Intermediate gear has no effect on the change gear

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Intermediate gear has no effect on the change gear ratio. It simply acts as a connection between the two, and serves to keep the rotation of driver and driven in the same direction. In a compound gear train, the stud carries two wheels which are keyed together so that they rotate as a unit. Compound gear train is employed when the gear ratio is not possible to obtain with a simple gear train out of the given set of change gears. In modern lathes, quick change gears are available to obtain the correct gear ratio to cut a particular thread quickly by simply shifting the lever into different positions which are marked on the instruction plates of the machine.
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Lecture - 6
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Today’s Quote "It is not how much we do, but how much love we put in the doing. It is not how much we give, but how much love we put in the giving." ~ Mother Teresa
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Setting of Tools for Threading Fig. Setting threading tool for internal threading Fig. Setting threading tool for external threading Cutting tool should be set exactly at the height of centers and normal to the work piece axis. If it is incorrectly set, the thread angle will not be correct and the flanks formed will not be proper. This setting is essential both for external and internal threads. A center gauge is always used for setting the threading tool correctly as shown in figures.
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Feeding the Tool in Threading Fig. a) Straight feed Fig. b) Inclined feed Fig. c) Inclined feed using a form tool Large amount of material is removed in the form of chips and that leads to the jamming of the tool and the flanks of the threads will be rough. Limit only to the finishing on coarse threads. However, it can safely be used for threads having below 2 mm pitch. In this method (Fig. b) tool is fed at an angle (usually half of the thread angle) to the axis of the work. The tool is set, as usual, square with the work axis and the required inclination is obtained by swiveling the compound rest. Most of the cutting is done by the left edge and tip of the tool. When threading is to be done on a large scale, the tool form shown at Fig. (c) is preferred.
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  • Winter '15
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  • Lathe, TPI, Screw thread, Unified Thread Standard, L.H. Threads, R.H. Threads

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