Posted by dellus on Aug 08, 2017; 9:35pm
URL: https://forum.librecad.org/Trimming-unwanted-arcs-from-a-circle-tp5715167p5715185.html

Don't use a rectangle as a limiting line, as it is seen as one entity and not as four single lines, some operations don't work. So draw two parallel lines, or 'explode' the rectangle.
I'm not sure I understand what you are describing (an image might be helpful), but if understand it right you can achieve success by using 'divide' instead of 'trim'. Thus you can cut apart the circle at the intersection points (snap) with the parallel lines and then delete the small inner circle part.
That with the gaps isn't clear to me. In the tab appearing when doing the fillet operation you can set the radius and also choose to trim or not. If trim is set it might do stupid things. In that case uncheck trim and do necessary cuttings with 'divide'. Or try to repair the gaps with using 'trim' to extend entities.