A head saw, framesaw, gang saw or head rig, is thesaw that makes the initial cuts in a log at a sawmill, turning a log into cants, or planks of wood.
gang saw,The original powered head saw was composed of long, narrow blades that used an up-and-down motion, a reciprocating saw. Each blade was set at a fixed width meaning each log was cut identically, regardless of flaws.
gang saw,This design was not energy efficient and around 1860 sawmills began to adopt the more efficient circular saw. In the 1870s, the limitation of log size due to the radius of the circular saw was improved with the introduction of the double circular saw- with one blade atop the other. In the 1880s, the band saw was introduced and was able to allow the head saw to handle logs of nearly unlimited size, ideal for the Californian redwoods.
Gang saw blades
For the precision cutting of natural stones, the gang saw blades of variable dimensions and capacities are serving all types of marbles and other materials plants (except granite) for well-shaped blocks.
Fixing the block
gang saw,As far as possible only use blocks of consistent length corresponding to the effective segmented length of the diamond blades. In this way there will be a regular wear of the diamond segments. Sound securing of the block is essential because in practice this leads to reduced sawing vibrations, lower wear on the segments and higher down-feed speeds.
The quantity, quality and good distribution of water for cooling are important factors affecting the blade life and the quality of the cut. Soft well-decanted water should therefore be used, especially when working with materials giving rise to sticky or abrasive muds.
gang saw,The down-feed speed is an essential parameter in frame-sawing. It affects not only the production per hour but also the quality of the cut and the pressure exerted on the segments to avoid glazing of the diamond impregnation. In any case the down-feed speed should be sufficient to ensure the self-sharpening process of the diamond segments.
Start the saw using a low down-feed speed. As soon as the blade’s segments bite into the material gradually increase the down-feed speed till normal working speed is reached. This should be maintained until the whole block is cut.
gang saw,In dealing with the same quality of stone – and this is the case for quarries – it is possible to decide on and maintain an optimal speed. However this cannot be done when successively sawing various different materials. In this case not only should feed speeds be modified, according to the nature of the stone, but different types of stones should be alternated. Sawing therefore should be carefully planned both to ensure a maximum blade life and to avoid frequent mounting and dismounting of blades.
In sawing various types of materials on the same machine – in the case of marbles – nearly always the same blades are used, whereas the ideal solution would be to employ two, or sometimes three, sets of blades of different types. However it is logical to use a single set of blades, and in fact this will be effective provided that the materials are classified beforehand, according to their hardness and their abrasiveness. Moreover the down-feed should be appropriate to each material and there should be an alternate sawing of hard or compact materials and soft or crystalline ones.