Jesse James cuts off finger in machine shop

It should be self-explanatory -- but if you're too squeamish to click, Jesse cut off the tip of his right pinky. Right under the nail. It's real gnarly, so click at your own risk.

He posted the photo on his Instagram, along with the caption, "Doesn't look like this little dude's gonna make it, Nice know'n you little buddy."

As for what happened -- Jesse called in to TMZ Live moments ago, explaining he was working a machine at his shop in Texas ... and had a little accident (no kidding).

He wasn't too concerned though ... he called on his way to surgery sounding like it was just another Tuesday. Pretty badass.