EE was assisting 3 others remove a shaft from a Mac 12 mantrip. They had one side of the shaft suspended in the air approx 26 off the mantrip with a pair of come-alongs. The IE grabbed the bearing end of the shaft to lift it over the rail of mantrip. Another EE continued to crank the come-along causing the shaft to shift, catching his middle/index fingers between trip and shaft.