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PROFESSIONAL ADVICE
TECHNOLOGY OF OPERATION OF THE
FLAT GRINDING BRH 20A II LATHE
To help the technologist of the
production site
FOREWORD
The need to write this manual is due to the presence
of two factors. The first, objective, is predetermined by
the fact that of the whole series of grinding machines,
the most exploited at the machine-building enterprises of
Russia are surface grinding machines. At one time, at the
end of the 80s of the last century, in the framework of the
economic integration of the Comecon countries into the by the grinding operator.
Soviet Union, machines from the GDR, Czechoslovakia, However, the problem is
Romania, etc., including grinding, went in a wide flow. that the job responsibilities for
Now, at many machine-building enterprises of the Russian operating a surface grinding
Federation, those foreign machines continue to work, machine for the grinding
waiting for a change. A change they should come in the operator at many of our machine-
form of more modern machines, but already Russian- building enterprises are not
made. So, at least, that’s how it is planned. But when will even mentioned. What makes it
this shift come? Therefore, the veterans of the machine impossible to organize the system
tool park of Russia should not be weakened, in the sense of preventive maintenance BRH
of their skilled operation. In a number of foreign grinding 20A II in the time indicated by
machines in our country, the most widely represented is a its technical documentation. This
surface grinding machine type BRH 20A of Czechoslovak circumstance predetermines the
production. Unfortunately, this category of machines of second, already subjective, factor
the last century is now being operated on the residual - the technical incompetence of
principle, with the squeezing of the latest production the shop managers regarding the
resources from them. Moreover, the BRH 20A lathe are organization of routine maintenance,
operated in the conditions of the complete absence of in particular surface grinding
branded spare parts and consumables. machine, at the appropriate time,
Accordingly, in such critical conditions, these machines within the framework of the rules for
require a very careful attitude to observing the technology its operation.
of their operation and maintenance. Undoubtedly, the The proposed manual has the
organization of their proper operation is completely and following objectives: specification
completely the prerogative of shop-floor managers, of the specifics of operation of the
including production site technologists. These managers surface grinding machine BRH
are required to responsibly observe the operation 20A II at a conceptual level and
technology of the machine in question by monitoring the assistance to the management
implementation of the rules for its routine maintenance of the shop floor in organizing its
planned routine maintenance.
The manual will also be useful for
the operator of a surface grinding
machine of this type in terms
of consolidating his theoretical
knowledge and practical skills.
GENERAL INFORMATION
For work on the BRH 20A
lathe it is recommended to use
grinding wheels of the following
sizes:
● d1 = 250 × 20 × 76;
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PROFESSIONAL ADVICE
● d2 = 200 × 20 × 51.
The minimum wear diameter of the
grinding wheel is 120 mm, the maximum
total width of individual twin wheels is 100
mm. The optimum peripheral speed (V
okr.) of these grinding wheels is 35 m / s.
Oil change in the grinding (spindle)
headstock should be carried out once every
3 months. The amount of oil refilled in the
grinding headstock is 0.3 l. The viscosity
of the oil is 3.9 ... 6.2 / 20° C. Russian I
5A oil is a replacing for Czech OL-OT oil.
Coolant tank filling capacity - 63
l. Composition of coolant: water - 95%,
emulsol - 2.5%, soda ash - 2.5%. During operation, the coolant must not fall
Coolant replacement – once every
six months (with cleaning the tank of on a non-rotating circle.
The magnetic (electromagnetic) plate
dirt). When replacing the coolant, it is should be periodically grinded to exclude non-
mandatory to clean the magnetic dirt trap planar installation of the grinding part.
from mechanical impurities in the form of When cleaning the lathe from dust and dirt,
silty deposits and check its serviceability. the use of compressed air is prohibited. Clean with
When installing a new grinding
a vacuum cleaner and a lint free cloth.
wheel, observe the following rules: Do not place the tool on the guides of the
● check the circle for possible cracks table and bed of the grinding head of the lathe.
(shells) by tapping it with a wooden
hammer, when tapping, the sound should LATHE SETTING
be clean, without rattling;
● when fixing the circle on the spindle, ADJUSTING OF DUMPING OF EXTREME
pay attention to the condition of the TABLE POSITIONS (Fig. 1)
adapter flanges and nuts; uneven in size With a correctly selected table speed, the
or bent adapter flanges when tightening damping value is regulated by a throttle valve (2).
the nuts create uneven pressure on the
Turning the throttle valve control (1) clockwise
circle, which can lead to its destruction; softens the table damping process. When rotated
worn nuts must be replaced; counterclockwise, damping becomes harder.
● between the transitional flanges and the
circle it is necessary to install elastic gaskets: Note: the control element (1) by the throttle
cardboard or leather, the diameter of the
valve is located on the front panel of the machine
gaskets must be at least 2 mm larger than - under the handwheel for manual movement of
the diameter of the transitional flanges; the table.
gasket thickness - 2 mm; gaskets before
installation should be oiled to protect SETTING AND CONTROL OF THE PRESSURE
against soaking under the influence of
OF THE WORKING LIQUID IN THE HYDRAULIC
coolant; SYSTEM (Fig. 2)
● assembly of the circle and adapter
flanges is performed using a torque wrench; The pressure in the hydraulic operating circuit
first tighten the mounting screws to gently is regulated by the bypass valve (5). The pressure
tighten the circle, then alternately tighten in the hydraulic control circuit is controlled by a
the diametrically opposite screws of the bypass valve (7).
adapter flanges with a torque wrench;
● when installing a circle on a machine Note: adjustment of the indicated valves by
spindle, it is forbidden to hit it with metal the required value is carried out only by a qualified
objects; in order to remove the circle mechanic-adjuster, if necessary.
from the spindle, you must first unscrew The pressure in the hydraulic circuits of
the screws and remove the outer adapter the machine should correspond to the following
flange, which secures the circle; values: hydraulic working circuit – 1.2 MPa;
● before starting work, you should hydraulic control circuit – 2 MPa.
test a new circle at idle for 5 to 10 minutes.
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