old as "irt"? you are slipping on us
Krumley had asked about tangential control of a 4th axis. I too use desk cnc on my machine, but as far as ive ever seen, it provides no way to do this. It will operate the 4th axis, if the g code is provided, but you cant create that tangential information with it. the Mach software will create the 4th axis rotational info "on the fly" i guess by comparing the x and y values and determining the actual direction of travel. It will also raise and lower the tool if any particular angle change is greater than a specified amount so that you dont twist off or bend your tool. Less, of sheetcam fame created some sort of post or addition for either mach or sheetcam, its been so long i dont recall, but whatever it was improved the overall operation of the system 100%. Anyway im not really meaning to bore you with the explanation, and the original post is probably too old to still be valid. I just remember how extremely happy i was to see everything working exactly as i needed it to for once. so im reliving it for you