Nick,
"ONSRUD 52-910 1/4" Solid Carbide Two Flute Upcut Extra Heavy Duty for Woods and Composite Woods"
Not quite sure what the "Extra Heavy Duty" implies for geometry and don't cut much Ply or any Poplar, but my 2 similar 2F .25" center cutting ups in hardwoods like higher rpm than yours. For a simple/long rectangular cut out with .5"R corners 20X5" for instance with 1/2D passes in Hard Maple one gives best finish at 1.6IPS,10K, and the other at 2.2,14K. Go figure.
Are you using 3D tabs and can you put a very small radius on corners? Helps quite a bit, as machine never has to come to a complete stop.
Agree with Dave that changing VR settings after reading Brady's article will probably help (need to start playing with that myself for small complex shapes and just getting into 3D), but still using default VR settings myself.
Don't like that"sounds like metal on metal". Can you post a vid?
Is bit dull or are there complex shapes involved? Are you getting good edge quality at those rpm's?
scott P.
2013 Desktop/spindle/VCP 12.0*
Maine