I'm told that printers have paper cutting machines that can go through 500 sheets of paper
So they have no trouble going straight through the wrists of people holding the paper, leaving a lovely straight edge where their hands used to be. Nowadays they have sensors on them that check whether anyone is reaching into the machine, but they didn't always.

Warning: This story is on the internet, and is therefore completely unverified and unreliable!
(sabre-tooth monkey, Wed 4 Aug 2010, 14:42, 4 replies)

sabre-tooth monkey...
...I used to be a printer years ago and yes, these industrial guillotines do exactly what you say. The blades are a couple of metres long and are as sharp as fuck. The guillotines have a beam, that if broken, causes the blade to stop. To drop the blade through the paper you have to use two buttons (one for each hand) which are pushed at the exact same time to keep your hands out of harms way. The buttons are spaced as far as possible from each other.
Back in 1987 a popular brand of guillotine had a 'stop-use' order placed on it in the UK. There were reports of the blade re-descending (instead of stopping) when the safety beam was broken and the operator was reaching under the blade to remove the cut paper.

I'm a paramedic now and haven't been to any amputations from these machines, but I do remember a workmate losing both hands back in 1981. Must be a pun in there somewhere, but I can't think of it!
(emadex thinks the world will end on, Wed 4 Aug 2010, 15:13, closed)

"the saftey mechanism on this machine is really hard to work out - I'm stumped."
( Happy Phantom has been to Hastings, Brighton, and Eastbourne too, Wed 4 Aug 2010, 17:11, closed)

Same here...
Used to work in various finishing departments too.

The older guillotines (many years back) used to cut straight down (opposed to ones now that cut in diagonal fashion).
Other than giving a cleaner cut, safety improved too! The straight down action put so much force on the blade (look at the flywheel to see why.) that if anything enough to stop its full decent (knocking block), the blade would shatter!
(FunOnABun Smears lard on you!, Thu 5 Aug 2010, 8:38, closed)

I heard something similar from someone working in a printers
Also, the cutting machine's blade was only activated if you pressed 2 buttons simultaneously, each one a long way from the blade and the other button. So it forced you to have both hands out of the machine before it would cut the paper.
( le brian, Wed 4 Aug 2010, 15:14, closed)

I've got a couple of brake testers...
... specifically for testing guillotines and hydraulic presses. There's a sensor consisting of a motor, a spring like a tape measure and a bit of string which attaches to the chassis of the press and the actual moving part, and another actuator consisting of a motor and a shutter that breaks the beam. The idea is that you press a button and it waits for a moment then breaks the beam, and times how long it takes the blade to stop.

I don't actually test guillotines, I just picked these up when a calibration workshop was having a clearout and decided that they had too many nice 7-segment LED displays and counter chips to waste.
(gordonjcp, Wed 4 Aug 2010, 15:25, closed)

Yuck
I used to work with a guy whose brother had lost both forearms in exactly this kind of accident, though it was in a woodcutting situation rather than a paper place. His immediate reaction was to try to pick up his forearms. He committed suicide a couple of years later. Very sad. His brother - the guy I knew - never got over it.
(Smale is stuffed, Wed 4 Aug 2010, 15:57, closed)

This medium sized guillotine...
...gives you an idea of the blades' action. (This one is semi-automated though).
www.youtube.com/watch?v=o_vv5zZWOHU
(emadex thinks the world will end on, Wed 4 Aug 2010, 16:07, closed)

I'm not surprised
I never met someone who this had happened to, someone just casually told me about it while I was waiting for them to finish a cutting job for me. And that was 5 years ago or more, and it's still etched in my memory. It's a terrifying prospect. Sympathies to your friend, and his late brother.
(sabre-tooth monkey, Wed 4 Aug 2010, 16:16, closed)