The Forklift Operator needed to switch the fork for a boom attachment to complete a task but couldn’t remove the fork because the connecting bolt between the Forklift Pin and the Hydraulic piston had broken. As a result, the Forklift Pin became disconnected from the Hydraulic piston. Additionally, a fragment of the broken bolt became lodged within the Forklift Pin, causing it to jam inside the frame. The Forklift Operator reported this issue to the Chief Mechanic, who inspected the Forklift and asked the Forklift Operator to wait, as the Chief Mechanic was busy with the generator. Despite the Chief Mechanics instruction to wait, the Forklift Operator and the Welder (Sub-contractor) agreed to remove the pin from the Forklift frame. The Welder placed an external bolt inside the Forklift frame so that he could use hammer to drive the pin outside of the Forklift frame. As the Welder inserted the external bolt inside the frame, the Hydraulic Piston was engaged by the Forklift Operator and the Welder's right hand got trapped between the bolt and the Forklift frame. This resulted in a crush injury to his right thumb and index finger