| Many industrial concerns have workshops of their own. | | | | Cutting Tools |
| For therepair of worn shafts, the lathe machine is | | | | Metal-cutting tools are classified as single point or |
| excellent. Keywayslots can be machined by using a | | | | multiplepoint. The lathe and shaping machine use single |
| milling machine, while ashaping machine can do | | | | point cutting toolwhile the milling and drilling machines |
| machining of large flat areas. Adrilling machine does | | | | use multiple-point-cuttingtools. |
| drilling of holes. | | | | Metal is cut either by moving the work piece like in the |
| A skilled Maintenance Engineer should know how to | | | | lathe orby moving the tool like in the shaping machine, |
| use all thesemachines in order to make his own repairs | | | | drilling ormilling machine. Clearance angles must be |
| in a safe manner. Veryoften he has to supervise | | | | provided to prevent thetool surface below the cutting |
| machinists. The information belowshould be useful for | | | | edge from rubbing against the workpiece. Rake angles |
| that purpose. | | | | are often provided on cutting tools to cause awedging |
| Lathe Machine | | | | action in the formation of chips and to reduce friction |
| The lathe machine uses a single-point-cutting tool for a | | | | andheat. |
| varietyof turning, facing, and drilling jobs. Excess metal | | | | Tool Materials |
| is removedby rotating the work piece over the fixed | | | | In order to remove chips from a work piece, a cutting |
| cutting tool to formstraight or tapered cylindrical | | | | tool must beharder than the work piece and must |
| shapes, grooves, shoulders andscrew threads. It can | | | | maintain a cutting edge at thetemperature produced |
| also be used for facing flat surfaces onthe ends of | | | | by the friction of the cutting action. |
| cylindrical parts. | | | | Carbon Steel |
| The work piece is clamped onto a horizontal rotating | | | | Carbon steel tools even though comparatively |
| shaft by a | | | | inexpensive tend tolose cutting ability at temperatures |
| 3-jaw or 4-jaw chuck. The latter chuck can be used | | | | around 400 degree F (205degree C). |
| to cutoff-centered cylinders. The rotating horizontal | | | | High-Speed Steel |
| spindle to whichthe chuck is attached is usually driven | | | | High-speed steel, containing 18 percent tungsten, 4 |
| at speeds that can bevaried. | | | | percent chromium, |
| The cutting tool is fixed onto a tool rest and | | | | 1 percent vanadium, and only 0.5 to 0.8 percent carbon, |
| manipulated byhand. It can also be power driven on | | | | permits theoperation of tools twice or three times the |
| straight paths parallel orperpendicular to the work axis. | | | | speeds allowable withcarbon steel |
| This is useful for screw cutting. | | | | Cast Alloys |
| Internal turning known as boring results in the | | | | Cast-alloy cutting-tool materials containing cobalt, |
| enlargement ofan already existing hole. The holes are | | | | chromium, andtungsten are effective in cutting cast iron |
| more accurate inroundness, concentricity, and | | | | and retaining theircutting ability even when red hot. |
| parallelism than drilled holes. Ahole is bored with a | | | | Cemented Tungsten Carbide |
| single-point-cutting tool that feeds alongthe inside of the | | | | The hardness of Tungsten Carbide approaches that |
| work piece. | | | | of a diamond. |
| Shaping Machine | | | | Tungsten carbide tools can be operated at cutting |
| The shaping machine is used to machine flat surfaces, | | | | speeds many timeshigher than those used with |
| grooves,shoulders, T-slots, and angular surfaces with | | | | high-speed steel. |
| single-point tools. | | | | Oxides |
| The cutting tool on the shaper oscillates, cutting on the | | | | Ceramic, or oxide, tool tips consist primarily of fine |
| forwardstroke, with the work piece feeding | | | | aluminum oxidegrains, which are bonded together. |
| automatically toward the toolduring each return stroke. | | | | These are very hard. |
| Drilling Machine | | | | Cutting fluids |
| The drilling machine is used to cut holes in metal with a | | | | An overheated tool can become blunt and soft very |
| twistdrill. By changing the cutting tool, they can be used | | | | fast. Thereforevery often, cooling fluids cools the |
| to doreaming, boring, counter boring, countersinking, and | | | | cutting points of the tool. Thisserves to lubricate and |
| threading. | | | | cool. |
| Milling Machine | | | | Water is an excellent cooling medium, but it corrodes |
| The milling machine uses a rotating cutting tool to cut | | | | ferrousmaterials. Sulfurized mineral oil is one of the |
| flatsurfaces, grooves, and shoulders, inclined surfaces, | | | | most popular coolantsas it can both cool as well as |
| dovetails,and T-slots. Cutters of many shapes are | | | | lubricate. The sulfur prevents chipsfrom the work from |
| changed to cut differentgrooves. | | | | melting on to the tip of the tool. |