The speeds of stones for file grinding and other similar rapid grinding is thus given in the “Grinders’ List.”
| Diameter of stone. | Revolutions per minute. | |
| ft. | in. | |
| 8 | 0 | 135 |
| 7 | 6 | 144 |
| 7 | 0 | 151 |
| 6 | 6 | 166 |
| 6 | 0 | 180 |
| 5 | 6 | 196 |
| 5 | 0 | 216 |
| 4 | 6 | 240 |
| 4 | 0 | 270 |
| 3 | 6 | 308 |
| 3 | 0 | 360 |
These speeds are obviously obtained by reducing the diameter of the pulley on the grindstone shaft each time the stone has worn down 6 inches less in diameter, and give a uniform velocity of stone if the 8 feet stone be driven with a pulley 32 inches in diameter. Each shift (or change of pulley) giving a pulley 2 inches less in diameter.
The following table (from the Mechanical World) is for the diameter of stones and the number of revolutions they should run per minute (not to be exceeded), with the diameter of change or shift pulleys required, varying each shift or change 21⁄2 inches, 21⁄4 inches, or 2 inches in diameter for each reduction of 6 inches in the diameter of the stone:—
| Diameter of stone. | Revolutions per minute. | Shift of pulleys in inches. | |||||
| 2 | 1⁄2 | 2 | 1⁄4 | 2 | |||
| ft. | in. | ||||||
| 8 | 0 | 135 | 40 | 36 | 32 | ||
| 7 | 6 | 144 | 37 | 1⁄2 | 33 | 3⁄4 | 30 |
| 7 | 0 | 154 | 35 | 31 | 1⁄2 | 28 | |
| 6 | 6 | 166 | 32 | 1⁄2 | 29 | 1⁄4 | 26 |
| 6 | 0 | 180 | 30 | 27 | 24 | ||
| 5 | 6 | 196 | 27 | 1⁄2 | 24 | 3⁄4 | 22 |
| 5 | 0 | 216 | 25 | 22 | 1⁄2 | 20 | |
| 4 | 6 | 240 | 22 | 1⁄2 | 20 | 1⁄4 | 18 |
| 4 | 0 | 270 | 20 | 18 | 16 | ||
| 3 | 6 | 308 | 17 | 1⁄2 | 15 | 3⁄4 | 14 |
| 3 | 0 | 360 | 15 | 13 | 1⁄2 | 12 | |
| 1 | 2 | 3 | 4 | 5 | |||
“Columns 3, 4, and 5 are given to show that if you start an 8 feet stone with, say, a countershaft pulley driving a 40 inch pulley on the grindstone spindle, and the stone makes the right number (135) of revolutions per minute, the reduction in the diameter of the pulley on the grinding-stone spindle, when the stone has been reduced 6 inches in diameter, will require to be also reduced 21⁄2 inches in diameter, or to shift from 40 inches to 371⁄2 inches, and so on similarly for columns 4 and 5. Any other suitable dimensions of pulley may be used for the stone when 8 feet in diameter, but the number of inches in each shift named, in order to be correct, will have to be proportional to the number of revolutions the stone should run, as given in column 2 of the table.”
Fig. 2059.