PITTSBURGH (AP) _ A man whose hands were severed and crushed in a paper mill accident was in guarded condition today after surgeons rebuilt one hand with parts from both, hospital officials said.

Dr. Marc Liang, a surgeon at Allegheny General Hospital, said Sunday chances are excellent that Daniel Hershberger's new left hand will be useable. The hand was built with three fingers from Hershberger's right hand and the thumb and palm on his left.

''His fingers are pink, warm and well vascularized in his now reconstructed left hand,'' Liang said. ''It looks good now.''

Hershberger, 25, of Martinsburg, lost his hands Friday morning when they became trapped in a paper pulp machine he was installing at the Appleton Paper Plant in Roaring Springs.

He flown by helicopter to Allegheny General, where doctors worked for 18 hours to rebuild the left hand.

The palm of Harshberger's right hand was crushed beyond restoration, doctors said.

Dr. Glenn A. Buterbaugh, head of Allegheny General's replantation team, said he believes the construction of a new hand, using parts from another that cannont be saved, had not been done before in an emergency situation.