An Introduction to Machine Drawing and Design. David Allan Low

inch thick. All other dimensions must be deduced from the table for single riveted lap joints.

      

      Exercise 8.—The connection of three plates by single riveted lap joints is shown in fig. 6. To make the joint close one plate has a portion of its edge thinned out, and the plate above it is set up at this part so as to lie close to the former.

      Draw the three views shown in fig. 6 to the same scale as the last exercise.

      The plates are ⁷⁄₁₆ inch thick. All other dimensions to be obtained from table for single riveted lap joints.

      Exercise 9: Corner of Wrought-iron Tank.—This exercise is to illustrate the connection of plates which are at right angles to one another by means of angle irons. Fig. 7 is a plan and elevation of the corner of a wrought-iron tank. The sides of the tank are riveted to a vertical angle iron, the cross section of which is clearly shown in the plan. Another angle iron of the same dimensions is used in the same way to connect the sides with the bottom. The sides do not come quite up to the corner of the vertical angle iron, excepting at the bottom where the horizontal angle iron comes in. At this point the vertical plates meet one another, and the edge formed is rounded over to fit the interior of the bend of the horizontal angle iron so as to make the joint tight. Draw half size.

      The dimensions are as follows: angle irons 2½ inches × 2½ inches × ³⁄₈ inch; plates ³⁄₈ inch thick; rivets ¹¹⁄₁₆ inch diameter and 2 inches pitch.

      Exercise 10: Gusset Stay.—In order that the flat ends of a steam boiler may not be bulged out by the pressure of the steam they are strengthened by means of stays. One form of boiler stay, called a 'gusset stay,' is shown in fig. 8. This stay consists of a strip of wrought-iron plate which passes in a diagonal direction from the flat end of the boiler to the cylindrical shell. One end of this plate is placed between and riveted to two angle irons which are riveted to the shell of the boiler. A similar arrangement connects the other end of the stay plate to the flat end of the boiler. In this example the stay or gusset plate is ¾ of an inch thick; the angle irons are 4 inches broad and ½ inch thick. The rivets are 1 inch in diameter. The same figure also illustrates the most common method of connecting the ends of a boiler to the shell. The end plates are flanged or bent over at right angles and riveted to the shell as shown. The radius of the inside curve at the angle of the flange is 1¼ inches. Draw this example to a scale of 3 inches to 1 foot.

       Fig. 7.

       Fig. 8.

III. SCREWS, BOLTS, AND NUTS.

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      Screw Threads.—The various forms of screw threads used in machine construction are shown in fig. 9. The Whitworth V thread is shown at (a). This is the standard form of triangular thread used in this country. The angle between the sides of the V is 55°, and one-sixth of the total depth is rounded off both at the top and bottom. At (b) is shown the Sellers V thread, which is the standard triangular thread used by engineers in America. In this form of thread the angle between the sides of the V is 60°, and one-eighth of the total depth is cut square off at the top and bottom. The Square thread is shown at (c). This form is principally used for transmitting motion.