Wood species
Bur oak wood
Bur oak is a hardwood (Quercus macrocarpa). At 12% moisture content it has a Janka hardness of 1,370 lbf (6,094 N) and it weighs about 45 lb/ft³ (717 kg/m³), 3.7 lb (1.69 kg) per board foot.
Also called: Quercus macrocarpa.
Key numbers
- Janka hardness, 12% MC
- 1,370 lbf (6,094 N)
- Green: 1,110 lbf (4,938 N)
- Weight at 12% MC
- 45 lb/ft³ (717 kg/m³)
- 3.7 lb per board foot
- Specific gravity (oven-dry weight)
- 0.64 at 12% MC volume
- 0.58 on green volume
- Shrinkage, green to oven-dry
- 8.8% tangential
- Radial 4.4%, volumetric 12.7%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; bur oak's density is worked from its specific gravity with the Handbook's own equation.
How much bur oak moves
A 12 in wide flatsawn board of bur oak that goes from 6% to 12% moisture content swells about 0.22 in (about 7/32 in, 5.7 mm). Quartersawn, the same board moves about 0.11 in (about 3/32 in, 2.8 mm). Flatsawn faces move 2 times as much as quartersawn ones, because the wood shrinks 8.8% around the growth rings but only 4.4% across them.
Worked with the Wood Handbook's dimensional change coefficients for bur oak (Table 13-5: 0.00312 tangential, 0.00151 radial per 1% change in moisture content), which hold between 6% and 14%. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Generally grayish brown heartwood; nearly white sapwood about 1 to 2 in. wide.
- Grain and texture
- Heartwood pores usually plugged with tyloses; broad, conspicuous rays on quartersawn faces.
- Working and character
- Somewhat heavier than red oak, and its heartwood has good decay resistance.
- Uses
- White oak goes into tight barrels, boat planking and bent parts, furniture, flooring, doors and millwork.
The Handbook describes the white oaks as a group; this page gives this oak’s own tested figures.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-9.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of bur oak tested by the Forest Products Laboratory (Wood Handbook Table 5-3b). Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 7,200 psi (50 MPa) | 10,300 psi (71 MPa) |
| Stiffness (MOE) | 880,000 psi (6.1 GPa) | 1,030,000 psi (7.1 GPa) |
| Crushing strength (compression parallel to grain) | 3,290 psi (23 MPa) | 6,060 psi (42 MPa) |
| Compression perpendicular to grain | 680 psi (5 MPa) | 1,200 psi (8 MPa) |
| Shear parallel to grain | 1,350 psi (9 MPa) | 1,820 psi (13 MPa) |
| Tension perpendicular to grain | 800 psi (6 MPa) | 680 psi (5 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
Buying and finishing bur oak
Work it out for your project
- Rank woods for furniture with the species picker
Weigh bur oak against other woods on hardness, weight, movement and color, every figure from the Wood Handbook.
- Plan a finish for furniture in bur oak
The finishes whose makers name that use, and a dated coat schedule from each product’s own sheet.
Why these numbers
Why these numbers?
The situation
The USDA Forest Products Laboratory measured bur oak at 1,370 lbf of side hardness at 12% moisture content, on clear, straight-grained samples (Wood Handbook Table 5-3b).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , 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, the authority for species properties it measured , sources [1]
So
Density at 12% is water's density × specific gravity × (1 + 0.12) (Handbook Eq. 4-14): 62.43 × 0.64 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 45 lb/ft³, or 3.7 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources