for a better blade, use this one https://www.thingiverse.com/thing:3467328 its better and more stable.
a ~5.5 inch blade that you can put a standard Lego x-pipe through the middle and can be spun.
Features: 2 spikes, 4 supports, good printing, good strength, crappy balance when being balanced on an x-pipe. it wobbles but evens out at high speeds.
Disclaimer: the Lego Bot(AfterShock) in the pictures is not included.
Filament doesn't matter, but use a strong kind, like
use the strongest filament you have(we have made with PET and works well, but carbon fiber would be a fun build.) remember to use protective eyewear when spinning at full speed.
wanted a cooler weapon for my bot. fun print and can break through plastic if spinning fast enough.
My Lego Bot. please wait, it is a little slow when loading.