Graham, I'll give it a try.
Brian, I agree, but I don't use tool diameter compensation but do think it's a toolpath error. I measured the excess move as 0.89mm but that could easily have been 1mm (2mm cutter but also diameter of top small hole) when cut. Strange as it didn't happen on an earlier iteration. Possibly the vertical move from the small hole to the top horizontal line being miscalculated in Mach3 but correct values showing on displays???
Final article (after judicious use of a file
)
two of these:-
and one of these:-
plus one of these:-
which started life as an old audio power amp case (back panel now modified)
make up an 8x230W per channel high-end audio Home Theatre amp from commercial modules.
Would have been quicker to use a saw and drill press, but much more satisfying to use CNC toys