Wood species
Bubinga wood
Bubinga is a hardwood (Guibourtia spp.). At 12% moisture content it has a Janka hardness of 2,690 lbf (11,966 N) and it weighs about 54 lb/ft³ (869 kg/m³), 4.5 lb (2.05 kg) per board foot.
Key numbers
- Janka hardness, 12% MC
- 2,690 lbf (11,966 N)
- Weight at 12% MC
- 54 lb/ft³ (869 kg/m³)
- 4.5 lb per board foot
- Specific gravity (oven-dry weight)
- 0.71 on green volume
- Shrinkage, green to oven-dry
- 8.4% tangential
- Radial 5.8%, volumetric 14.2%
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; bubinga's density is worked from its specific gravity with the Handbook's own equations.
How much bubinga moves
A 12 in wide flatsawn board of bubinga that goes from 6% to 12% moisture content swells about 0.22 in (about 7/32 in, 5.5 mm). Quartersawn, the same board moves about 0.15 in (about 5/32 in, 3.7 mm). Flatsawn faces move 1.4 times as much as quartersawn ones, because the wood shrinks 8.4% around the growth rings but only 5.8% 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
- Pink, vivid red or red-brown with purple streaks, turning yellow or medium brown with a reddish tint in air.
- Grain and texture
- Fine to moderately fine texture.
- Working and character
- Moderately hard and heavy but works well with hand and machine tools. Drying can be difficult; with care it dries well.
- Uses
- Turnery, flooring, furniture parts, cabinetwork and decorative veneer.
The Handbook reports that the bubinga species are listed in CITES Appendix II.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-22.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for bubinga from Wood Handbook Table 5-5b (p. 5-22), 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) | — | 22,600 psi (156 MPa) |
| Stiffness (MOE) | — | 2,480,000 psi (17.1 GPa) |
| Crushing strength (compression parallel to grain) | — | 10,500 psi (72 MPa) |
| Shear parallel to grain | — | 3,110 psi (21 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.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The Wood Handbook prints 2,690 lbf of side hardness at 12% moisture content for bubinga, a value it says was collected from the world literature (Table 5-5b, p. 5-22).
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 (0.71) for bubinga, so it is moved to 12% with the volumetric shrinkage of 14.2% (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 54 lb/ft³, or 4.5 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources