Sawmill Overrun and Lumber Recovery Factor

Overrun is a property of the SCALE RULE, not only of the mill, and comparing it month to month without tracking log diameter measures the log mix. A mill scaling 1,000 board feet Doyle and tallying 1,240 shows 24.0% overrun -- but on 10 in logs Doyle's fixed 4 in slab allowance is so far off that the rule ALONE would give 65.6% if the mill cut the International 1/4 volume, so 24% on small wood is not a good month, it is a conservative scale. On 20 in logs the same bias is only 15.3%, and the same 24% would be excellent. THE MEASURE THAT DOES NOT MOVE WITH THE SCALE RULE IS RECOVERY. Those 1,240 board feet from 210 cubic feet of log is 5.90 board feet per cubic foot, and against a 7 benchmark for a well-run hardwood mill that is 15.6% short -- and it says the same thing whether the logs were scaled Doyle, Scribner, or International. Recovery responds to what a mill controls: kerf, sawing accuracy, target sizes and oversize for shrinkage, edging and trimming, and how the sawyer breaks down each log. KERF IS THE LEVER WITH A NUMBER ON IT. Dropping from a 0.180 in band to a 0.125 in band on 1 in boards recovers 4.9% more lumber from the same logs, 61 board feet on this tally, and takes the sawdust share of the wood cut from 15.3% to 11.1%. The commercial point that follows all of it: overrun on a conservative scale is not free money, because the log price already reflects the scale. Improving recovery is real; improving overrun by buying smaller logs is not. A ratio calculation from volumes the user supplies. Overrun is not comparable between mills, between scale rules, or across a changing log mix. It does not compute log scale itself, and it does not address scaling deductions for defect, which materially change the scaled volume and are a matter of the scaler's judgment and the applicable scaling handbook. It does not evaluate GRADE recovery, which is where hardwood value actually sits, or value recovery per log, and it does not address green versus dry tally or the shrinkage allowance in target sizes. The applicable scaling rule and handbook, the grading rules of the applicable agency, and the mill's own scaling and tally records govern.

overrun = (tallied board feet - scaled board feet) / scaled x 100; lumber recovery factor = board feet produced / cubic feet of log input; the scale-bias comparison is the Doyle rule (D - 4) squared x length / 16 against the International 1/4 rule (0.22 D squared - 0.71 D) per 4 ft section at the same diameter and length.

The standard mill definitions of overrun and lumber recovery factor by name, with the public-domain Doyle and International 1/4 log rules. The applicable scaling rule and handbook, the grading rules of the applicable agency, and the mill's own scale and tally records govern.

Ratio arithmetic on the mill's own scale and tally figures; the log rules used are public-domain formulas, and no proprietary scaling table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: scaled_bf, actual_bf, log_volume_cuft, benchmark_lrf, avg_log_diameter_in, log_length_ft, kerf_in, target_kerf_in, board_thickness_in, overrun_pct, recovery_bf_per_cuft, scale_bias_overrun_pct, doyle_bf, international_bf, kerf_gain_pct, sawdust_share_pct

• Overrun measures the scale rule and the log mix, at least as much as it measures the milllog scaling practice
• Recovery is the comparable number board feet per cubic foot does not move with the scaling conventionmill practice
• Grade recovery is where the value is a mill can raise volume recovery and lose money by degrading gradethe applicable grading agency