Publisher's Synopsis
Excerpt from Henley's Encyclopaedia of Practical Engineering and Allied Trades, Vol. 3
The early drilling machines were built to drill one or more holes, using vertical spindles on flat plates singly, which plates had to be bent subsequently. The result was that after the plates were bent, the holes would not match, and drifting was resorted to, just as when the punch was used. Then followed the mount ing of the rings on rollers, the shell lying with its axis in a horizontal direction, and bringing radial drilling machines over the seams. These commanded both longitudinal and circular seams, but the spacing had to be done by hand to centre p0ps, or circles of rivet holes previously marked from templet, or by hand. A good many of these machines were made, and are still in use. Soon the multiple spindle design was introduced, but in a rather crude fashion. The shells were suspended verti cally, and the seams drilled by means of two or more drills Operating round the circumferential seams, and driven simultaneously. But the drills had to be set and started, and withdrawn by hand, and so the economy sometimes was often less than that of a single spindle machine. Several circular settings were necessary before the shell could be completed, and for every hole in the longitudinal seams the shell had to be lifted and reset. Following this came the em ployment of two drilling heads on opposite sides of the shell, with spindles also on the inside for countersinking, or removing the arris. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
