Projection welding is multi spot welding process. In resistance welding, the pressure is released after the weld cools. Grey cast iron is best welded by oxy-acetylene. The edge preparation for welding Is not needed up to 4 mm thickness of plate. The relation for cutting tool life is given by VTn = C where V is cutting speed, T is corresponding life n and C are constant depending on cutting conditions. The numerical value of n for roughing cut as compared to that for light cuts in mild steel does not on type of cut. A plug gauge is used to measure cylindrical bores. Aluminum has a higher cutting speed than cast iron & tool steel. A magnetic chuck is generally used when a large number of components are turned and parted off from a bar. Gear tooth vernier is used for measuring gear tooth profile. Undercutting is cutting from the base of a work-piece. Laser welding is widely used in electronic industry. Un- like materials or materials of different thickness can be butt welded by control of pressure and current. In are welding operations the current value is decided by the size of the electrode. The phenomenon of weld decay takes place in stainless steel. Arc below takes place in welding stainless steel. Swab is used in foundry for repairing the mould.