The tool is carried at the other end of this slide, there being shown in the figure a cutting-off tool in position. At the end of the holder is a hub and three adjusting screws whose ends steady the work, and which are locked in their adjusted position by the chuck nuts shown.
The Power Required to Drive Cutting Tools.—From experiments made by Dr. Hartig, he concluded that by multiplying the weight of the metal cuttings removed per hour by certain decimal figures (or constants) the horse-power required to cut off that quantity of metal might be obtained. These decimal constants are as follows:
| Lbs. of metal | cut off per hour, | cast iron | × | .0314 | = | horse‑power required to drive the lathe. |
| „ | „ | wrought iron | × | .0327 | = | „ |
| „ | „ | steel | × | .4470 | = | „ |
For Planing Tools.
| Lbs. of | steel | cut off per hour | × | .1120 | = | horse-power required | to drive planer. |
| „ | wrought iron | „ | × | .0520 | = | „ | „ |
| „ | gun metal | „ | × | .0127 | = | „ | „ |
Chapter XI.—DRILLING AND BORING IN THE LATHE.
For drilling in the lathe, the twist drill is employed not only on account of its capacity to drill true, straight, and smooth holes, but also because its flutes afford free egress to the cuttings and obviate the necessity of frequently withdrawing the drill to clear the hole of the cuttings.