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