MecSoft Corporation

Rhino 4.0 SR9; RhinoCAM 3.0.0.48; working in millimeters.

Doing 2-axis engraving.

When I reduce the cut feed in RhinoCAM, l can read the .nc file and see the cut speed as Fwhatever.

But when I reduce the feed down to 20, all of a sudden the .nc file just gives me F25.4

I see that the "toolpath" from RhinoCAM does not contain feeds and speeds at all.
So it must be that the feeds and speeds are handed to the post processor separately from the
toolpath. And so whatever weird behavior I'm seeing in feed speed, it's the fault of the post processor,
and I need to go to the guys who made the post-processor to fix it.

Is this correct?

From your description it looks like the low value for feedrate in your post processor is set to 25.4. You can edit the post processor from the program tab, select Feedrate tab and set the low value to less than 20. Save and close the post processor before post processing the machining operation.