Pipes with a bell or flange end are most often broken or cracked on the straight or spigot end, and when this occurs, the damaged portion may be cut off and sold as scrap while the remainder of the pipes may be salvaged as sound short lengths. Spun cast iron pipes are quite easily cut with a cold chisel. For sizes up to 10-in., a cold chisel about 1-in., wide and a 4-lb. hammer should do the job satisfactorily. For sizes over 10-in, to 20-in., a blacksmith's cutter and 6-lb. hammer give the best results.
Method - Place under the pipe where the cut is to be made a suitable piece of timber; a piece of 4-in. X 2-in., would do. The purpose of the timber is to assist in turning the pipe during cutting operations. It also provides a solid foundation when the chisel is struck by the hammer. This point is important because after the pipe has been nicked around with the chisel it is the jar from the hammer that causes it to crack off, therefore it is necessary to have a solid support. The timber under the cut also ensures that when the piece breaks off it breaks clean and does not leave a ragged edge.
After placing the pipe on timber, measure from spigot end the length to be cut off. Spot the distance in several places on the circumference of the pipe, then place piece of string or tape round the pipe, lining up the spots, and scribe with pencil or sharp-pointed instrument. Next take chisel, and hammer and cut on line, turning pipe so that the blows take place on the top of the pipe. (It will be found that when the cut has been deepened the blows are more effective on the top of the pipe.)
The first cut around the pipe should be done lightly; each successive time around the blows should increase in weight. This is explained by the fact that, if the blows are too heavy before any depth is cut into the pipe, longitudinal cracks appear in the pipe, which means the pipe would have to be cut again. The chisel should be drawn through the cut, allowing the cutting edge to overlap slightly the previous position. This provides a more uniform cut and causes the break to come away clean.
After about three times around it should then be noticed that a fracture has occurred at one point. The chisel and hammer are the applied near the fracture, which progresses until the piece drops off.
An investigation into the cause of unexplained hairline cracks in centrifugally spun cast iron pipes eventually showed that these were due to the cooling process. The pipes were apparently laid on the open ground, while still warm, and contact of one section of the pipe with the cold earth caused an uneven cooling, resulting in this hairline splitting which was observed at destination.
- Commodity Name:
CAST IRON PIPES