In making a pattern for a brass to fit in a semi-octagonal bed such as is employed in pillar-blocks, and sometimes in the small ends of connecting-rods and axle-boxes: after having made the bed of the brass to the same shape as the seat into which it beds, take off 1/16 inch in brasses below 3 inches bore, or 1/8 inch in brasses above that size, from the crown face of the brass pattern, for the following reasons: The casting of iron or of brass contracts, in cooling, most at the sides, and the above is to compensate for this contraction. Furthermore, it will require only 1/16 inch to be cut off the angles to let a brass (having bed-angles at 40°) down 1/8 inch on the crown; whereas it will require 1/8 inch taken off the crown face to let the bed-angles down 1/16 inch. A strict observance of this rule will, in all cases, save one half the time required to fit such brasses to their places. In brasses whose bed-angles are more acute, a greater allowance must be made.