Wood species
Tanoak wood
Tanoak is a hardwood (Lithocarpus densiflorus). It weighs about 45 lb/ft³ (725 kg/m³), 3.8 lb (1.71 kg) per board foot.
Also called: tanbark-oak.
Key numbers
- Janka hardness, 12% MC
- Not measured
- Weight at 12% MC
- 45 lb/ft³ (725 kg/m³)
- 3.8 lb per board foot
- Specific gravity (oven-dry weight)
- 0.58 on green volume
- Shrinkage, green to oven-dry
- 11.7% tangential
- Radial 4.9%, volumetric 17.3%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; tanoak's density is worked from its specific gravity with the Handbook's own equation.
How much tanoak moves
A 12 in wide flatsawn board of tanoak that goes from 6% to 12% moisture content swells about 0.3 in (about 5/16 in, 7.7 mm). Quartersawn, the same board moves about 0.12 in (about 1/8 in, 3.1 mm). Flatsawn faces move 2.4 times as much as quartersawn ones, because the wood shrinks 11.7% around the growth rings but only 4.9% across them.
Worked with the Wood Handbook's dimensional change coefficients for tanoak (Table 13-5: 0.00423 tangential, 0.00169 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
- Light reddish-brown sapwood that darkens with age to match the dark reddish-brown heartwood.
- Grain and texture
- Straight.
- Working and character
- Heavy and hard, with strength close to eastern white oak except in compression across the grain. It shrinks more than white oak, can collapse while drying, and decays easily, but it machines and glues well and takes stain readily.
- Uses
- Flooring (it is hard and wear resistant), truck flooring, furniture and veneer.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-10.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of tanoak 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) | 10,500 psi (72 MPa) | — |
| Stiffness (MOE) | 1,550,000 psi (10.7 GPa) | — |
| Crushing strength (compression parallel to grain) | 4,650 psi (32 MPa) | — |
| Compression perpendicular to grain | — | — |
| Shear parallel to grain | — | — |
| Tension perpendicular to grain | — | — |
A dash means the Handbook prints no value; none is filled in.
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 Wood Handbook prints no side hardness for tanoak (Table 5-3b shows "—"), so none is given here.
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
The Handbook gives only the green specific gravity (0.58) for tanoak, so it is moved to 12% with the volumetric shrinkage of 17.3% (Eqs. 4-9 and 4-11), then multiplied by water's density and 1.12 (Eq. 4-14).
Arithmetic: exact by definition , sources [1]
The number
About 45 lb/ft³, or 3.8 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources