Log yield, also called lumber recovery, is the share of a log's volume that ends up as sawn lumber. For pallet stock, yield depends on log diameter, taper, saw kerf, sawing accuracy and the cutting pattern chosen, and small gains matter because pallet lumber is a low-margin product where raw material is the largest cost.
What yield means
Mills report recovery in two ways. Volume recovery compares the volume of lumber produced with the volume of logs sawn, usually in cubic meters, or in North America as the lumber recovery factor (LRF) in board feet per cubic foot of log or per log volume unit. Value recovery compares the market value of the products with the cost of the logs, and is more relevant when grades differ.
Pallet makers need volume and the right product mix: 20–25 mm boards, stringer and block cants, and cut-to-length pieces. A pattern that wins on volume may lose value if it makes too many pieces that do not match the pallet cutting list.
Log recovery is the product of several factors. A US Forest Service study of lumber recovery identified seven major influences, and demonstrated how large the effects of kerf, sawing accuracy and cutting pattern can be.
Factors that determine yield
| Factor | How it affects yield | Example finding (US Forest Service study) |
|---|---|---|
| Log diameter | Larger logs give higher recovery because the proportion lost to slabs and edgings falls | Computer modeling showed recovery rising with diameter for all taper classes |
| Taper | Logs that narrow rapidly waste outer wood when cut to uniform widths | Included as a major factor |
| Kerf | The wood turned to sawdust by each cut | Cutting kerf from 12/32 to 9/32 in (9.5 to 7.1 mm) raised yield by about 7% for logs 5.5–12 in (14–30 cm) in diameter |
| Sawing accuracy | Variation in board thickness requires extra allowance | Improving accuracy from 0.2 to 0.1 in (5.1 to 2.5 mm) raised board-foot yield by 6% |
| Cutting pattern | Where the saw lines fall on the log | A 0.2 in shift of log position on an 8 in log gave 25% more lumber in one case |
| Product mix | Allowing narrow or short boards uses outer wood | Adding 1×4 lumber to the product list increased recovery by 9.7% on a 7.1 in log |
| Edging and trimming | Deciding where to cut away wane | Computer-optimized edging reached 97% of theoretical optimum |
These figures come from a computer-simulation study of older sawmill technology, so they illustrate relative effects rather than guaranteeing results in a modern mill.
Cutting patterns
A cutting pattern describes how the saw lines are laid across a log's end. Common patterns for pallet stock include:
Live sawing (through-and-through)
The log is sawn straight through into parallel boards, which are later edged. Simple and fast; wane stays on the outer boards until edging.
Cant sawing (cant and side boards)
The log is first cut into a central cant: a squared or rectangular beam. Side boards are cut from the two outer faces. The cant is then resawn into boards or used whole as a stringer, block stock or beam. Cant sawing is the basic pattern of chipper-canter lines and many pallet mills.
Grade sawing
Boards are cut and rotated to place knots and defects where they do the least harm. This is used mainly for high-grade hardwood and is less common in pallet stock.
Cutting to the pallet cutting list
Pallet-specific mills may cut cants to the exact cross-section of stringers or blocks, and boards to the dimensions in the pallet design; see pallet blocks and custom pallet design.
Small-diameter logs
Pallet mills use logs that sawmills producing construction lumber would not take: small, crooked, knotty or low-quality pieces, and the cores and outer slabs from larger logs. These logs have a high percentage of wane and slab and so have lower recovery in volume terms, but they are cheap.
Techniques for small logs include:
- Chipper-canter lines that handle small, straight softwood logs at high speed and produce standard cants.
- Multi-rip gang saws that cut a cant into several boards or blocks in one pass; see multi-rip saws.
- Band resaws with thin kerf for resawing cants and slabs; see resaws and band resaws.
- Slab recovery: edging the outer slabs to recover narrow boards for blocks and pallet parts.
Wood species and log quality also change yield; see wood species used for pallets and spruce and fir.
Optimization and scanning
Computerized scanning lets mills choose a cutting pattern for each log. Industry coverage of pallet sawlines describes the main technologies: LED shadow scanners measure log diameter, taper and length; laser-camera combinations build 3D images that account for sweep and crook; linear scanners position infeed and cutting heads; and transverse scanners at the edger identify wane to maximize usable board width. As the article notes, high-recovery softwood canter lines are often shut down when the scanner and optimization system fails, because manual operation cannot match its recovery.
The Forest Service study showed why: the best opening face system, which chooses the position of the first cut, increased recovery by an average of 21% for logs of 5–20 in, compared with a standard approach. In practice, results vary with mill type, but optimization is a key driver of profitability.
Practical steps to improve yield
- Sort logs by diameter so that each class is sawn with the right pattern.
- Reduce kerf through thinner saws where the machinery allows.
- Maintain saw accuracy. Worn guides and dull blades cause variation, so check board thickness regularly; see pallet machinery maintenance.
- Match the product mix to the cutting list so that every piece has a use.
- Use co-products. Chip slabs and edgings for pulp or biomass, which improves overall economics; see pallet wood waste and biomass.
- Measure. Track recovery per log class and per shift, and examine outliers.
The broader process is described in how a sawmill works.
Frequently asked questions
What is lumber recovery factor?
LRF is a measure of lumber output per unit of log input, typically board feet per cubic foot of log. A higher figure means more of the log becomes lumber.
What is a cant?
A cant is a log squared on two or four sides. It may be sawn into boards or used whole as a stringer or block stock.
Why does kerf matter?
Every cut turns a strip of wood into sawdust. Thinner kerf yields more lumber from the same log, which is why band saws and thin-kerf blades are preferred.
Are small logs worth sawing for pallets?
Yes, because logs are cheap and pallet components can be cut from small cants and slabs. Yield per log is lower, so efficient machinery and scanning are essential.
Sources
- Lumber recovery (General Technical Report FPL-39) — USDA Forest Products Laboratory
- Sawlines: Scanners, Computers Optimize Machines — Pallet Enterprise
- Wood Handbook: Wood as an Engineering Material — USDA Forest Products Laboratory