Bad luck with drifts.
An acquaintance of mine lost a finger the other day while doing some undercarriage work on an excavator. I don’t know any details other than the finger was re-attached but I have a suspicion that it was something similar to a close call of my own:
Once, during my welding apprenticeship, I broke two fingers while servicing an excavator. I was driving a track pin and missed the drift. What brought my 16 pound hammer to a stop was my hand coming between the handle and the edge of a track pad.
The journeyman I worked under had nearly lost a finger doing the same thing many years ago.
There might be something to be said about making a pin press.