Wood species
Jelutong wood
Jelutong is a hardwood (Dyera costulata). At 15% moisture content it has a Janka hardness of 390 lbf (1,735 N) and it weighs about 26 lb/ft³ (423 kg/m³), 2.2 lb (1 kg) per board foot.
Key numbers
- Janka hardness, 15% MC
- 390 lbf (1,735 N)
- Green: 330 lbf (1,468 N)
- Weight at 12% MC
- 26 lb/ft³ (423 kg/m³)
- 2.2 lb per board foot
- Specific gravity (oven-dry weight)
- 0.36 on green volume
- Shrinkage, green to oven-dry
- 5.5% tangential
- Radial 2.3%, volumetric 7.8%
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; jelutong's density is worked from its specific gravity with the Handbook's own equations.
How much jelutong moves
A 12 in wide flatsawn board of jelutong that goes from 6% to 12% moisture content swells about 0.14 in (about 1/8 in, 3.5 mm). Quartersawn, the same board moves about 0.06 in (about 1/16 in, 1.4 mm). Flatsawn faces move 2.4 times as much as quartersawn ones, because the wood shrinks 5.5% around the growth rings but only 2.3% 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
- White or straw colored; heartwood and sapwood look alike.
- Grain and texture
- Moderately fine, even texture and straight grain, with low luster.
- Working and character
- Light and very easy to dry, with little splitting or warping, though it can stain. Easy to work, finishes and glues well; not durable.
- Uses
- Carving and sculpture, pattern making, picture frames and drawing boards.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-26.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for jelutong 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 | 15% MC |
|---|---|---|
| Bending strength (MOR) | 5,600 psi (39 MPa) | 7,300 psi (50 MPa) |
| Stiffness (MOE) | 1,160,000 psi (8 GPa) | 1,180,000 psi (8.1 GPa) |
| Crushing strength (compression parallel to grain) | 3,050 psi (21 MPa) | 3,920 psi (27 MPa) |
| Shear parallel to grain | 760 psi (5 MPa) | 840 psi (6 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 390 lbf of side hardness at 15% moisture content for jelutong, 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 (0.36) for jelutong, so it is moved to 12% with the volumetric shrinkage of 7.8% (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 26 lb/ft³, or 2.2 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources