Geometry of a cutting tool
Cutting face:
This is the face on which the chip slides. It is called Ag (g: gamma reading)
Flank:
It rubs the surface on which the material remaining on the play after tearing the chip.
It is called Aa (a: read alpha)
Cutting angles:
Information on cutting tools
Alpha (I) angle. This is the angle which prevents the tool heels (key) faces machined. It is measured between Ps and Aa in the projection plane Po, Po (orthogonal) is the plane in which one measures the angle or Pn (plane normal).
Beta (SSI): cutting angle. Is the angle defined by the limits of matter, therefore, between Aa and Ag projection Pi
Gamma (gi): cutting angle. This is the angle that gives the sharpness of the tool. It is measured between Pr and Ag in the plane of projection Pi As the angle is low over the cutting tool, but it is fragile, so a compromise is necessary at this level. It is the largest angle of the cut.
Note: for a cut positive, the sum of these three angles is 90 °. To cut a negative sum of the absolute value of these three angles is greater than 90 °.
Kappa (k r) steering angle edge. It is measured between Ps and Pf in Pr
Phi (yr): complementary angle to the direction of edge. It is measured between Ps and Pp in Pr
Note: The sum of these two angles is equal in all cases 90 °.
Kappa prime (k r ‘): steering angle side edge. It is measured between Ps’ in Pr and Pf
Lambda (l s): angle edge. It is measured from the cutting edge in Ps and Pr s
Epsilon (e r): angle of beak (nose of the tool). It is measured between the main cutting edge and s the cutting edge
Secondary s’ in Pr
Note: These angles are normalized and projected in planes. The index of the angle corresponds to the plane in
which it is intended. These angles are available for all tools.
Material of cutting tool:
The high-speed steel (for high speed steel) High-speed steels appeared about 1890 and are due to work
Taylor and White Americans. These are alloy steels. The metals are additive, tungsten (W), the
molybdenum (D), vanadium (V), cobalt (K) and chromium (C). The percentage of carbon in turn varies from 0.8 to 1.75%.
Carbides: they appeared in 1926 and have continued to be improved. They are now part of the tool
commonly used in mechanics for metal cutting. It is a mixture of powdered iron carbide sintered
often coated with alloy hardness, to facilitate sliding of the chip on the tool and heat dissipation.
The thickness of these layers varies from 4 to 10 microns.
Ceramics: the first cutting ceramic aluminum oxide appeared around 1920 in Germany
but without knowing a great success. Especially during the Second World War that the work on ceramics have led to concrete achievements. Unfortunately these tools were very fragile and above were not available at the time of machines and fast powerful enough for full use. Control of the microstructure of ceramics has led to considerable progress. The name comes from the ceramic structure of these materials which resembles hexagonal structure type porcelain.
Ceramics allow cutting speeds four times higher than the carbides and retain their hardness at higher temperatures (up to 1000 ° C).
There are two types of ceramics:
Information on cutting tools2
- Ceramic White (also called pure ceramic) is of aluminum oxide plus a few additives. Platelets are obtained by cold pressing (also called tabletting) followed by sintering.
- The black ceramic (also called mixed ceramic or cermet) is a mixture of aluminum oxide (¸ 70%) and titanium carbide (¸ 30%). It is obtained by pressure sintering.
These two types of ceramic pads come in different forms (such as fuel).
Diamond: In 1966, Dr. Tracy Hall, a research firm in Mégadiamond Corporation in the U.S. for the first time fabricated a sintered polycrystalline diamond. Diamond is the hardest material, but also the most expensive, but it is still much cheaper than single crystal diamond. It has a wear resistance than other tool materials do not, especially for highly abrasive materials. However, the polycrystalline diamond can withstand temperatures above 850 ° C, so it cannot be used for machining steel or cast iron. The development of polycrystalline diamond is: powder, prepared beforehand, is placed in a matrix of the desired shape.
This matrix is then placed in a press with a pressure of about one million bars. Simultaneously, electrically heated diamond powder to the sintering temperature of about 2100 ° C. This tablet is then cooled still under pressure.