Hi rhodesy, normally you would just run Chamfer, select the vertices which want to chamfer (if this is a polyline and not individual line objects) and then enter 5.

Here is a quick demo of this:




If this is not working as expected for you, maybe you have run into a bug... Can you please post the 3DM file with your lines in it so I can take a look at them?

Actually in general if you would also post a 3DM file with your objects in them in addition to (or even in place of) a screenshot, that would help a lot in answering your questions, because I cam more easily examine your objects in the 3DM file.

- Michael