Thimble is a part of fusion welding of rail joints. It is fitted from inside at the lower part of the crucible. It enables the tapping of molten metal into the fusion weld area (mould fitted with rail joints gap). It is in cylindrical shape with hole in centre. The hole in this thimble is plugged with a closing pin and asbestos wool. Its dia. 18-20 mm for 25 mm gap technique and 20-22 mm for 75 mm gap technique.
It controls the flow of molten metal into the welding mould.
