Sage words of advice from a friend who is currently sitting in ICU hoping that the surgery to re-attach his thumb takes (the first one didn't).
He was using a power miter saw to slice off a piece of aluminum. The saw snagged the work piece and twisted it sending his thumb through the blade before he knew what happened.
Thank $DIETY for modern medicine that makes even attempting to reattach a severed digit. Seems not very long ago Dr's wouldn't have even tried.
"Always clamp the work!"