Kawasaki Heavy Industries Ltd. excessively ground down a steel component in 2007, likely causing the 16-cm crack that was discovered in December on the undercarriage of a shinkansen, West Japan Railway Co. said Wednesday.
The thinnest part of the component was 4.7 mm, 3.3 mm less than designed, the railway operator said.
JR West found 100 shinkansen undercarriages with similarly over-grounded parts. The operator, however, has found no immediate safety problems because it has confirmed that there were no cracks in the parts through tests using ultrasound monitoring devices.