Abstract The fracture toughness properties of two spun cast, ferritic SG iron pipe samples have been investigated and the results compared with previous work. It was found that the COD at fibrous crack initiation ( δ i ) was independent of: (a) specimen size; (b) machined or fatigue precracking and (c) graphite nodule number and spacing. This is discussed with respect to the fracture initiation mechanism which was found to be independent of graphite nodules. The maximum load COD values and COD transition were similar for fatigue cracked and machined slit specimens. The COD values and COD transition temperature obtained from spun cast pipe are lower than those obtained in previous work on SG iron and it has been shown that the maximum load COD decreases with decrease in graphite nodule spacing. The effect of graphite nodule spacing on the ductile fracture propagation energy is discussed.