2 mechanics were reinstalling a plant crusher accumulator. The part had 3 sheared bolts and broken seal causing a hyd oil leak. EE was lifting the part back into position by hand while waiting for the hyd jack to hold it in place. Accumulator got in a bind with the support clamp and fell back to the deck smashing EE's left middle finger. EE was wearing gloves. Part weighs 30-40lbs.