In my experience the only time a single flute can be used on smaller hand held router with little to no vibration is the O flute design in the 1/8" size(1/4" is pushing it) and used on soft wood or plastic.
I have some 1/2" single flute combination bits and boy they act weird, The only router I can use them on is my huge Festool OF 2200, all the other router just vibrate too much using the larger single flute bits. I won't buy anymore 1/2" regular single flute ever again though, but they do work nice enough with the big router(still feel weird and sound even worse).
Now on a CNC it doesn't matter the single flute work great, but for hand, held especially for newbs, I would never suggest a single flute larger than 1/4"(try to stick to 1/8"). Even then try to stick to those O flute versions. With CNC the single O flute work great in almost any size on many materials, even on aluminum.
Last edited by dovetail_65; 10-16-2017 at 10:12 PM.