Wire Ropes And Tightening Screws 263

Fig. 231.

Wire Ropes And Tightening Screws 264

Fig. 232.

Wire Ropes And Tightening Screws 265

Fig. 233.

The Circular Saw Bench (Fig. 231) consists of a strong cast-iron frame or table, the top of which is planed true, and has a narrow slot near its centre through which the upper part of the saw runs, the saw itself being carried on a spindle of steel fitted to run in bearings just below the surface of the table. This spindle is caused to revolve rapidly (from 800 to 1200 times per minute) by means of pulleys keyed on to it and a belt running round them. In order to ensure a uniform thickness of the wood being sawn, a guide plate, adjustable by means of a hand wheel and screw, is fitted at one side of the table, and by its means the thickness of the plank or board to be cut can be gauged with the greatest accuracy. The power taken by these saw-benches is somewhat high, and the waste of wood much greater than caused by hand sawing, but the great saving in time and labour far outweighs these considerations. There are many different makes of saw bench, some of them having a great variety of adjustments, such as rocking tables, automatic feeding apparatus, etc. The one illustrated is, however, quite sufficient for all ordinary work of moderate dimensions.

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Fig. 234.

The Planing Machine (Fig. 232) is a power-driven apparatus for taking timber out of "wind" or twist, surfacing straight or taper, levelling, chamfering, squaring up, making glue joints, etc. It consists of a table, planed true, supported by a pillar, both of cast iron, the table having a spindle running beneath a central cross slit, the spindle carrying a series of cutters or knives revolving at a rate of about 800 revolutions per minute. The spindle is adjustable vertically as regards the surface of the table, and can be regulated to take a greater or less cut off the surface of the timber passed over it. The machine is also provided with an adjustable guide or fence at one side of the table The Mortising Machine (Fig. 233) is a hand-power device for forming the mortise of the much used mortise and tenon joint in joinery. It consists of a cast-iron frame having a movable table, actuated by a hand wheel and an upright cast-iron pillar, securely bolted to the lower frame, carrying the spindle, slide bracket, and lever, by means of which the chisel is caused to rise and fall. The material to be mortised is held firmly on the sliding table by a vice, and the chisel is worked up and down vertically by means of the lever with the right hand, while the work is Plant required for Building Work of Moderate Size 129 traversed slowly along by means of the hand wheel with the left. At the end of the mortise the chisel is turned completely round by reversing the spindle, and the operation repeated in the opposite direction, backwards and forwards until the mortise is completed.

Wire Ropes And Tightening Screws 267

Fig. 235.

traversed slowly along by means of the hand wheel with the left. At the end of the mortise the chisel is turned completely round by reversing the spindle, and the operation repeated in the opposite direction, backwards and forwards until the mortise is completed.

A useful combination of this machine with a boring machine is shown in Fig. 234, in which the spindle has both reciprocating and revolving motions.

The Band Saw (Fig. 235), as its name implies, is a saw in the form of an endless band, which is caused to run at a high speed over rubber-covered wheels placed vertically one above the other on a suitable cast-iron frame. The saw passes through a slot in a cast-iron table midway between the wheels, and on this table the material to be worked is placed. With this machine flat timber or plank can be cut to almost any curved or tapered shape. It is also very useful as a cross-cut saw. The top wheel is made adjustable so that the saw can be tightened when necessary - the power for driving being applied to the lower wheel by means of a shaft and pulleys.

The cast-iron table is arranged to cant to almost any angle, this adding considerably to its usefulness in various kinds of work.