Conventionally, any cutter for a metal lathe is represented by two elements: a head and a holder.
The head is an executing part, consisting of a number of planes and cutting edges with a certain angle. Depending on the required type of sharpening, the cutter is given a certain angle.
The holder is responsible for fixing the cutter in the lathe holder. It has a square or rectangular shape. There are a number of standard section sizes for each shape.
Design variations
There are the following types of cutters for a metal lathe:
- Straight. 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. The head is curved towards the holder when viewed from above.
- Drawn. The toolholder is wider than the head. The head is located onthe same axis with the toolholder or offset relative to it.
If we rely on the well-known classification of devices in accordance with GOST, then they are divided into the following types:
- Having a cutting edge based on alloy steel. The tool is monolithic. It can be made from tool steel. At present, its use is extremely rare.
- Stuffed with hard alloy soldering. The edge-plate is soldered to the head. This is the most common type.
- Carbide inserts fixed mechanically. The cutting plate is fixed on the head with screws and clamps. Replaceable cutters are based on metal and cermet. This is the rarest species.
Classification according to the direction of the serving movement
- The left model is served from the left when taken in the left hand. The main working edge is located above the thumb.
- The right model, respectively, is served from the right. The main working edge is under the thumb. In practice, it occurs more often.
How to install fixture
Cutter for metal lathe may differ in the way of installation relative to the surface to be processed:
- Radial view. When processing, the cutter takes a right angle to the axis of the workpiece for processing. This method is widely used in industrial enterprises. The cutter has a unified mounting design on the machines. He also possessesmore convenient choice of geometric positions of the cutting part.
- Tangential. When processing, the cutter is located to the axis of the workpiece at an angle other than a straight one. It has a more complex mounting method and is used on turning fixtures that allow high-purity machining.
Difference in processing method
Incisors can also be subdivided according to the processing method:
- finishing;
- draft;
- semi-finishing;
- for fine work.
The roughness of the workpiece is affected by the radius of roundness of the top of the fixture. A smooth surface is achieved by using a cutter sharpened under a large radius.
Types of turning tools
Cutter for metal lathe has many types. The most common are:
- Checkpoint. It creates contours of the part during rotation, and also provides turning, undercutting when feeding in the transverse and longitudinal direction.
- The boring look creates a variety of grooves, recesses and holes. Can make through holes.
- The scoring model will only be used for the transverse feed direction for turning parts that have a stepped shape and face.
- Cut-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. Cuts threads of any kind on parts with any section shape. This view can be curved,straight or round.
- Shaped. It turns complex parts, can take out various chamfers from the inside and outside.
A set of cutters for a metal lathe can be purchased at specialized stores or ordered online.
Incisor base
Materials from which devices are made are divided into three categories:
- The first is for cutting attachments used at low speed. These are tool or carbon metals with a hardness index of hardening 60-64. With an increase in the temperature of the cutter for a turning tool above 200-240 degrees, the quality of its cutting decreases markedly, so they are rarely used in practice. This group includes devices based on chromium tungsten, chromium silicon and alloy steel with a level of resistance to temperatures up to 300 degrees.
- The second category of cutters will be applied at a high level of rotation of the lathe head. The basis of such devices is steel with a high cutting category R12 R9 or R9K5F2. After hardening, the material hardens to 62-65 and retains all its properties at a temperature of 650 degrees. Cannot be wiped for a long time.
- The third category is cermet-based cutters. These are hard-alloy fixtures that operate at high machine speed and withstand heating temperatures up to 1000 degrees. Cast iron and some parts made of non-ferrous alloys are sharpened with devices onbased on tungsten-cob alt (VK6 for finishing and semi-finishing, VK8 for primary processing). The steel is turned with T15K6 titanium-tungsten-cob alt hard alloy. This does clean processing.
Desk Lathe Attachments
Cutters for a desktop metal lathe have a small section of 8 x 8 and 10 x 10 mm. They are used for processing small parts.
Incisors in the shape of indexable inserts
Cutter for metal lathe category T5 K10 is used for primary and intermittent turning. On the basis of cubic boron nitride, replaceable inserts are made for processing metals that are particularly hard, including cast iron. Non-ferrous metals are turned with polycrystalline diamond.
The plates can be interchangeable. They are inserted into the holder. Some models contain chip breakers that provide excellent chip breaking at low feed rates and surface turning. This type of insert is used for high-finish cutting of stainless steel and other types of steel.
Sharpening incisors
Any types of cutters, in addition to interchangeable inserts, are subject to sharpening from time to time. Sharpening cutters for a metal lathe ensures that the required angles and shapes are achieved. In industrial conditions, it is carried out on specialized units.
This process at home can be done throughchemicals and grinding wheels. Manual sharpening is inferior to industrial sharpening in terms of quality. The main thing here is the correct selection of the grinding wheel.
To sharpen carbide cutters, a circle of green carborundum is taken. Turning cutters made of carbon materials are sharpened with corundum wheels.
Sharpening is recommended to be carried out by means of cooling (uniform supply of cold water to the contact point of the wheel with the cutter being processed). You can also dry sharpen, but after that, the part should not be lowered into cold water, as it may crack.
Standard sharpening process diagram
First of all, the main back face is subject to processing, then the back auxiliary face, and only then the front part. At the very end of the process, the top of the fixture (radius of curvature) is processed. The cutter to be sharpened should be constantly moved on the surface of the grinding wheel and pressed lightly against the tool.
An obligatory component of the process is the finishing of the cutter, or rather the cutting edges (areas near the edge, the width of which reaches 4 mm).
Hard alloy devices are sharpened with copper whetstones, which are lubricated with a special compound in the form of a paste or a mixture of kerosene and boron carbide.
Other types of cutters are sharpened with a low abrasive whetstone moistened with machine oil or kerosene.
Making homemade cutters
You can also make homemade cutters for a metal lathe. Unnecessary broken drills are taken as the basis for such devices.
Drill-based centerings don't break. In particular, they are suitable for older lathes. They are subject to repeated regrinding. Their service life reaches 30 years.
Homemade cutters for a mini metal lathe are made from a Geller saw segment. It is cut with a cutting disc.
How to choose the right cutter?
When choosing a cutter, there are a number of recommendations to take into account.
Determine what kind of metal you have to work with, what machining operations you plan and how much stress the cutter will experience.
Decide what is most important - the accuracy of compliance with the geometry of the product or the level of processing of its surface. Depending on this, a cutter is selected in accordance with classifying features and geometric proportions.
Designate for yourself how important it is to comply with the condition of wear resistance of the device and how long it should remain unchanged.
