Conventionally, any cutter for a metal lathe is represented by two elements: a head and a holder.
A head is a performing part consisting of a series of planes and cutting edges with a certain angle. Depending on the desired type of sharpening, the cutter is given a certain angle.
The holder is responsible for fixing the cutter in the holder of the turning device. It has a square or rectangular shape. There are a number of standard section sizes for each shape.
Design Varieties
The following types of cutters for a metal lathe are:
- Direct. The holder and head are located on the same or parallel axes.
- Curved. The holder has a bent shape when viewed from the side.
- Bent away. The head is bent to the holder when viewed from above.
- Drawn. The width of the holder is greater than that of the head. The head is located on the same axis with the holder or is offset in relation to it.
If you rely on the well-known classification of devices in accordance with GOST, then they are divided into the following types:
- With a cutting edge based on alloy steel. The tool is monolithic. It can be made of tool steel. Currently, its use is extremely rare.
- Filled with carbides. The edge plate is soldered to the head. This is the most common species.
- Hard alloy plates fixed by mechanical means. The cutting insert is fixed to the head with screws and clamps. Replaceable cutters are based on metal and cermets. This is the rarest species.
Directional classification
- The left model is fed to the left when taken in the left hand. The main working edge is located above the thumb.
- The right model, respectively, is fed to the right. The main working edge is under the thumb. In practice, it is more common.
Installation Methods
The cutter for the lathe for metal can vary in the installation method relative to the surface for processing:
- Radial view. When processing, the cutter takes a right angle to the axis of the workpiece for processing. This method is widely applicable in industrial enterprises. The cutter has a unified design for mounting on machines. It also has a more convenient selection of the geometric position of the cutting part.
- Tangential. During processing, the cutter is located to the axis of the workpiece at an angle different from the straight line. It has a more complex mounting method and is used on turning devices that allow high-purity processing.
Processing Method Difference
Cutters can be divided according to the processing method:
- fair;
- draft
- semi-finished;
- for work performed with particular subtlety.
The roughness of the tip of the fixture affects the roughness of the workpiece. A smooth surface is achieved by using a cutter sharpened under a large radius.
Types of turning tools
The cutter for a lathe for metal has many types. The most common are:
- Through passage. It creates the contours of the part during rotation, and also provides turning, trimming when feeding in the transverse and longitudinal directions.
- Boring appearance creates a variety of grooves, recesses and holes. Can make through holes.
- The scoring model is used only for the transverse direction of feed for turning parts with a stepped shape and end faces.
- Cutting off. Its supply is carried out in the transverse direction with respect to the axis of rotation. It produces grooves and grooves around the part, used to separate the finished product.
- Threaded. It cuts threads of any kind on parts with any section shape. This view can be curved, straight or round.
- Shaped. He turns the part of complex construction, can take out various chamfers inside and out.
A set of cutters for a metal lathe can be purchased in specialized stores or ordered online.
Cutter Base
The materials from which the devices are made are divided into three categories:
- The first is for cutting tools used at low speed. These are tool or carbon metals with a hardening index of 60-64. When the temperature of the cutter for a turning tool rises above 200-240 degrees, the quality of its cutting noticeably decreases, so in practice they are rarely used. This group includes devices based on chromium tungsten, chromium silicon and alloy steel with a level of resistance to temperature up to 300 degrees.
- The second category of cutters will be used at a high level of rotation of the head of the lathe. The basis of such devices is steel with a high cutting category P12 P9 or P9K5F2. After hardening, the material hardens to an index of 62-65 and retains all its properties at a temperature of 650 degrees. Not to be wiped for a long time.
- The third category is made of cermet-based cutters. These are carbide devices that operate at a high machine speed and can withstand temperatures of up to 1000 degrees. Cast iron and some parts of non-ferrous alloys are sharpened with tungsten-cobalt-based devices (VK6 for fine and semi-finished performance, VK8 for primary processing). Steel is turned with a hard alloy of titanium-tungsten-cobalt T15K6. In this case, clean processing is performed.
Desktop Lathes
Cutters for a desktop lathe for metal have a small cross section of 8 x 8 and 10 x 10 mm. They are used to process small parts.
Cutter inserts
The cutter for a lathe for metal of category T5 K10 is used for primary and intermittent turning. On the basis of cubic boron nitride, interchangeable plates are made for the processing of metals that are distinguished by their special hardness, including cast iron. Non-ferrous metals are turned by means of polycrystalline diamond.
The plates can be interchangeable. They are inserted into the holder. Some models contain chipbreakers that cut chips perfectly for low feed rates and surface turning. This kind of plate is used for high-purity cutting of stainless steel and other types of steel.
Tool sharpening
All kinds of cutters, in addition to interchangeable plates, are subject to sharpening from time to time. Sharpening the cutters for a lathe for metal ensures the achievement of the required values of angles and shapes. In industrial conditions, it is carried out on specialized units.
This process at home can be done through chemicals and grinding wheels. Manual grinding in terms of quality is inferior to industrial. The main thing here is the correct selection of the grinding wheel.
To grind carbide cutters, a circle of green carborundum is taken. Carbon turning tools are ground in corundum circles.
Sharpening is recommended to be carried out by means of cooling (uniform supply of cold water to the place of contact of the circle with the cutting tool). You can also dry sharpen, but after this, the part should not be lowered into cold water, as it may crack.
Standard grinding process
First of all, the main back face is subject to processing, then the back auxiliary one and only then the front part. At the very end of the process, the top of the fixture (radius of curvature) is processed. The sharpened cutter should be constantly moved on the surface of the grinding wheel and lightly pressed to the gouge.
An obligatory component of the process is the fine-tuning of the cutter, or rather the cutting edges (sections near the edge, the width of which reaches 4 mm).
Hard alloy devices are ground with copper donkeys, which are lubricated with a special paste compound or with a mixture of kerosene and boron carbide.
The remaining types of incisors are sharpened with a low abrasion-type donkey moistened with machine oil or kerosene.
Making homemade cutters
You can make homemade cutters for a lathe for metal. The basis of such devices are unnecessary broken drills.
Drill-based alignments do not break. In particular, they are suitable for lathes of the old modification. They are subject to repeated regrinding. Their service life reaches 30 years.
Homemade cutters for a mini metal lathe are made from the Heller saw segment. It is cut into a cutting disc.
How to make the right choice of cutter?
When choosing a cutter, a number of recommendations must be taken into account.
Determine what kind of metal you have to work with, what processing operations you plan, and to what extent the cutter will experience the load.
Decide what is most important - the accuracy of compliance with the geometry of the product or the level of surface treatment. Depending on this, the cutter is selected in accordance with the classification features and geometric proportions.
Indicate for yourself how important it is to comply with the condition for wear resistance of the device and how long it should remain unchanged.