Hello Stephen,
Rest machining is a little odd in F360 (compared to other CAM packages I have used.)
It does not know or try to figure out how much stock is left on a model. It assumes every cutter mills to finish size.
So I see you added the previous cutter diameter and the ‘stock to leave’ together to get the diameter you entered in rest machining - 1.375" with no corner radius. And I know you want .125" left on the wall for the 1/4" endmill to finish. Unfortunately this trick does not help at all in this case.
F360 thinks you actually took a 1.375" diameter cutter and cut right to finish size against the wall. Since your wall on this piece is wide open ( no other intersecting walls ) F360 thinks the 1.375" dia. cutter finished it - so nothing left for the next cutter to do. That is why it will not generate a toolpath with the 1/4" endmill.
F360 does not know what your previous tool diam. was. It just goes by what you type in to the ‘Rest Machining’ box. For this reason I only use rest machining when nothing else will do it.
You could set the ‘Rest Machining’ corner radius to something like .250", a 1.375" dia. cutter with a .250" bottom rad cannot finish that wall. That’s why this trick works. If you try it you will see that does work but it does not really do what you want.
Better is to use ‘2D Contour’ toolpath and leave “Rest Machining” off. Hold down the ‘Alt’ key and select all the top edges of the wall. Turn on ‘Roughing Passes’ under the 'Passes" tab. Enter something like .06" in 'Maximum Stepover" box and 2 in “Number of Stepovers” box. When you turn on “Roughing Passes” a new option appears in the list above it called “Stepover”. This is the finish pass stepover ( I wish they would have named it that ). Set that stepover to something like .010"
The 1/4" endmill will then make a pass .070" away, then another .010" away, then the finish pass. Have a look at the attached I have modified:
BLANK 2 v2 better rest finishing.f3d (91.2 KB)