- 13

4. Effect of Lumber Size on Overrun

—.

The percentage of log volume cut into rough lumber is not
necessarily a measure of mill efficiency. The actual number of board
cet of green lumber produced from a cubic foot of green lumber will
3 1ethor the boards were cut scant, full-size, or over-size.

Table IV shows a comparison of three mills cutting logs of the

le
7 > a co = yoy OQ
same average diameter,

TABLE IV.

The elation of Overrun and Lumber Size

SEEnEEEEEEeeeer eee es ac eere
' ! Diam. i Cut over Nominal Size Total Residue {
=a ! 5 Ove soar eas eal Sn a

esa — Aye le ERD | Thickness | Width | (per cent of |
i ‘ . eG e i ws

inchs oe Ses i inches {| inches { cubic volume)

ee es eee
ae" |} = 20555 One| B15

{
| ! |
*ll.l 0.16 lo Ona sc 40.3
|
{

er 15e0 a loo | eno. | onsa == 3904

*This mill had an underrun.

The percentage of residue in the three mills was fairly uniform.
n Mill A thi lumber was cut heavily oversize resulting in an underrun.
Wi11 C, which cut very close to nominal thickness, had the highest over-

rune

De Board Foot-Cubic Foot Relationships

The percentages of the various forms of mill residue shown in
the preceding tables are sed on the volume of the log sawn and measured

s ba.
in cubic SIE In commercial practice the log volume is measured by the
sakes an allowance for slabs and sawdust and is
Soe in bona feet. o apply the percentage of sawmill residue it

t

is necessary to conver a6 board feet as determined by the B.C. Log

ratio between board feet and cubic feet varies

Scale to cubic feet. The
With diameter, taper, and

| fee a al “of a 156 western white spruce

ividua 1 ae averages varied from a minimum of