. Canadian Shipping and Marine Engineering January-December 1916. necessitate one ofthe courses to be slightly opened outwith a machine suitable for that pur-pose, or, in default, with a hammer, sothat one course will fit over the other. In tinsmith work suitable seamingallowances are made according to thestyle of seaming. Fig. 2 shows the pat-tern without any allowance for laps. 60-Degree Elbow Fig. 3 shows the elevation and half-sectional views of a two-course cylindri-cal 60-degree elbow. Draw the line GLO,make OL equal to 11/16 inches, and theneutral diameter of the elbow GL equalto IV2 in
. Canadian Shipping and Marine Engineering January-December 1916. necessitate one ofthe courses to be slightly opened outwith a machine suitable for that pur-pose, or, in default, with a hammer, sothat one course will fit over the other. In tinsmith work suitable seamingallowances are made according to thestyle of seaming. Fig. 2 shows the pat-tern without any allowance for laps. 60-Degree Elbow Fig. 3 shows the elevation and half-sectional views of a two-course cylindri-cal 60-degree elbow. Draw the line GLO,make OL equal to 11/16 inches, and theneutral diameter of the elbow GL equalto IV2 inches. With centre 0 and radiusG, describe the arc GI. With the sameradius and G as centre describe anotherarc to intersect arc GI at I. Connect Ito 0 by a straight line. The angle formed by GO and 10 is60 degrees. Bisect the arc GI at M, andthrough this point draw a straight linefrom 0, extending to H. At right anglesto GL draw the lines GH and LK to in-tersect the mitre line HK. Connect H toI and K to J. If carefully constructedthe course GHKL will be equal to. the line FAF, and parallel to the centreline AB. Set the dividers to the distanceVt1, Fig. 1; transfer this over to thecorresponding number in Fig. 2. It willbe noted the seam is located on the line1*11 Yig. 1. Reset the dividers in each case to thedistances 4?4}, 323\ 222\ l*ll, Fig. 1, and transfer over each distanceto its allocated line in Fig. 2. 59 HIJK. Bisect GL at 4* and draw in thehalf-sectional view G4L. Divide thissemi-circle into any number of equalparts, according to the exigencies of thework. Project these located points tothe mitre line, as explained in Fig. 1. The stretchout LGL, Fig. 4, equalsIV2 times , which equals inches,or slightly less than 4% inches. Bisectthis line LGL at 7° and erect the perpen-dicular 7°71, thus locating the centre line MARINE ENGINEERING OF CANADA of the templet, and also defining- theseam lines ll1 and 1°1K Divide IT and7*7° each into the same number of equalspac
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