This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.

The width of sheet required to form a cylinder is ascertained by multiplying the desired diameter of the cylinder by 3.1416; the diameter of a cylinder made from a sheet of known width will be the product of that width multiplied by 0.31831.

Among the most frequent operations in sheet-metal working is the adjustment of cylindrical pipes to each other at various angles, and in various positions.

If it be desired to join 2 pipes of equal diameter at right angles to each other, proceed as in Figs. 179, 180. The T-piece a will fit the outline of the main pipe b, as shown. To strike out this T-piece, take a sheet having the same width as the distance between c d, and the same length as the circumference of the T-piece. Divide the circumference into halves by the line e; then draw the line f at the level of the contact line of the main pipe b; finally describe 2 curves g commencing at the point h on the line e, touching the line f, and terminating at the points c. These curves g must be sketched in, as they do not form correct arcs of a circle, but are somewhat deeper. The seam joining the edges c d will be on one of the long sides of the T-piece. The exact delineation of the curve g may be attained by dividing the half-circumference into a number of equidistant spaces by vertical lines, which are numbered or lettered; equivalent lines then drawn at the same distances and of the same lengths on the sheet, indicate the sweep of the curve.

For small operations, the tools required may be said to consist simply of a mallet, shears, and a few shapes for moulding on; but many useful little machines have been introduced into the trade, and effect considerable saving in labour. The ordinary boxwood tinmen's mallet should have the paul rounding at one end and flat at the other. Tinmen's pliers are shown in Fig. 181.

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