Fig. 1. To describe an Envelop for a Cone.

Let ABI be the given cone. From I as centre, with the radius IA, describe the arc CD; make CD; equal in length to the circumference of AB (which can be found by a reference to the table of the Circumferences of Circles;) draw the lines CI and DI; then the figure CDI will be that of the required surface of the cone.

Edges for folding or lapping to be allowed, drawing the lines paralled to CI and DI, as shown by the dotted lines.

Fig. 2. To describe a Frustrum of a Cone.

Let AB equal diameter of large end; FH diameter of small end; GK altitude. Produce AF and BH until they meet at E; with E as centre, and the radii EF and EA, describe the arcs CD and IJ; set off CD equal to that portion of the circumference of AB required for a pattern; draw the lines CI and DJ, cutting the centre at E.

Edges for folding or lapping to be allowed, drawing the lines parallel to CI and DJ, as shown by the dotted lines.

Obs. The term altitude denotes perpendicular height; as from G to K in Fig. 2.

Can Top Or Deck Flange

Fig. 3. To describe a Can Top or Deck Flange.

Let AB equal diameter of can, or base of a flange; CD diameter of opening in the top; EG altitude. Produce AC and BD until they meet at E; with E as centre, and the radii ED and EB, describe the curves IJ and HK; set off IJ equal to the circumference of the base AB; draw the lines IH and JK, cutting the centre at E.

Edges to be allowed.

Frustrum Of A Cone

Fig. 4. To describe a Pattern for, or an Envelop for a Frustrum of a Cone.

Describe the right angle ABE; make BD the altitude; draw the line CD at right angle to BE; make AB equal one-half the diameter of the large end, CD one-half the diameter of the small end; draw a line cutting the points A and C, and the line BE with E as a centre and the radius EC and EA describe the arcs FG and HI; set off FG equal to that portion of the circumference of the smallest end required for a pattern, draw the lines HF and IG, cutting the centre at E.

Edges for folding or laping to be allowed drawing the lines parallel to HF and IG.

When the work is to be riveted, punch the holes for the rivets on the lines HF and IG.

When the work is to be wired, or a flange laid off, it must be allowed as shown by the dotted lines over the arc HI.