I’m cutting 12mm Baltic Birch plywood with a 1/8" bit using a Harbor Freight trim router. I have finished a few parts at 1mm depth per pass. Can I safely increase this? Is there a chart or reference for feed rates, depth per pass, etc?
Not really. Every machine is different. Use a scrap piece of material and try different depths. Try to keep the depths as even divisions of your total depth, you might need to slow the speed down, but if you can do it in 2 or 3 passes, it’s still faster than 12 passes at a slightly faster feed. Baltic birch cuts pretty well though, I’d think you shouldn’t have any issues with a 3 or 4mm depth of cut.