SAWING OFF THE PILES. When piles are driven, it is generally necessary to saw them off either to bring them to the same height, or to get the tops lower than they can be driven, or to secure sound wood upon which to rest the timber platform that carries the masonry. When above water, piles are usually sawed off by one man using an ordinary hand saw or by two men using a cross cut saw; and when below water, by machinery—usually a circular saw on a vertical shaft held between the lea:lers of the pile driver or mounted upon a special frame, and driven by the engine used in driving the piles. The saw-shaft is sometimes attached to a vertical shaft held between the leaders by parallel bars, by which arrange ment the saw can be swung in the arc of a circle and several piles be cut off without moving the machine. The piles are sometimes sawed off with what is called a pendulum saw, i.e., a saw-blade fastened between two arms of a rigid frame which extends into the water and is free to swing about an axis above, the saw being swung by men pushing on the frame. The first method is the better, particularly when the piles are to be sawed off under mud or silt.
Considerable care is required to get the tops cut off in a hori zontal plane. It is not necessary that this shall be done with mathe
matical accuracy, since if one pile does stand up too far the excess load upon it will either force it down or crush the cap until the other piles take part of the weight. Under ordinary conditions, it is a reasonatly good job if piles on land are sawed within half an inch of the same height; and under water, within one inch. When a machine is used on land, it is usually mounted upon a track and drawn along from pile to pile, by which device, atter having leveled up the track, a whole row can be sawed off with no further attention. When sawing under water, the depth below the surface of the water is indicated by a mark on the saw-shaft, or a target on the saw-shaft is observed upon with a leveling instrument, or a leveling rod is read upon some part of the saw-frame. In sawing piles off under water, from a boat, a great deal of time is consumed (particularly if there is a current) in getting the boat into position ready to begin work.
Piles are frequently sawed off under 10 to 15 feet of water, and occasionally under 20 to 25 feet.