Round columns are usually moulded from a split pattern which is constructed as described in connection with Fig. 66 of of "Pattern Making." The pattern is made of the maximum length of column to be cant. Loose flanges are used to limit the length of the pattern. The cope and dreg have semi-circular holes or spaces cut out of their respective connecting edges to allow the excess length of pattern to project beyond them. As round columns are almost always solid in the shell, dry sand or loam cores are used. These cores are built about a perforated iron pipe which serves to carry off the gases.
Gear Moulding may be done from either full or partial patterns. When done with full patterns, the work is identical with that of the simpler castings that have been so fully described. They are laid on the moulding board and the drag and cope rammed in the regular sequence.