GrblGru: Free CAM program with 3D simulation for mills and lathes

I am pleased that you have tried GrblGru. :slight_smile:

But I’m not sure if I’ve understood your question correctly.
Actually, you only need to drop the DXF file onto the graphics screen using drag & drop, for example. Then the max. diameter of the workpiece plus a little safety should automatically be displayed at the bottom left in the “Start diameter” input.
By clicking on the little up/down arrows of the input, the value changes and the green tool path is updated with a slight delay.

If this does not work, please save the project file and make it available to me here.
Then I can better understand the problem.

Please also download the current version V1.1 from my website

Thanks for the reply. I have had some time to use this more on PTO, and I think that my previous issue was due to user error.

One more question - is there a way to limit the max depth of cut when threading?

I am finding that the first few passes are a bit too deep for my setup, and have to increase the number of passes quite drastically to avoid stalling the stepper the first couple passes.

Thank you.