Wood species
Azobe wood
Azobe is a hardwood (Lophira alata). At 12% moisture content it has a Janka hardness of 3,350 lbf (14,902 N) and it weighs about 68 lb/ft³ (1,085 kg/m³), 5.6 lb (2.56 kg) per board foot.
Also called: ekki.
Key numbers
- Janka hardness, 12% MC
- 3,350 lbf (14,902 N)
- Green: 2,890 lbf (12,855 N)
- Weight at 12% MC
- 68 lb/ft³ (1,085 kg/m³)
- 5.6 lb per board foot
- Specific gravity (oven-dry weight)
- 0.87 on green volume
- Shrinkage, green to oven-dry
- 11.0% tangential
- Radial 8.4%, volumetric 17.0%
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; azobe's density is worked from its specific gravity with the Handbook's own equations.
How much azobe moves
A 12 in wide flatsawn board of azobe that goes from 6% to 12% moisture content swells about 0.29 in (about 9/32 in, 7.4 mm). Quartersawn, the same board moves about 0.22 in (about 7/32 in, 5.5 mm). Flatsawn faces move 1.3 times as much as quartersawn ones, because the wood shrinks 11.0% around the growth rings but only 8.4% 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
- Dark red, chocolate brown or purple-brown, with white deposits in the pores.
- Grain and texture
- Coarse texture, usually interlocked grain.
- Working and character
- Strong and very heavy. Very hard to work and it blunts tools badly when dry, though it dresses smooth and usually glues well. Very difficult to dry; very durable against decay.
- Uses
- Heavy construction, harbor work, heavy-duty flooring and railroad ties.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-21.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for azobe 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) | 16,900 psi (117 MPa) | 24,500 psi (169 MPa) |
| Stiffness (MOE) | 2,160,000 psi (14.9 GPa) | 2,470,000 psi (17 GPa) |
| Crushing strength (compression parallel to grain) | 9,520 psi (66 MPa) | 12,600 psi (87 MPa) |
| Shear parallel to grain | 2,040 psi (14 MPa) | 2,960 psi (20 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 3,350 lbf of side hardness at 12% moisture content for azobe, 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 (0.87) for azobe, so it is moved to 12% with the volumetric shrinkage of 17% (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 68 lb/ft³, or 5.6 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources