How does a machine lathe work?
In this article
The machine lathe is a tool whose main function is to remove part of a workpiece by means of a cutting tool, so that it can be deformed for a specific purpose.
This process, known as turning, can be carried out on different materials, among which wood, plastic and metal are the most common. Its parts of revolution can be helices, cones and cylinders. In addition, it is sometimes used not for turning but for polishing, sanding or grooving parts.
How the machine lathe works
To perform its functions, the lathe must start from a part called the base, which is designed to remove parts of the workpieces in such a way that it is deformed in the process until the desired shape is obtained.
This action can be carried out through different movements, but the main one is rotation. Other possible movements are penetration or tool feed. The latter are characterised by their tendency to be rectilinear and, unlike the rotary movement, it is not the workpiece that comes to the machine but the cutting tool that reaches the workpiece.
Each of the three movements that a machine lathe can perform is of crucial importance in avoiding errors during the process of deforming the workpiece. In this regard, it should be mentioned that lathes are capable of creating parts of many different shapes, such as concave shapes, gears, convex shapes or threads, among others.
Parts of the machine lathe
To understand how a machine lathe works, it is necessary to know its parts. The fundamental ones are the following:
Bed
It forms the structure of the machine lathe. It is generally a fairly large cast body. In addition, it acts as a guide and support for the rest of the machine's parts.
Main shaft
It is here that the workpiece is placed so that it can perform the rotary movement. At one of its ends it has a shaft called the tailstock, which is movable and is intended to hold the workpiece at one point. It also has another end where the workpiece is held by means of a chuck. If desired, the chuck can be replaced by a spindle.
Tool carriage
As its name indicates, this is the carriage responsible for carrying the cutting tools and moving them as required. This carriage responsible for the movement comes in three different forms:
Main
Also called the longitudinal carriage, it can move from left to right along the bed. That is, it is the one that allows the feed movements of the workpiece. It can move both automatically and manually, and parallel to the axis of the machine lathe. The cross slide is located on top of this carriage.
Cross
The movement of this carriage is backwards or forwards perpendicular to the main carriage. Its main function is to allow depth to be given to the work. It can only be moved manually, by engaging the automatic cross-feed lever, or by turning the cross-feed handle. The auxiliary carriage is located on top of this carriage.
Auxiliary carriage
It consists of a base that swivels through 360° and its main function is to allow the penetration movement at certain angles or to make tapers. It can only be moved manually, by turning the screw handle.
It should be noted that the cutting tool is held in place by a tool turret located on this carriage. This turret allows several tools to be fitted during a single turning job, so that it can subsequently be rotated as necessary to work the part.
Norton gearbox
Lastly, the Norton gearbox is a part of the machine lathe responsible for allowing the feeds and thread pitches to be selected. It is controlled by levers that operate the set of gears inside the Norton gearbox.
How is the machine lathe used?
To use the machine lathe, you start by fixing the base workpiece to the mandrel of the lathe. The mandrel is the part located between the chuck and the main shaft. When the machine lathe is switched on, the mandrel can be made to rotate. It will also be possible to begin moving the carriages towards the cutting tool where the workpiece is located.
Through the auxiliary carriage it is possible to move the cutting tool to deform the workpiece as required. It is worth mentioning that it is often also necessary to manipulate the speed at which the workpiece rotates, as this influences aspects such as the durability of the cutting tool and the production volume.
For example, if the speed set is very low, production will be slow; if the speed is excessive, production will be higher, but the cutting tool will lose its edge more quickly, so the process will have to be stopped more often to re-sharpen the cutting tool.
Frequently asked questions
How does a lathe work?
A lathe removes part of a workpiece with a cutting tool while the workpiece rotates: rotation is the main movement, and the tool approaches the workpiece with straight feed and depth-of-cut movements. This process, turning, produces parts of revolution such as cylinders, cones or helixes in wood, plastic or metal, as well as concave and convex shapes or threads.
What are the main parts of a lathe?
The main ones are the bed, a cast iron structure that serves as guide and support; the main spindle, where the workpiece rotates, held in a chuck and supported by the tailstock; the tool carriages (longitudinal, cross and compound), with the turret that holds the tools; and the Norton gearbox, a set of gears operated by levers.
What are the lathe carriages for?
They carry the cutting tool and move it. The main or longitudinal carriage moves along the bed, parallel to the axis, manually or automatically; the cross slide, mounted on top, moves perpendicularly and sets the working depth; and the compound slide, on a 360° swivel base, allows angled infeed or taper turning, always by hand.
How does rotation speed affect the work of a lathe?
The speed at which the workpiece rotates affects the life of the cutting tool and the production volume. If it is too low, production is slow; if it is excessive, more is produced, but the tool loses its edge sooner and you have to stop more often to resharpen it. That is why it should be adjusted to each job.
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