Glossary
Slope of grain
Also called: cross grain, grain deviation
Reviewed
Slope of grain is the angle between the wood fibers and the long axis of a board, stated as a ratio such as 1 in 4 (the grain drifts 1 in across for every 4 in along). The Uniform Standard allows a maximum slope of grain of 1 in 4 in pallet parts, for both reusable and single-use pallets.
How slope of grain is measured
Follow the grain lines along the face or edge of a board. If the grain crosses 1 in of width while running 4 in along the length, the slope is 1 in 4. A steeper slope, such as 1 in 3, means the fibers run out of the board sooner.
The limit
| Use class | Maximum slope of grain (Uniform Standard 2012, Table 1) |
|---|---|
| Reusable | 1 in 4 |
| Single-use | 1 in 4 |
Unlike knots and wane, the slope-of-grain limit is the same for both use classes.
Why it matters
Wood is much stronger along the grain than across it. When fibers run off the board's axis, bending loads pull partly across the grain, so steep cross grain can let a deckboard or stringer break at a low load. Short, steeply sloped grain is also where splits start. See lumber grades.
Questions
- What does 1 in 4 slope of grain mean?
- The grain drifts 1 in across the board for every 4 in of length. That is the steepest slope the Uniform Standard allows in pallet parts.
Sources
- Uniform Standard for Wood Pallets (NWPCA, now Woodpack Global), 2012 edition