While sorting old metalworking books, I came across a photo in an old
school textbook that showed a large press frame being milled with an
endmill (yes, it was a true endmill) in a horizontal mill of some sort.
The endmill was about 10" diameter (as big across as the operator's
head) and at least 2 feet long, spiral flute.

It kinda got me thinking about the largest actual cutting toolbits that
have ever been used. There was a discussion a while back about the
largest single block of steel people had ever seen...what about the
largest tooling (not machine) used to cut these kind of things?

Koz