I need to precise route cut into a plastic shell. The plastic is ABS and is about 3/8" thick. I need my route to just barely penetrate the shell, or just barely fall short of penetrating so I can finish off the cut by hand. The key thing is we don't want to cut up the objects that are behind the shell (batteries).
What portable handheld tools would let me dial in the depth of a route to
1/32" precision? The width of the route channel doesn't matter for this application.
Is the plastic shell completely flat or rounded? If it's not completely flat, then you've got some difficulties.
You could use a Dremel type tool and grind it away. The problem with using any router type tool is that using it handheld, you're not going to be as accurate as you want and face the possibility of your hand slipping and cutting right through the shell.
My best advice would be the Dremel and you sneaking up on the depth you want to cut to.
Dremel sell a "tile cutting" jig that's a small support collar for use as a router. It's a very useful gadget.
I'd do through cuts, as these are easier to cut (no worries from the bottom) and in particular they reduce the heat generated when cutting, thus avoiding some of the swarf-welding trouble. Leave "postage stamp" joiners in the cut-line, until you're ready to break it all free.
Laminate trimmer?
Have you considered a hot knife? Melts the plastic and doesn't need a sharp edge so won't cut into the batteries unless they are plastic. You can get a kit for under 20 bucks from Sears or get the cheapest soldering iron you can find and pound the tip flat with a hammer. You can control the depth by grinding or filing the tip to the shape you need.
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