All of the gases described for welding are also used for cutting and offer some advantages over other methods of cutting for various purposes. The work is done by heating the metal to about 1500 degrees Fahrenheit with a flame composed of oxygen and the gas used, and then directing a blast of oxygen against the heated surface. At that temperature the iron or steel has a great affinity for oxygen; so the metal is oxidized or burned up so rapidly that a clean cut is made in the piece. The metal is entirely destroyed, of course, but the work is done so quickly and the slot cut is so narrow that it is considered no disadvantage. The metal passes off in the form of an oxide. Pieces of almost any commercial thickness may be cut and blast-furnace tap holes have been cut out to depths of 4 feet of metal.

Fig. 124. Oxygraph for Cutting steel According to Pattern with Oxy-Acetylene Flame.

Equipment For Cutting

The apparatus required for cutting consists merely of a torch, Fig. 121, tubes for the gas and oxygen, and a source of supply of gases. The gases are generally supplied in tubes as for welding, and portable outfits are most convenient for all-around use. The torches used for cutting differ from those used for welding in that an extra stream of oxygen must be carried to the tip end, and this is generally done by an extra tube along one side of the torch. In some forms the oxygen is then carried through the preheating flame, but the most efficient types are those in which the oxygen is brought into contact with the metal just back of the main Same and so directed as to cause the oxygen to strike the hot spot. The composition or hardness of the metal have no apparent effect on the speed of cutting and chrome nickel steel armor plates 9 inches thick can be cut at the rate of 2\ minutes per foot of cut, with oxy-hydrogen flames. Figs. 122 and 123 show heavy pieces which have been cut with hot-flame apparatus. Numerous cutting machines have been devised for automatic work, among which are those for holes, rails, cams, irregular curves, and straight lines, Fig. 124, and they are much more rapid and efficient than hand cutting because of their uniform feed and speed. For work on which they can be used they are a good investment.

Fig. 125. Cutting up the Maine with Gas Blowpipe Courtesy of Oxweld Acetylene Company.

Applications Of Hot-Flame Cutting

The applications of hot-flame cutting are so numerous that only a few of them need be described in order to give a good general idea of its possibilities. The accompanying examples were done with oxy-acetylene, oxy-hydro-gen, and other gases and the work is very similar with all of them. The principal characteristic of the work done is the smoothness of the cut, and the cost compares very favorably with that of cutting with the electric arc. It is cheaper than the arc on moderate and small work but more expensive on large work. The low first cost of the outfit makes it appeal to small shops and scrap dealers, although it is very valuable for cutting up junk and all sorts of wreckage. The battleship Maine was dismantled with an Oxweld acetylene outfit, Fig. 125, and the ruins of the Quebec bridge were also cut away with this apparatus, Fig. 126. Manholes in tanks and boilers, portholes in steel vessels, ruins of burned or wrecked buildings, and, in fact, almost anything of metal may be cut by this process rapidly and conveniently. It is not necessary to have the article in any particular position as the work may be done wherever the operator can carry his torch. Work has been done on the top of high towers and stacks and down in deep holes and in steam vessels, inside locomotives, and on the lower side of bridges.

Fig. 126. Cutting up Ruin., of Quebec Bridge with Acetylene Blowpipe Courtesy of Oxweld Acetylene Company.

Table XV. Cost Of Cutting Per Foot Of Cutting Length

Thickness of iron in inches

1/8 in.

in.

5/16 in.

3/8 in.

in.

5/8 in.

in.

1 in.

1 in.

1 in.

2 in.

Cunsumption of oxygen in cubic feet per foot of cutting length

0.45

0.50

0.60

0.90

1.30

1.90

2.50

3.10

4.00

5.60

7.60

Consumption of acetylene in cubic feet per foot of cutting length

0.12

0.13

0.13

0.18

0.19

0.21

0.25

0.30

0.36

0.41

0.47

Length of time in minutes per foot of cutting length

1

1

1

1

1

1

1 1/3

1 1/3

1

1

1

Total cost in cents per foot of cutting length

1.25

1.35

1.5

2.1

2.7

3.7

4.6

5.7

7

9.5

12.75

Thickness of iron in inches

2 in.

3 in.

4 in.

5 in.

6 in.

7 in.

8 in.

9 in.

10 in.

11 in.

12 in.

Consumption of oxygen in cubic feet per foot of cutting length

8.25

11.80

15.30

20.60

26.00

32.00

37.00

44.00

51.00

59.00

68.00

Consumption of acetylene in cubic feet per foot of cutting length

0.60

0.90

1.20

1.40

1.65

1.90

2.10

2.35

2.70

3.10

3.25

Length of time in minutes per foot of cutting length

2

2

3

3

3

4

4

5

5

5

6

Total cost in cents per foot of cutting length

14.5

20

25

34

42

52

59

71

82

95

108

The cost of cutting steel pieces, per foot of length, using the oxy-acetylene flame is given in Table XV by Messer and Company, Philadelphia, and is approximately correct for other systems.

Cost Of Hot-Flame Cutting

The cost of cutting will depend upon the cost of the gases, cost of labor, the nature of the work, and the facilities for handling it, but a few typical jobs will give a good idea of the possibilities. The accompanying connecting rod forging for a stationary engine is 6 inches thick and the crosshead slots are each 9 inches by 7 inches in size and were cut out in 15 minutes each. The total cost of the operations was $6.00, including labor and gas; whereas the usual method of drilling and chipping would have taken 8 hours for each slot and have cost more. In steel and iron foundries this system is used for cutting off risers and gates from the castings and, in boiler shops, for cutting plates of considerable thickness, cutting off rivet heads, cutting holes, etc. The 4X6 foot plate, ft inch thick, shown in one of the illustrations is a cross brace plate for a locomotive frame and was cut as shown in one hour. The total amount of cutting was 264 lineal inches, which is at the rate of 3 minutes per running foot. Where articles are to be welded after cutting, it is necessary to remove the oxidized surface from the cut before welding. This can be done with a pneumatic chisel.