This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.
Mark out the length and depth of the elbow, ABCD; draw a semicircle at each end, as from AB and CD; divide each semicircle into eight parts; draw horizontal lines as shown from 1 to 1, 2 to 2, etc.; divide the circumference or length, ACBD, into sixteen equal parts, and draw perpendicular lines as in figure; draw a line from a to b and from b to c, and on the opposite side from d to e and e to f for the top sweep set the dividers on fourth line from top and sweep two of the spaces; the same at the corner; on space for the remaining sweeps set the dividers so to intersect in the three corners of the spaces marked X. The seams must be added to drawing.
[Another Method for describing a Straight Elbow.] FlGS. 9 & 10.
Fig. 9. - Draw a profile of half of the elbow wanted, and mark a semicircle on the line representing the diameter, divide the semi-circle into six equal parts, draw perpendicular lines from each division on the circle to the angle line as on figure.
Fig. 10. Draw the circumference and depth of elbow wanted, and divide into twelve equal parts, mark the height of perpendicular lines of Fig. 9 on Fig. 10 a b c etc.; set your dividers the same as for the semicircle and sweep from e to e intersecting with f and the same from a to the corner, then set the dividers one-third the circumference and sweep from e to d each side, and from a to b each side at bottom; then set your dividers three-fourths of the circumference and sweep from c to d each side on top, and from c to b at bottom, and you obtain a more correct pattern than is generally used. Allow for the lap or seam outside of your drawing, and lay out the elbow deep enough to put together by swedge or machine. Be careful in dividing and marking out, and the large end will be true without trimming. The seams must be added to drawing.
To Joint Lead Pipes. - Widen out the end of one pipe with a taper wood drift, and Scrape it clean inside; scrape the end of the other pipe outside a little tapered, and insert it in the former; then solder it with common lead solder as before described; or if required to be strong, rub a little tallow over, and cover the joint with a ball of incited lead, holding a cloth (2 or 3 plies of greased bed-tick) on the under side; and smoothing over with it and the plumber's iron.