The headstock - The back gear LATHE

The headstock The headstock is secured permanently on the inner ways as the left hand end of the lathe bed, and it provides mechanical means of rotating the work at multiple speeds. It comprises essentially a hollow spindle and mechanism for driving and alternating the spindle speed. All parts are housed within the head stock casting. The spindle of headstock is made of carbon or nickel-chrome steel. The back gear The back gear is an additional feature of a belt driven lathe and is used to obtain wider range of spindle speeds, for the number of speeds obtained from “direct speeds” is limited to number of steps only. When the back gear is engaged, the spindle is speed is reduced considerably. So it is also used when it is necessary to have a slow speed of the spindle that cannot other wise be obtained by direct speed. A slow speed is necessary in the following cases. 1.In turning jobs of large diameter within the available cutting speed of the material 2.In turning jobs tough or hard material when the material is hard it becomes necessary to apply greater cutting force by the tool to shear out the metal. This increase in cutting force will require greater turning torque necessitating slower spindle speed. 3.In operations like thread cutting, reaming, e.t.c. 4.In taking deep cut as rough turning.
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Unscrewing System

To remove a product that is threaded on the inside, the mold that form the screw must be rotated in the opposite direction from the direction of threaded products. Player power can be generated by a straight motion from the mold openings are converted into rotary motion by means of transmission such as worm gear, or by adding a separate player. Below are shown examples of mold unscrewing system with its own player. As the player is connected to a motor. With through existing trnsmisi gears on the axle TSB core rotates in the direction opposite the direction of threaded products. At the base of cores threaded bushing installed with the direction and magnitude equal pitch screw threaded products. Because the threaded bushing above also serves as a nut, then the opposite direction when the screw rotated cores, cores will retreat and escape from the grip of the product, wherewith products are free from cores driven down by stripper plate. At the opening of the next mold, plates 1 and 2 open, runner pin sinking of the surface of the plate so that the runner down. To avoid co-rotating products during core spinning off product, at the end of the tooth or indentation formed male.

Dimension lines

Various ISO standards are concerned with dimensioning. They are under the heading of the ISO 129 series. The basic standard is ISO 129:1985 but it has various parts to it. A dimensioning 'instruction' must consist of at least four things. Considering the 50mm width of the jaw and the 32mm spacing of the holes of the movable jaw drawing in Figure 3.15, these are" Two projection lines which extend from the part and show the beginning and end of the actual dimension. They are projected from the part drawing and show the dimension limits. In Figure 3.15, the width is 50mm and the projection lines for this dimension show the width of the part. They are type B lines (thin, continuous and straight). These lines touch the outline of the part. The projection lines for the hole-centre spacing dimension of 32mm are centre lines. They are type G lines (thin, discontinuous, chain) which pass through the drawing just past where the holes are located. A dimension line which is a type B line (thin, continuous and straight). In Figure 3.15, these dimension lines are the length of the dimension itself, i.e. '50' or '32' mm long. A numerical value which is a length or an angle. In the Figure 3.15 example the dimensions are the '50mm' and '32mm' values. If a part is not drawn full size because it is too small or too large with respect to the drawing sheet, the actual dimension will be the value which it is in real life whereas the dimension line is scaled to the length on the drawing. Two terminators to indicate the beginning and end of the dimension line. The terminators of '50' and '32' dimensions in Figure 3.15 are solid, narrow arrowheads. Other arrowhead types may be used. There are four types of arrowhead allowed in ISO, as shown in Figure 3.16. These four are the narrow/open (15~ the wide/open (90~ the narrow/closed (15 ~ and the narrow/solid (15~ An alternative to an arrowhead is the oblique stroke. When several dimensions are to be projected from the same position, the 'origin' indication is used, consisting of a small circle. These drawings are shown in Figure 3.16. An example of an origin indicator is shown in the movable jaw detailed drawing. Many dimensioning examples can be seen in the movable jaw and hardened insert detail drawings. The dimensions in these two drawings follow the following convention. All terminators are of the solid arrow type, all projection lines touch the outside of the part outline, all dimension numerical values are placed above the dimension lines and all dimension values can be read from the lefthand bottom corner of the drawings. 
Engineering Drawing for Manufacture
by Brian Griffiths
Publisher: Elsevier Science & Technology Books

The bed LATHE

Description and functions of lathe parts Following are the principal parts: 1 Bed. 2.Headstock. 3.Tailstock. 4.Carriage. 5.Feed mechanism. 6.Screw cutting mechanism. The bed The lathe bed forms the base of the machine. The headstock and the tailstock are located at either end of the bed and carriage rests over the lathe bed and slides on it. The bed should be seasoned naturally to avoid distortion or warp that may develop when it is cooled after the bed is cast. The guide ways of the lathe may be flat and inverted- v having included angle of 90. The bed material should have high compressive strength, should be wear resistance and absorb vibration cast iron alloyed with nickel and chromium forms a good material suitable for lathe.




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