I was on the hammer and tap, drilling rock, as my comrades were … We started off having to drill 80 centimetres a day; we finished up having to do 3 metres …
[Tom Uren, quoted in Gavan McCormack and Hank Nelson, The Burma–Thailand Railway, Sydney, Allen & Unwin, 1993, 53.]
Cuttings such as Hellfire Pass (Konyu Cutting) formed a critical function on the Burma-Thailand railway as they allowed the rail track to climb at a steady gradient. The task of carving cuttings deep and wide enough to allow the railway to pass through mountainous terrain was colossal, particularly as much of the excavation had to be done without modern equipment.
There were numerous cuttings along the railway. They could range from small incisions in the hill, forming a 'bench' levelling out a particular stretch of track, to deep chasms in the rock such as Hellfire Pass.
The first step in excavating a cutting was to clear the area of vegetation. Then loose soil could be cleared relatively quickly using hand tools. Where the ground was semi-marbleized limestone (as at Hellfire Pass) however, the clearing work was more time consuming and difficult.
A common method of drilling the rock was 'hammer and tap'. One man would hold a drill—the 'tap'—while another drove it into the rock by wielding a hammer (of 3.6 to 4.5 kilogram or 8 to 10 lb). After each blow from the hammer man, the tap man would rotate the drill to prevent it from becoming stuck in the rock. Three progressively longer lengths of tap were used as the prisoners drilled deeper into the rock.
The rock powder was then extracted by pouring water into the hole and scooping out the resulting mud with a long spoon.
Dynamite would be placed after a series of holes were finished. Hugh Clarke, an Australian prisoner of war, recalled:
The engineers would plug it with dynamite, get six or seven of us out and give us a cigarette. We would light a cigarette each. We would have to light four or five fuses and then go for our lives up into the bush before the charges blew.
['Of elephants and men' in Gavan McCormack and Hank Nelson (ed.), The Burma–Thailand Railway: memory and history, Sydney, Allen & Unwin, 40.]
After the dust had settled, the hammer-and-tap pair would move to another section while other gangs of prisoners moved the rubble. After breaking it up with shovels, picks and chunkels (hoes), they would carry it out using sacks or bamboo baskets. Where a cutting was deep, human chains would be formed to carry earth up ladders and over the side of the cutting. In some cases, skips on light rail were used to move the earth.
The Japanese engineers set daily quotas for each prisoner. For a hammer and tap pair, the initial quota was one metre of drilling per day. However, the Japanese quickly increased this, so that during the 'Speedo' period in mid-1943 each team was drilling at least three metres. To complete this, men were made to work for up to fifteen, even eighteen, hours a day.
At some worksites compressors were used to power jackhammers to dig through the rock. However, these were bulky, in short supply and prone to breakages. Compressor Cutting, about four kilometres beyond Hellfire Pass, was named after these machines. Elephants were also sometimes used: for example to carry water for use in extracting dust from the hammer and tap holes.
Work on cuttings was exhausting and dangerous. It was easy for a hammer man, tired and malnourished, to slip and hit his partner holding the tap, crushing his fingers. Rock splinters from the drilling and the explosives could easily cause skin and eye injuries. Sharp rubble was also a hazard to men whose shoes and clothes had long since worn away in the humid climate. Any injury incurred in the construction of a cutting was compounded by the lack of medicine available to doctors and the poor food provided to prisoners. Even a small cut from sharp rock could become infected and turn into a tropical ulcer.