Carbide Create does not offer rest machining at this time — it’s a frequently requested feature though.
with ball endmills, that is likely complicated and the “ridges” of the ball means you likely rest machine EVERYTHING
I still think the 2 pass makes no sense; I would rather pick a stronger bit (tapered end mill) and just do it once instead… (there seem to be people who don’t even do roughing once they use a strong enough tapered endmill… I’m not that brave yet)
Thank you for the advice on test cuts, I ended up with a 3D roughing pass at 1/8 stepover, 1/16 depth of cut, 200in feed rate. WAY faster than what I was going to originally use.
I’m pretty sure it could have gone even faster, but it was at this rate the sweepy started having problems. I was getting a series of one to two inch long sticks that were collectively getting stuck within the sweepy. It was only happening when there were long X axis passes, and the alternating plywood grain was also running the same direction.
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Thank you for the advice. Today I finished the roughing pass, and the first finishing pass with the 1/4 ball. After watching it run today I agree that multiple finishing passes is probably not needed. I could have jumped right to the 1/16 ball finishing pass.
However this has turned into an interesting experiment. This weekend I am going to do another finishing pass, but skip straight to the 1/16 ball and I am going to run that with the 90 angle option.
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What stepover are you planning for?
@ColdCoffee, this project screams for lasering things onto it, @ClayJar style?
[nerdy sidetrack: to this day Skyrim is the only video game where I remember doing contemplative walks in the wild for hours, amazed at what those developers had accomplished. I read somewhere that the next one is still years away, and a few days ago Microsoft bought Bethesda, and that felt like taking an arrow in the knee]
Regarding how to finish this piece, I’m on team tapered endmill. You can run them crazy fast (relative to their size) in a situation like this.
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For the 1/16 ball I am using a 10% stepover so .00625 which means it will take awhile. However since this is the second finishing pass there won’t be much material removed so I am going to leave the dust collection off, and probably be brave enough to not remain in the garage the entire time.
I am going to get some tapered endmills, but I want to finish this project this weekend so I am going to continue with the standard 1/16 ball.
So far everyone that has seen the two maps in person has suggested another project for me. So it looks like I have several topographic maps on my to-do list, the tapered endmills will get a workout.
Sadly, I had to pull the plug on this attempt. Had multiple problems, the final blow appeared to be a bit slipping or some other z axis problem. The 1/16 ball started milling about 1mm lower than it should have right down the center of the map.
I’m going to start over, reduce some of the detail (roads between towns) and try again with the tapered 1/4 inch shaft bits. At this point I’m going to try and avoid 1/8 shaft bits in the Shapeoko. I have not owned the Shapeoko long enough to draw any definite conclusions other than I’m having bad luck with 1/8 bits slipping.
you shouldn’t need to reduce detail at all…
also may I suggest starting with something a little smaller in size, maybe 4"x4" or so… just to get to the end of it and ensure all your settings are sound/working/etc
Looks like you have got a lot of great advise on cutting. My one suggestion is to consider using a different material. Baltic Birch can be from great to not so great in quality. There can still be voids in the subsurface of the plys. Even in Baltic Birch or Finnish Birch there can be knots in the middle plys. If you hit a void it could ruin all your work. MDF could work but solid wood might be better even if it is just clear pine with glued up boards.
With all this work you dont wont to find out you got a bad batch of baltic birch plus the glue on the plys can fail when getting to fine detail like the top of a mountain.
Also check out HDU Material at https://www.curbellplastics.com/Shop-Materials/Specialty-Products/Prototyping-and-Tooling/High-Density-Urethane-(HDU)-Boards/High-Density-Urethane-(HDU)-Boards#?Shape=CRBL.SkuToolingBoard
and check out https://precisionboard.com/tooling/topographical-map-time-study/ for reference.
FYI
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I got my Baltic-Birch from WoodCraft, and (so far) that is the only option I found to locally source “good” plywood. I paid $50 for a 48in x 30in x .7in board, and yes it has roughly 4 to 5 knots on every inside layer 
I need to find a local source, like what John Clark found near him.
Started my 2nd attempt, and things are going well so far.
For the finishing pass I am going to use a tapered ball nose bit that @fenrus suggested.
I reduced the detail in the 3D model (it no longer has the city platforms or roads). I am adding that detail back via (non 3D) toolpaths after the finsihing pass is done.
I’m not sure when @robgrz added this feature, but being able to see the X,Y and especially the Z height in a 3D model REALLY made this possible. If you have not noticed that information down in the corner…
I am also going to stain the board between these two steps so that detail pops out more. Like what I did with the last topographic map.
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Looking forward to see how this is turning out using the tapered ball nose.
I really like this as well. I find that it helps me visualize how the final product is going to turn out.
Status Update: Temporary Delay
With all of the complicated things that could have gone wrong, I just simply dropped my 1/16 down-cut bit and it broke against the garage floor
Up until that point, things were going great. The topographic carving is done, the board has been stained, some post stain details have been added… and now I wait for a replacement bit to arrive.
The 1/16 downcut will be used to add the roads, logo and about 200 small dots for landmarks.
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Bummer about the bit 
But love that map
Like an arrow to the knee.
Edit: I dropped the first 1/32" AND 1/16" bits I ever took out of the packaging to use, within minutes of each other. Felt like quite a monkey that day.
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that is looking awesome already
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