A crew of employees was performing workover services. The crew was attempting to break out a crossover sub, on top of the casing scraper, using tongs. The employee was using a 36-inch wrench on top of the tongs. The tong operator engaged the tong before the employee removed his hand. The tong pinched the employee's finger between the tong and the wrench. The employee lost the fingertip of his right middle finger.