The accident happened on last Thursday at a meat processing plant in San Luis Obispo.
The machine's blades "came around and broke his arm and came around again and broke his arm a little further up the next turnaround," San Luis Obispo Fire Battalion Chief Neal Berryman said.
Berryman said the man's head or neck would have been hit next.
The man's screaming alerted his co-worker, who saw the victim's legs protruding from the machine and switched it off in the nick of time.
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A picture taken by a firefighter shows the man entangled in the machine up to his waist -- his legs pointed upward, with rescuers on all sides.
Hydraulic tools had to be used to pull the blades apart and free the man, KEYT, a CNN affiliate quoted fire officials as saying.
The man was taken to a local hospital, where he was treated for a broken arm.