In addition to welding, as explained above, acetylene can also be used as the heating agent in a special blowpipe for oxygen cutting. The blowpipe is so arranged that a separate jet of oxygen may be discharged through the centre of the blowpipe flame when the metal is heated up to melting-point. This immediately produces combustion of the metal with the resulting formation of oxide. The jet of oxygen is made sufficiently strong to blow away this iron oxide in front of it, with the result that a clean, narrow cut is effected through the metal at a speed of travel which is comparable with hot sawing. The metal on each side of the cut is neither melted nor injured in any way, as the action proceeds too rapidly for the heat to spread. The cutting may be made to follow any desired line or curve as required.
Some idea of the rate of cutting can be gleaned from the fact that 1/2-in. plate can be cut at the rate of 1 ft. per minute, and boiler plate, of 1 1/2 in. thickness, being cut at about one-half this speed.
The proportionate consumption of acetylene to that of oxygen varies from 25 per cent. for the thinnest section of plate to 10 per cent. for the thickest section of plate.