Fixture Mounted Spot Welding Bolt Welding SPM. This Semi Automatic Welding Machine has Fixture Mounted Welding Guns and Projection welding Machine. The operator only loads the component and the machine spot welds and projection welds the bolts automatically. The machine has complete Poka Yoke (mistake proofing)system for Bolt sensing, nut sensing and part sensing to avoid weld failures and part missing