Hi All,
Many years ago I worked at Stone Manganese Marine in E London as part of my Metallurgy Sandwich Degree course.
While there I followed a project for a LARGE ships propeller in a then brand new Ni-Cu-Mn alloy called Sonoston; this was being developed for use on naval propellers, (submarines I think),
The alloy had very low magnetic properties and also was acoustically "dead", you could whack it with a hammer and it was almost like hitting lead.
The moulds for the props were built into the floor of the foundry and there were huge design problems as the alloy had a HUGE shrinkage rate when it cooled which made the final complex shape very hard to achieve.
When machined on HUGE lathes the final fine work was done by a chap with large files and small angle grinders.
Cheers Martin
Amazing to watch the pour of many, many tons of metal and the dexterity of the workers also amazing.