 psi (8 MPa) | 1,850 psi (13 MPa) |
| Tension perpendicular to grain | — | — |
A dash means the Handbook prints no value; none is filled in.
The soft maple group
The Handbook tests each species separately; they are sold together as soft maple. Across the 3 species measured, Janka hardness at 12% runs from 700 to 950 lbf.
| Species | Janka, 12% MC | Weight, 12% MC | Tangential shrinkage |
|---|---|---|---|
| Red mapleAcer rubrum | 950 lbf | 38 lb/ft³ | 8.2% |
| Silver mapleAcer saccharinum | 700 lbf | 33 lb/ft³ | 7.2% |
| Bigleaf mapleAcer macrophyllum | 850 lbf | 34 lb/ft³ | 7.1% |
Dust and health
- Wood dust is classed as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer, chiefly for cancers of the nose and sinuses.
- NIOSH recommends keeping wood dust exposure to 1 mg/m³ of total dust, as quoted in OSHA's sawmill guidance.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The USDA Forest Products Laboratory measured red maple at 950 lbf of side hardness at 12% moisture content, on clear, straight-grained samples (Wood Handbook Table 5-3b).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , sources [1]
What that means
Side hardness (Janka) is the load needed to press a 0.444 in (11.28 mm) steel ball halfway into the wood across the grain; a higher number dents less (Handbook p. 5-5).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , sources [1]
So
Density at 12% is water's density × specific gravity × (1 + 0.12) (Handbook Eq. 4-14): 62.43 × 0.54 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 38 lb/ft³, or 3.1 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources