Wood species
Jatoba wood
Jatoba is a hardwood (Hymenaea courbaril). At 12% moisture content it has a Janka hardness of 2,350 lbf (10,453 N) and it weighs about 54 lb/ft³ (861 kg/m³), 4.5 lb (2.03 kg) per board foot.
Also called: courbaril.
Key numbers
- Janka hardness, 12% MC
- 2,350 lbf (10,453 N)
- Green: 1,970 lbf (8,763 N)
- Weight at 12% MC
- 54 lb/ft³ (861 kg/m³)
- 4.5 lb per board foot
- Specific gravity (oven-dry weight)
- 0.71 on green volume
- Shrinkage, green to oven-dry
- 8.5% tangential
- Radial 4.5%, volumetric 12.7%
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; jatoba's density is worked from its specific gravity with the Handbook's own equations.
How much jatoba moves
A 12 in wide flatsawn board of courbaril that goes from 6% to 12% moisture content swells about 0.22 in (about 7/32 in, 5.6 mm). Quartersawn, the same board moves about 0.11 in (about 1/8 in, 2.8 mm). Flatsawn faces move 1.9 times as much as quartersawn ones, because the wood shrinks 8.5% 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
- Salmon red to orange-brown fresh, drying to russet or reddish brown, often with dark streaks; wide gray-white sapwood.
- Grain and texture
- Medium to rather coarse texture, mostly interlocked grain.
- Working and character
- Hard and heavy, with strength close to shagbark hickory. Moderately difficult to saw and machine and a little hard to plane, but it machines smooth, turns, glues and finishes well, and steam-bends about as well as white oak.
- Uses
- Tool handles, steam-bent parts, flooring, turnery, furniture, cabinetwork and veneer.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-23.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for courbaril 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) | 12,900 psi (89 MPa) | 19,400 psi (134 MPa) |
| Stiffness (MOE) | 1,840,000 psi (12.7 GPa) | 2,160,000 psi (14.9 GPa) |
| Crushing strength (compression parallel to grain) | 5,800 psi (40 MPa) | 9,510 psi (66 MPa) |
| Shear parallel to grain | 1,770 psi (12 MPa) | 2,470 psi (17 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 2,350 lbf of side hardness at 12% moisture content for courbaril, 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 courbaril, so it is moved to 12% with the volumetric shrinkage of 12.7% (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