Fig. 7. Use of Steel Square to Find Miter and Side of Octagon.
In [Fig. 7] the same process is shown applied to the octagon. The degree line in all the polygons is found by dividing 360 by the number of sides in the figure:
360 ÷ 8 = 45; and 45 ÷ 2 = 22½ degrees.
This gives the degree line for the octagon. Complete the process as was described for the other polygons.
By using the following figures for the various polygons, the miter lines may be found; but in these figures no account is taken of the relative size of sides to the foot as in the figures preceding:
| Triangle | 7 | in. and 4 in. |
| Pentagon | 11 | " " 8 " |
| Hexagon | 4 | " " 7 " |
| Heptagon | 12½ | " " 6 " |
| Octagon | 17 | " " 7 " |
| Nonagon | 22½ | " " 9 " |
| Decagon | 9½ | " " 3 " |
The miter is to be drawn along the line of the first column, as shown for the triangle in [Fig. 8], and for the hexagon in [Fig. 9].
In [Fig. 10] is shown a diagram for finding degrees on the square. For example, if a pitch of 35 degrees is required, use 813⁄32 on tongue and 12 on blade; if 45 degrees, use 12 on tongue and 12 on blade; etc.
