Full resolution (JPEG) - On this page / på denna sida - IV. Forestry - 2. Forest Industries. By E. Arosenius
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210
iv. forestry.
bridge into the mill. One end of the log is then attached to a frame on wheels
("log-carriage"), while the other end rests on a cylinder or roller near the
saw-blades. The latter are stretched in a strong swing-frame, which runs up
and down in the bearings of a pair of upright frames. The movement of the
swing-frame is produced by a rod secured to the lower edge of the frame,
whose other end is connected with a crank, which is caused to rotate by wheels.
By means of gearing connected with these, the log-carriage is led forward,
while the sawing is going on. The number of saw-blades in a frame depends
upon the size of the logs and the thickness of the boards to be sawn, so that
the log is sawn up into boards at its first passage through the frame, unless
square-sawing is adopted, which is frequently the case with large logs; in this
case, the logs are first sawn on two outer sides before the sawing proper begins
in the next frame. On account of the evenness of Swedish timber, it has not
been found necessary to make use of band-saws, the working up of the logs
being made almost everywhere by gang-saws, which, in its simplest form, is of
the kind described above; at large saw-mills with modern appliances, special
machines are often used to perform the work more rapidly.
Transporting Timber to the Lumber-yard.
The saw-blades are changed every time a new dimension is to be sawn.
In this respect the large saw-mills have an advantage, as they can with more
facility saw several dimensions at a time without needing to change frames so
frequently. The old saw-blades were rather thick and had a long stroke, so that
they consequently worked slowly and wasted much timber (about 10 %). On
account of the increased prices of timber, and under the influence of competition,
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