Wood species
African mahogany wood
African mahogany is a hardwood (Khaya spp.). At 12% moisture content it has a Janka hardness of 830 lbf (3,692 N) and it weighs about 31 lb/ft³ (497 kg/m³), 2.6 lb (1.17 kg) per board foot.
Also called: khaya.
Key numbers
- Janka hardness, 12% MC
- 830 lbf (3,692 N)
- Green: 640 lbf (2,847 N)
- Weight at 12% MC
- 31 lb/ft³ (497 kg/m³)
- 2.6 lb per board foot
- Specific gravity (oven-dry weight)
- 0.42 on green volume
- Shrinkage, green to oven-dry
- 4.5% tangential
- Radial 2.5%, volumetric 8.8%
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; African mahogany's density is worked from its specific gravity with the Handbook's own equations.
How much African mahogany moves
A 12 in wide flatsawn board of african mahogany that goes from 6% to 12% moisture content swells about 0.11 in (about 1/8 in, 2.8 mm). Quartersawn, the same board moves about 0.06 in (about 1/16 in, 1.6 mm). Flatsawn faces move 1.8 times as much as quartersawn ones, because the wood shrinks 4.5% around the growth rings but only 2.5% 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
- Pale pink to dark reddish brown.
- Grain and texture
- Frequently interlocked grain; medium to coarse texture like American mahogany.
- Working and character
- Easy to dry, variable to machine, nails and glues well and finishes very well. Moderately durable, less so than American mahogany.
- Uses
- Furniture, cabinetwork, interior woodwork, boats and veneer.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-29.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for african mahogany 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) | 7,400 psi (51 MPa) | 10,700 psi (74 MPa) |
| Stiffness (MOE) | 1,150,000 psi (7.9 GPa) | 1,400,000 psi (9.7 GPa) |
| Crushing strength (compression parallel to grain) | 3,730 psi (26 MPa) | 6,460 psi (45 MPa) |
| Shear parallel to grain | 931 psi (6 MPa) | 1,500 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 TRGS 907 lists one African mahogany species, Khaya anthotheca, as a skin sensitizer; the Handbook’s figures cover the Khaya genus.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The Wood Handbook prints 830 lbf of side hardness at 12% moisture content for african mahogany, 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 (0.42) for african mahogany, so it is moved to 12% with the volumetric shrinkage of 8.8% (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 31 lb/ft³, or 2.6 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources