. Sheet metal workers' manual; a complete, practical instruction book on the sheet metal industry, machinery and tools, and related subjects, including the oxy-acetylen welding and cutting process . stum of a right cone, which canbe developed by the radial method. If the time is limited and only a few pieces are re-quired, there are several short methods which can be ap-plied to the same purpose. An approximate pattern de-veloped by one of the short methods in common use isshown in C, Figure 174, and may be produced as follows:Draw a center line as AB and on it fix a convenient pointe. With th
. Sheet metal workers' manual; a complete, practical instruction book on the sheet metal industry, machinery and tools, and related subjects, including the oxy-acetylen welding and cutting process . stum of a right cone, which canbe developed by the radial method. If the time is limited and only a few pieces are re-quired, there are several short methods which can be ap-plied to the same purpose. An approximate pattern de-veloped by one of the short methods in common use isshown in C, Figure 174, and may be produced as follows:Draw a center line as AB and on it fix a convenient pointe. With the compasses set to a radius equal to ed in theelevation A, scribe the arc dbd; starting from the point bspace off a distance dd on each side equal to one-half thecircumference of the top of the measure, as shown by thefigures 1 to 9 in the half-section in the elevation. Drawa line from e extended through d, and place the width ofthe back of the lip as shown from d to c. Now take thedistance of the front of the lip db and place it as shown SHEET METAL WORK AND PATTERN DRAFTING 205 from b to a. Draw a line from c to a and bisect it to ob-tain the center point m. From m at right angles to ca, A. Figure 174.—Plan of Measure with Flaring Lip, and Patterns for Lip. draw a line intersecting the center line AB at n. Thenwith n as center and nc as radius, describe the arc cac,which will complete the net pattern for the lip. Add an 206 SHEET METAL WORKERS MANUAL allowance for a lap seam on the end, and a Vs-n^h edgefor a single hem on the top. After this edge has beenturned in the burring machine (Figure 47) the lip isplaced on a flat stake and the edge closed down by meansof the mallet. Then the lip is formed on the blowhornstake, placed in position on the top of the measure, andsoldered on the inside. Lips for measures of large diame-ter are usually wired at the top edge, and the allowance,for wire is made in the usual manner. Another style of lip is shown by abgh in elevation, andin
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