19 May 2014

Show 'em ... _#9

As the heading suggests, this post is one of a series.
To follow, start with Show 'em what you can do_#1 and proceed in chronological order.
This is a teaching/training/exchange exercise.
Feel free to submit comments or suggestions, including alternative and improved translations.

Block 6

For the French, see Les paris gagnés de DCN

Machining titanium

A submarine’s stern gland provides a high-pressure seal between the shaft line (or propeller shaft) and the hull. In the case of France’s new-generation Le Triomphant-class SSBNs, this vital component takes the form of a machined metal cylinder 1180 mm in diameter by 600 mm in length. Early in the design phase (in 1986), the decision was taken to use titanium, a metal combining the strength of steel with the lightness of aluminium. Titanium has, of course, been used for special items for many years, but never for anything this big.

Working with toolmakers and other specialists, the team developed a range of tungsten carbide cutting tools. Note that titanium presents a special challenge in that mis-machined or damaged parts cannot be repaired. Given the high cost of the raw material, DCN machine tool operators cannot afford to make the least mistake.
Caption: Machining a titanium stern gland for a submarine’s shaft line
Running commentary
  • 'shaft line (or propeller shaft)': the less technical term 'propeller shaft' being both more transparent and widely known from other mechanical contexts, it seems advisable to mention both. 
  • 'cylinder 1180 mm in diameter by 600 mm in length': The original says un cylindre de 1180 mm de diamètre sur 600 de haut. Given that the shaft line is normally horizontal (also that the picture shows the stern gland with its long axis horizontal), it seems more logical to me to use the word 'length' rather than 'height'.
  • carbutiers : to the best of my knowedge, carbutier is not recorded in any dictionary. As of May 2014, Google failed to yield any useful information concerning the singular or plural form, save for one hit concerning carburettor (carbu) technicians. This DCN workshop term probably refers to the fact that machine tool cutting tips are generally made of carbure de tungstène or tungsten carbide (Wikipedia articles in English here and in French here).[I note in passing that Google has, apparently, failed to index the instance of 'carbutiers' on the page under discussion, possibly because it is too far down the page. Interesting.]
  • si ça casse, il n'y a aucune solution de réparation : My redrafting of this passage is more explanatory, partly because I failed to find a succint idiomatic expression corresponding to the popular French forumalation si ça casse (literally 'if it breaks', which is neat, but does not sit easily with the rest of the sentence).

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