The table is so arranged that the diameter (divided by distance between centres) of one step of a belted pair will always be found in the extreme right-hand column; while its companion step will be found on the same horizontal line, and in that vertical column of the table corresponding to the length of belt employed. For example, if column 14 of the table corresponded to the length of belt employed, some of the possible pairs of diameters would be as follows:
| .71 | 18 | .58 | 13 | .42 | .21 | 64 | .04 | 74 | |
| .06 | .24 | .42 | .60 | .72 |
The upper row of this series of pairs being taken from column 14, and the lower row from the extreme right-hand column, the numbers in each pair being on the same horizontal line. If the distance between the centers of the pulleys were 60 ins. the effective diameters of the steps corresponding to the above pairs would be:
| 42.7 | 1 | 34.8 | 8 | 25.2 | 12.9 | 8 | 2.8 | 4 | ins. | |
| 3.6 | 14.4 | 25.2 | 36.0 | 43.2 | 0 |
being obtained by multiplying the first series of pairs by 60; the length of belt which would be equally tight on each of these pairs would be 3.3195 × 60 ins. = 199.17 ins.
To get the actual diameters of these steps when thickness of belt = 7⁄32 = 0.22 in., we have simply to subtract 0.22 in. from the effective diameters just given, thus:
| 42.49 | 34.66 | 24.98 | 12.76 | 2.62 | in. |
| 3.38 | 14.18 | 24.98 | 35.78 | 42.98 |
would be the series of pairs of actual diameters.
In solving problems relating to the diameters of cone pulleys by means of the accompanying table, we must have, besides the distance between centres, sufficient data to determine the column representing the length of belt. The length of belt is seldom known because it is of small practical importance to know its exact length; but it may be estimated approximately, and then the determination of suitable diameters of the steps becomes an extremely simple matter, as may be seen from what has already preceded. When the length of the belt is not known, and has not been assumed, we indirectly prescribe the length of belt by assuming the effective diameters of the two steps of a belted pair; thus, in the following [Figure (561)], the length of belt is prescribed when the distance a b, and any one of the pairs of steps d1d1, d2d2, d3d3 and d4d4 are given. We will show in the following examples how the length of belt and its corresponding column of diameter may be found when a pair of steps (like d1d1), are given.