As a result of recent investigations, and with the aid of a modified form of cutting blowpipe, it is now possible to successfully cut all grades of cast iron up to 12 or 14 inches thick, the resulting cut being slightly wider and coarser than that obtained when operating on steel.

The cutting blowpipe for cast iron is similar in construction to the Universal " S " type cutter, but is designed for working with an oxygen pressure of not less than 70 lbs. per square inch. For prolonged cutting and on heavy work a battery of oxygen cylinders with a heater should be employed, otherwise the regulator is liable to freeze, whilst the battery of cylinders obviates the necessity for continually stopping the work in progress in order to change cylinders.

An ample supply of acetylene is essential, the ordinary type of portable generators usually being unsuitable, as they are not capable of supplying the quantity of gas required without overheating. The generator should take a charge of not less than 281bs. of carbide and be capable of continuous production of gas.

A special large size of hydraulic back pressure valve is desirable, or two hydraulic valves of standard size may be coupled together, otherwise the passage of the large quantity of acetylene required through the valve is liable to displace the water with which they are charged.

Dissolved acetylene may be used, but, again, an ample supply of gas is essential, and to obtain this condition it is necessary in practice to couple two, three or four cylinders together by means of a suitable connector, using a regulator set to deliver the gas at not more than 5 lbs. per square inch. When cutting, the blowpipe must be given a slight sideways movement in order to widen the cut and allow a free passage for the oxide through it. Very little movement is necessary, about 3/4 inch from side to side being usual, the cutter proceeding in a zig-zag fashion along the line of cut, this producing the slightly wider cut required.

The complete equipment consists of five units :-(1) The cutting blowpipe : (2) The oxygen pressure regulator ; (3) the hydraulic back pressure valve ; (4) the acetylene generator ; (5) the oxygen cylinder.

Referring to unit (1) it should be noted that the Company manufactures two types of hand metal cutting blowpipes :-(a) The Universal metal cutting blowpipe, illustrated and described further on. (b) The " S " type metal cutting blowpipe ; this cutter is a later development of the original " Universal n type, and is illustrated later. Both of these cutters are the outcome of long and specialised experience, and their particular advantages are :-

Fig. 49.

First

All controlling valves are located at a point farthest away from the heating and cutting nozzles, and are under the hand of the operator.

Second

The combined thumb screw and lever control for the cutting oxygen supply valve enabling the advantages of either lever control or screw-down valve control to be obtained at will.

Third

The ease with which the essential parts of the blowpipe may be detached and reassembled again. The " S " type cutter can be completely dismantled in a few minutes by unscrewing a few union nuts.

We will now proceed to illustrate and describe the various units in the order given above, starting with :-