Wood species
Limba wood
Limba is a hardwood (Terminalia superba). At 12% moisture content it has a Janka hardness of 490 lbf (2,180 N) and it weighs about 28 lb/ft³ (455 kg/m³), 2.4 lb (1.07 kg) per board foot.
Also called: afara.
Key numbers
- Janka hardness, 12% MC
- 490 lbf (2,180 N)
- Green: 400 lbf (1,779 N)
- Weight at 12% MC
- 28 lb/ft³ (455 kg/m³)
- 2.4 lb per board foot
- Specific gravity (oven-dry weight)
- 0.38 on green volume
- Shrinkage, green to oven-dry
- 6.2% tangential
- Radial 4.5%, volumetric 10.8%
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4)
Why: From the USDA Wood Handbook, which collected these values from the world literature; limba's density is worked from its specific gravity with the Handbook's own equations.
How much limba moves
A 12 in wide flatsawn board of limba that goes from 6% to 12% moisture content swells about 0.16 in (about 5/32 in, 4 mm). Quartersawn, the same board moves about 0.11 in (about 1/8 in, 2.8 mm). Flatsawn faces move 1.4 times as much as quartersawn ones, because the wood shrinks 6.2% around the growth rings but only 4.5% across them.
Worked from the Wood Handbook's shrinkage values (Table 4-4) with its Eq. 13-4; the Handbook gives no movement coefficients for imported woods. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Gray-white to creamy or yellow-brown, sometimes with nearly black streaks that give a figure prized for veneer.
- Grain and texture
- Generally straight, uniform but coarse texture.
- Working and character
- Easy to dry, with fairly low shrinkage reported; easy to work and to cut into veneer. Not resistant to decay or insects.
- Uses
- Plywood, furniture, interior joinery and sliced decorative veneer.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-28.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for limba from Wood Handbook Table 5-5b (p. 5-23), which the Handbook says were collected from the world literature, on clear, straight-grained specimens. Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 6,000 psi (41 MPa) | 8,800 psi (61 MPa) |
| Stiffness (MOE) | 770,000 psi (5.3 GPa) | 1,010,000 psi (7 GPa) |
| Crushing strength (compression parallel to grain) | 2,780 psi (19 MPa) | 4,730 psi (33 MPa) |
| Shear parallel to grain | 880 psi (6 MPa) | 1,410 psi (10 MPa) |
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.
- Germany's federal list of sensitizing substances (TRGS 907) names Terminalia superba as a sensitizer of the airways.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The Wood Handbook prints 490 lbf of side hardness at 12% moisture content for limba, a value it says was collected from the world literature (Table 5-5b, p. 5-23).
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4) , 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, collected from the world literature (its Tables 5-5 and 4-4) , sources [1]
So
The Handbook gives only the green specific gravity (0.38) for limba, so it is moved to 12% with the volumetric shrinkage of 10.8% (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 28 lb/ft³, or 2.4 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources