Lathe (tool)

The hand-operated screw-cutting lathe is the basic form of the universal lathe. Almost all turning procedures, except for the form of NC - turning, can be applied with it. Extensions such as Gewindeschneidapperate or the possibility of turning between centers predestine for use in single or small series production of simple turned parts, but larger quantities are made in low-wage countries on this model.

• 2.1 workpiece holder
• 2.2 Automatic feed
• 2.3 Tapping attachment
• 2.4 Bezel (Set Stock )

• 3.1 Copying Lathe
• 3.2 Mechanical rotary machine, multi-spindle machine

Basic components

Headstock

On the left side of the lathe is the headstock with drive gear and work spindle, at the end of the fixture, usually a lathe chuck can be mounted. A chuck used to clamp the workpiece or tool. The lining is removable, so you can use as needed a three - or four-jaw chuck, a collet chuck, a faceplate or other fixture.

The hollow design of the work spindle reduces swing weight, increases the dimensional stability, and it can be necessary also raw materials through long push up to the size of the work spindle bore. Thus, it is not necessary before machining to saw off these. This can save material and above all time.

The work spindle is driven via a belt drive by an electric motor. The speed can be varied in older lathes by throwing a belt or by a manual transmission. In modern lathes engines are usually fitted with stepless speed adjustment.

The advancing movement is derived from the work spindle on the gearbox, that switches the direction of feed. About change gears or timing belt is a link to the feed gear with which the feedrate is connected to control and feed rod. Since the feed rate is given in millimeters per revolution during the rotation, the speed of the work spindle is irrelevant. On newer machines, a ball screw replaces the guidance and feed rod.

Tool slide

On the machine bed of the tool slide ( support) can be manually operated with a crank or by automatic feed by train or lead screw to the left and right. The tool slide consists of carriage, cross slide, top slide and lock box. The sleigh bed is the supporting unit. On it moves the cross-axis cross slide, which is also connected through a gearbox to the lead screw. The uppermost unit is the parallel to the bed and arranged rotatable top slide with quick release adapter for tool holder. At the top slide only manual feed is often possible in a few usually larger center lathes also feed is switched on. Since the top slide is rotatably mounted, pointed cones can be turned with him. By connecting one feed and simultaneous process of the upper slide experienced turners can also rotate curves.

In order to work efficiently, a quick-change holder today with a suitable tool holder used ( see figure right ) for quickly turning tool change. Chance are still tensioner in use, in which the turning tool with two or three screws will be fixed in a holder. The tensioning of the turning tools directly on the top slide is no longer allowed today.

Are on the slide several tools in a rotatable device, the " turret " mounted, refers to the machine as a turret lathe. The turret tool slide consists of carriage, cross slide and turret. In the turrets, a distinction depending on the position of the axis, "Star Revolver" with a vertical axis and " revolver " with the horizontal axis.

Tailstock

On the right side of the machine bed can usually find a tailstock. It can be shifted to the left or right, and is clamped at each location. It contains a spindle, which can be via a crank and also move in can be a center point or a drill chuck ( for attaching various tools, such as drills, taps, etc. ) Clamp. The center point may be fixed or contact following.

Extensions

Workpiece holder

In the lathe chuck, the movements of each jaw about a transverse threads are coupled to the components to be clamped centrally. Can with your bum round and depending on the number of jaws (three or four) uniformly three -, four -, six- or eight -edged workpieces are clamped. Threaded bolt to the chuck means connecting it to a plate ( mount plate ) and the work spindle. For irregular shaped workpieces, or for eccentric tension in the individual production using a so-called face plate. Very long workpieces are often rotated " between centers ", ie: on the headstock side are driven plate and driver point, on the tailstock side a fixed or live center. If the workpiece to be machined over the complete length, it is assumed instead of the driven plate, which spans the periphery, a so-called face drivers. Since in some cases the concentricity of a jaw chuck is not enough, there's fodder for collets that are more accurate.

Automatic feed

In order to remove material evenly, there is an automatic feed. The purpose of the feed shaft, a shaft having a groove or a hexagonal rod along the machine bed that rotates in an adjustable ratio to the main spindle. A gear mechanism in the lock casing of the tool carriage transfers the rotational movement of the feed shaft to be attached to the lathe bed or rack on the spindle of the cross slide. The slides can be coupled and thereby moved in the longitudinal direction, with better lathes also mounted on the tool carriage cross slide in the transverse direction automatically proportionally.

Thread cutter

For exact coupling between the rotational motion and the longitudinal feed milling machines have next to the feed shaft often also a lead screw, mostly for threading, the drive components are in any way connected positively to the spindle drive. That Gears and possibly timing belt connecting the movements of rotary drive and longitudinal feed, but not a v-belt. In most cases, the lead screw is aware only loaded with small forces to ensure the accuracy of this drive for a long time. The shorthand for this is: feed rod for the power lead screw for accuracy.

Depending on the features of the lathe can be made using this coupling internal and external threads in all designs and sizes, such as trapezoidal, metric and Whithworthgewinde turn, for complex machines with additional koppelbarem plan rotary drive also bevel or taper thread. For large internal and external threads and rare threads the right ratio of rotation and feed by interchangeable gears in the feed gearing or by means of a rocker Norton ( a manual ) is set. The feed motion takes place here but not on the feed rod, but on the much more precise lead screw, has a trapezoidal threaded spindle, with modern machines and ball screw. With the thread profile correspondingly shaped turning tool and a matching with the pitch feed screw to allow easy turning.

Small internal and external threads are drilled with a cutting device which disengages and spins in order not to damage the drill or the cutting iron from an adjustable torque. In many cases, the effort but not worth it. Instead, the machine operator, the work spindle slowly rotates automatically or manually and holds the tool firmly by hand.

Bezel (Set Stock )

When editing long workpieces it is easy to vibrations. These lead to a wavy patterned surface of the workpiece ( chatter ), to increased wear of the spindle bearings as well as noise pollution. Also then presses the turning tool due to the machining forces may the workpiece from the axis of rotation, whereby the geometry of the workpiece is defective. Therefore, it is advisable to use a centering in these cases in the tailstock and push from the right against the workpiece.

If due to the desired shape of the workpiece is not possible or not sufficient to use a center point, the use of a bezel is necessary. The bezel is set between the chuck and slide firmly on the bed. A simple bezel comprises three hardened steel rods that are screwed individually to the inside and the outside and to be pressed at intervals of 120 ° radially against the workpiece. With suitable lubrication, this arrangement acts as a sliding bearing. Better lunettes have three ball bearing rollers, which rotate when pressed against the workpiece.

There are various designs, for example, a fixed bezel, as described above, or a follow rest. The follow rest is attached to the carriage and allows, for example, continuous processing and threading of long shafts or spindles.

Modifications and extensions of the simple lathe

Copying Lathe

Until the 1970s, copying lathes were made, allow the addition to the normal operation even imaging a turning contour shape. Here, a clamped flat template is traced with the two-dimensional image of the desired workpiece contour of a hydraulic sensing device; the inward and outward movements of the tracing pin is transmitted by a hydraulic on the cross feed and outward, while the longitudinal feed with fixed value is moved over the feed rod. Cut for cut, strip by strip is then placed at the infeed depth inward, the workpiece is machined along contour parallel in several so-called equidistant until the final shape is achieved.

Mechanical rotary machine, multi-spindle machine

In multi- spindle machines in multiple functionality of a single lathe be used in a machine several simultaneously driven feeds that are six, eight or more stations peripherally connected and work in time: at a station, the workpieces are loaded and unloaded at the next station is a made rough machining on other stations partly finishes, thread cutting or drilling operations.

• Turning ( procedure)
• Machine tool