On Wed, 3 Jan 2024 at 22:01, andy pugh <bodge...@gmail.com> wrote: > This means that the large and small arcs are tangent to each other, > which requires that their centres lie on a perpendicular line, and > that in turn means that the arc centres of small and large arcs must > be coincident.
Close, but no cigar, it seems. There is an equation in an online document (https://archiwum-bazakonkurencyjnosci.funduszeeuropejskie.gov.pl/file/download/587886) that isn't actually correct: x'= Dm/2×cosØ −2×e×cos(2Ø)+e×cos(4Ø) y'= Dm/2×sinØ -2×e×sin(2Ø)+e×sin(4Ø) However, after getting hold of a pirate copy of the standard, it turns out that it was only slightly wrong. This is what it should be. ( -+++ not -+-+) x'= Dm/2×cosØ −2×e×cos(2Ø)+e×cos(4Ø) y'= Dm/2×sinØ +2×e×sin(2Ø)+e×sin(4Ø) Plotted out this is very close to the shape that I had but differs by about 30 microns at the worst spots. The good news is that this is very easy to convert to either XY offsets for boring, or a radius for computed offset on a lathe as it is already in terms of spindle angle Ø. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
