METAL- WORKING MACHINERY. 368 built in a iiiultitudi' of foriiis ami of various sizes, from the small machine used by jewelers to the large gun and ingot lathes capable of turning a eylin<ler 10 feet in diameter. See Fig. 2 on Plate of ilETAL-WoEIilNG ilAcmxEKi'. METAL- WORKING MACHINERY. FlO. 2. THREE-SPINDLB BOBINO MACBIXE. Boring if.citlXK.s. Boring machines are tools for l>oring cylindrical holes by means of an axially rotating tool; they vary greatly in form according to the ])urpose for which they are used, being made with from one to a dozen or more spindles, and for drilling horizontal or inclined holes. Boring machines for boring holes of large diameter, such as engine cylinders. Fia. 3. PFXcB. ordnance, hollow shafting, usually have a cylindrical tool head in which two or more separate tools are clamped. They are designed to drill horizontal, vertical or inclined holes. Fig. 2 shows a three-spindle vertical boring ma- chine. Drills and boring machines are often used for reaming holes made by |iunehing or for giving an exact cylindrical interior surface to a Pi>ciii.G >l.vcui.ES OR PiMiiE.s. Punchcs are used like drills for perforating metal plates and shapes for riveted connections, the hole be- ing made by the thrust of a cylindrical puncli in- stead of by a rotating drill. Single and multiple punches are built capable of ])unching one or sever.al holes at once. For light work punches are usually driven by belts, but for heavy work individual steam-engines or hydraulic cylinders are the nibtive powers used. Where holes are to be punched at regular intervals automatic spac- ing tables are often used in connection with punches. Fig. 3 shows a single punch of familiar construction. Horizontally acting inmclies arc also constructed. Fig. i. 8BEAR8. Shearing Machines. Shears are used for cutting oir or shearing metal plates and shapes, and resemble punches in const ru<'t ion and opera- tion except that the punching tool and ilie are replaced by cutting edges which slide past each other like the blades of ordinary .shears or scis- sors. Fig. 4 shows a familiar construction of plate shears; machines of this type are built wide enough to shear plates 10 feet wide. For shearing angle iron and other shapes special forms of shears are often made. FlO. 5. mVETKR, RrvETiNO Machines on Riveters. Riveter* are employed for driving and heading hot rivet* in making riveted connections in lioiler work, hollow casting, as. for example, au engine cylin- structural work, etc. They arc built in a great der. variety of forms, but most usual is a U-shapcd
