génératrices des diamètres extérieurs

16:24 Nov 27, 2018 

I think Tony has given a good explanation of what this means. However, I think to express it in English you might need to get away from the generatrix and diameter ideas. So, for example, if the shape was a cylinder, you'd put your rulers on the outer surface parallel to the axis of the length of the cylinder. If the cylinder was perfect your rulers would be both in contact with the surface for their entire length and parallel to each other.

15:35 Nov 27, 2018 

I think using 'edges' actually introduces a potential ambiguity that isn't there in the source text :-(

14:57 Nov 27, 2018 

"... on the edges forming the external diameters of the half couplings"

14:37 Nov 27, 2018 

Thanks Tony - one of the difficulties of this document is that all the diagrams have been greyed out!

14:33 Nov 27, 2018 

First of all, do try a term search on génératrice' and variants — this old chestnut comes up regularly, and always gives people headaches!
We do indeed use the word 'generatrix' in EN for the same geometrical concept; however, this is probably not a term that the average maintenance technician would be familiar with. It basically means 'the line that by diplacing rotationally round a centre forms the shape in question' — so the generatrix for a cylinder would be a straight line parallel to the axis of rotation, while that of a cone would be a straight line at an angle to the axis.
If you have any diagrams, you'll probably be able to fiigure out which bits they're talking about, and describe thm in other terms. Without a diagram, it's a little difficult to visualize what they mean here.