A couple of years ago I created a 2-foot-wide county-by-county wood map of Oregon. Took for freakin’ EVER to get the files right, so I haven’t done any more. There are county maps available for free, in vector, but they need to be revised so a 1/8" bit can fit everything together. Recently I wanted to do Washington state in the same scale, but didn’t want to spend aaaaaallllll that time redrawing it county by county. So I messed around in Illustrator and found a set of path operations that will smooth everything out with minimal fussing. This technique works for any interlocking irregular shapes, like maps, and I thought I’d share the formula. This is specific to Illustrator but I’m sure Inkscape can do the same thing. This is for a 1/8" bit (1/16" radius of .0625"), for other bit sizes change the radius number to half the width of the target bit.
How to smooth out interlocking shapes for 1/8" bit in Illustrator:
- Get vector closed shapes (e.g. map elements like countries, states, counties, etc.) and size appropriately
- Select a closed path
- Path → Offset Path → -.0625" (note the minus sign) (also note, Joins should be set to “Round” and not “Miter”)
- Stroke 9pt
- Path → Outline Stroke
- Path → Offset Path → .0625" (no minus sign)
- Right Click object → Release Compound Path, Delete Inner Path
- Path → Offset Path → -.0625" (again with the minus)
- Delete intermediary shapes and select the smooth one
- Place the new smoothed shape in place
- There may be small gaps where corners come together, which can be manually edited with the pen tool
It took probably 8-10 hours to draw Oregon’s 36 counties by hand, making sure to keep the inner and outer radii large enough for the selected bit. With this new technique - and an Illustrator Action macro - I converted Washington state’s 39 counties and tweaked the minor gaps in about half an hour. (Puget Sound islands took most of the tweak time.)
Now, I haven’t actually routed out the Washington pieces yet, but they should work fine, based on my Oregon routing.
I’m mostly posting this here for when I forget how to do this in 2 years when I tackle California. Hope somebody else finds it useful as well.