Table 99.-MULTIPLIERS FOR CONVERTING CUBIC INCHES INTO LBS. Measuring Patterns.—In order to provide against running castings short of metal, moulders in measuring patterns allow 2 lbs. per foot for straining, &c., and take the weight of 1 square foot of cast-iron 1 inch thick at 40 lbs., or 5 lbs. per superficial foot for every 4th of an inch thickness of metal. Hence the rule to find the weight in lbs. is-multiply the length in feet by the breadth in feet, and by 5, and by the number of ths of an inch the metal is thick. In measuring cores, the same rule is used, but instead of multiplying by 5, multiply by 4'7, because 40 lbs. per square foot 1 inch thick, is too much to take out for cores. Table 100.-DECIMAL APPROXIMATIONS, ETC. Cylindrical inches multiplied by 0004545 cubic feet. Cylindrical inches multiplied by 2049 lbs. of cast iron. ditto 22069 = Ditto Ditto ditto 2179 *207 =lbs. of tin. 2042 lbs. of zinc. lbs. of copper. =lbs. of lead. 2385 lbs. of brass. Table 101.--MULTIPLIERS FOR CONVERTING THE WEIGHT OF ONE METAL TO THAT OF ANOTHER. = Examples of the use of this table.-Example 1: a wrought-iron shaft-forging weighs 3 cwts., required the weight of a Metal Plates.-The weights of metal plates are given at pages 282, 289–292. 300. A solid pattern, without cores, weighing 1 lb., made of yellow pine, will weigh, when cast in cast iron, 16 lbs.; in zinc, 15.8 lbs. ; in tin, 16 lbs.; in steel, 17:02 lbs.; in brass, 18.8 lbs.; in gun metal, 19 lbs. ; in copper, 19.3 lbs.; in lead, 24 lbs. The Cone. To find the solidity or cubic contents of a cone: multiply the area of the base by one-third of the perpendicular height. To find the convex surface of a cone, multiply the circumference of the base by one half the slant height; to which add the area of the base for the whole surface. To find the surface of the frustrum of a cone: multiply the sum of the perimeters of the two ends by half the slant height, and add the areas of the ends. To find the cubic contents of a frustrum of a cone, add together the areas of the two ends and the mean proportional between them (that is, the square root of their product), and multiply the sum by one-third of the perpendicular height. To find the cubic contents of a wedge: to twice the length of the base add the length of the edge; multiply the sum by the breadth of base, and by one-sixth of the height. To find the surface of a sphere or ball: multiply the square of the diameter by 3'1416. To find the cubic contents of a sphere: multiply the cube of the diameter by '5236. To find the surface of a segment of a sphere: multiply the diameter of the sphere by 3'1416, and then by the height of segment. To find the cubic contents of the segment of a sphere: from three times the diameter of the sphere, subtract twice the height of segment, then multiply the difference, by the square of the height and by 5236. To find the surface of a cylinder: multiply the circumference by the length for the convex surface, to which add twice the area of one end, for its whole surface. To find the cubic contents of a cylinder: multiply the area of one end by the length. To find the cubic contents of a parallelopiped: multiply the length by the breadth, and multiply that product by the depth. To find the surface of a parallelopiped: add the depth to the breadth and multiply by the length, to which add the area of the end. To find the area of a ring included between the circumference of two concentric circles: multiply the sum of the diameters, by their difference, and by 7854. Strength of Cast Iron Pillars or Columns.-The following are Mr. Gordon's rules for columns: W = the breaking weight in tons; A, the sectional area of the material in inches; R, the ratio of the length to the diameter, the least diameter of the section being taken. Table 102.-SAFE LOAD ON HOLLOW CAST-IRON PILLARS. The Loads given in the Table, are for hollow cast iron pillars with flat ends, and securely fixed. Hollow columns fail principally from crushing, when the length does not exceed thirty times the diameter. Columns with both ends round are only 3rd, and columns with one end flat, and the other end round only rds, the strength of columns with both ends flat. The strength of a column of a cruciform section is only, and of a double flanged section only, that of a round hollow column, of equal weight. 32 In contracts for columns, a variation of from to inch in the thickness of metal is permitted in most cases. Table 103.-PROPORTIONS OF RIVETS AND OF SINGLE AND DOUBLERIVETED JOINTS FOR WROUGHT-IRON PLATES. In Zigzag Riveting, the rivets in one line divide the spaces between the rivets in the other line, as shown in Fig. 141, page 178. The distance between the rivet-hole and the edge of the plate, or between two rivet-holes, should never be less than the diameter of the rivet. Proportions of Rivets.-A pan-shaped rivet-head should equal in diameter 1, and in thickness the diameter of rivet; and when a cup or snap shape, the diameter of rivet head should equal 14, and the depth the diameter of rivet. The diameter of a conical rivet-head should equal twice, and the depth the diameter of the rivet. The diameter of the head of a countersunk rivet should equal 1 times, and the thickness the diameter of the rivet. The length of rivet required to form the rivet-head is equal to the diameter of the rivet for countersunk heads, and to 1 times the diameter for cup and conical rivet-heads. All Rivet Holes should be perfectly fair with each other, those that are not fair should be rhymed out until they become so-drifting should not be permitted. The rivets should completely fill the holes-which should be slightly countersunk under the rivet-heads, and the rivet-heads should be true and central. When the rivet holes are drilled in "place" the plates should be taken apart and the burr removed, as it prevents the plates closing tightly to make a good joint. The Edges of the Plates--in best work-should be planed to an |