Pit-sawing[edit | edit source]
Pit-sawing continues to be widespread in rural areas of developing countries. It is used for cutting boards and planks at the felling site without transporting the logs. The sawnwood is mainly used locally as building material but sometimes it reaches distant markets. Pit-sawing provides jobs for many thousands of workers.
Pits are dug and large logs are easily rolled across for sawing. However, it is more convenient to set up a stand on which the log is placed (1). The saw cut is marked with a string soaked in moist charcoal dust (fines). A plumb line is fixed to the end of the cut to guide the worker standing on the ground. This worker should wear a wide-brimmed hat as a protection against sawdust. The saw cuts only on the way down but the worker standing on the log has the heavier job because he has to lift the saw up to shoulder height. Therefore, both workers should change places regularly.
The pit saw is tapering in shape (2). Depending on log size, pit saws may vary in length from 150 to 300 cm. Different types of handles are used. An example is given of a lower handle (3a) and an upper handle (3b), both of which must be easily removable.
The shape and size of the teeth is indicated in illustration 4. The height of teeth is from 15 to 20 mm, the distance from tooth to tooth from 20 to 25 mm, the front edge angle varies from 100 to 105° and the near edge angle from 20 to 25 mm.
Maintenance includes the following operations:
- jointing (as for cross-cut saws);
- gulleting (with round-edge millsaw file);
- sharpening of teeth (with millsaw at an angle of 90° with the saw);
- setting of saw (as for triangular cross-cut saws, saw set 0. 8 mm);
- bevelling (teeth pointing away are given a slight bevel of about 5°).
The measures given must be adapted to size of log and hardness of wood.
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