Page:Sheet Metal Drafting.djvu/194

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180
SHEET METAL DRAFTING

Problem 43
FACE MITERS

81. Face Miters.—A face miter may always be distinguished from a return miter by the fact that the miter line can be seen in the elevation; whereas, the miter line of a return miter always appears in the plan.

Figure 255 gives the same profile as was used in Fig. 245. This profile is used again in order to afford the student an opportunity to compare the two types of miters and note wherein the difference lies.

The ogee is divided into small spaces and numbers placed at each point of the entire profile.

Extension lines are carried over to the right from points 1 and 11 to form the outline of one leg of the miter. These lines are then intersected by a miter line drawn at an angle of 45° since the miter itself is a square, or 90° face miter. The other leg of the miter is now drawn and lines added to complete the elevation as shown by Fig. 256.

A line of stretchout, Fig. 257, is next drawn and the distances between points of the profile transferred in their proper sequence, with numbers to correspond. Measuring lines are drawn through each of these points at right angles to the line of stretchout. Starting from point 1 of the profile an extension line is carried to measuring line 1 of the stretchout. In like manner all other points of intersection are located in the stretchout. Any tendency to "short-circuit" this operation should be guarded against by referring back each time to the starting point in the profile. By neglecting to do this, mistakes are apt to occur, which can be detected only after the parts are formed up and the assembling process has begun. The miter cut of the pattern should now be drawn in, and dots placed on the lines that are to be bent in the cornice brake.

As was the case with the square return miter, the pattern can be taken directly from the profile. The main consideration is the proper placing of the profile with reference to the direction in which the extension lines from the profile are to be drawn. A mistake of this nature will result in a face miter when a return miter was intended; or, a return miter when a face miter was desired. Also, as was the case of the return miter, the extension lines can be taken