This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The top and bottom of all cast-iron columns should be turned off in a lathe to insure a bearing at right angles to the axis, and plates should be used to increase the bearing. These plates are cast with a ring or with projections to hold the column in place against movement, and they should be planed to a perfectly even bearing. The cap must never be spread out as a casting, Fig. 174, but should carry up the line of the column itself, all ornamentation requiring a great projection being cast separately and fastened on, as in Fig. 175. This allows the shaft of the column to run straight up to bear the weight of the column above, while the girder is borne by the projections cast upon the column. The distance from the cap to the top of the column should be about four inches greater than the depth of the girder to allow room for bolting the columns together.
Fig. 171. Improper Casting of Column.
Fig. 175. Proper Application of Ornament.
With a wooden girder, the ends of the timber must be cut out to fit the diameter of the column (Fig. 176), and the girders must be tied across the cap by stout straps on each side. If steel beams are used, they can be tapped to the column plate or strapped together around the column.