Ellsworth M. Longfield

“ The practice of assuming a section, common to some drafting rooms, results in a more or less distorted fitting, according to the experience the draftsman has had in designing such fittings. The workman in forming and assembling the fitting has difficulty in that he must compel the assembly to take an unnatural shape.
The plan, Fig. 301, is first drawn according to the dimensions taken at the job. The profiles are then divided into the same number of equal spaces. After the order of triangulation has been determined, base lines are carried to the corners M and N of the rectangle. ”

“ In drawing this view, care must be taken to get the miter lines at the correct angle for a two-piece 45° elbow. The half-profiles are then drawn in their relative positions and divided into equal parts. It has been observed that in treating oval profiles the straight sides of the oval are never divided. The divisions of the curved portions are numbered and lettered and extension fines carried from each division to the miter lines. ”

“ This is intersected by an arc drawn from point 1 with a radius equal to line 1-2 of the true section. Fig. 296. This establishes point 2. With point 2 as a center and a radius equal to the upper base of section 2 to B, an arc is drawn bearing away from point A. This is intersected by an arc drawn from point A with a radius equal to distance AB of the true section, Fig. 296, thereby establishing point B. In this manner all of the points of the pattern are fixed and the curved and straight lines of the pattern drawn in. ”