Neftegaz.RU #3-17 ENG

EQUIPMENT
DETERMINING OF THE RATIONAL
VALUES FOR BORING BITS
REINFORCING ELEMENTS
WORKING ANGLES
THE ARTICLE GIVES RATIONALE FOR CHOOSING CUTTING ELEMENTS WORKING FRONT AND REAR ANGLES
WITH CONSIDERATION OF THE EFFECT OF KINEMATIC, TECHNICAL, MINING-ENGINEERING OPERATION
CONDITIONS OF THE ROCK-DESTRUCTION TOOL USED IN THE PROCESS OF DRILLING WELLS FOR VARIOUS
APPLICATIONS
UDC 622.234
KEYWORDS: the angle of shear, shear with compression, shear and tension, the front angle, rear angle, sharpening angle, the
trajectory of cut, cutting force, area of bluntness.
Aleksandr A. Tretyak,
Candidate of Technical Sciences,
Senior Professor, Associate
Professor at the Department
of Oil and Gas Equipment and
Technologies,
Platov South-Russian State
Polytechnic University
Yuriy F. Litkevich,
Candidate of Technical
Sciences, Associate Professor
at the Department of Oil and Gas
Equipment and Technologies,
Platov South-Russian State
Polytechnic University
Konstantin A. Borisov,
Assistant at the Department
of Oil and Gas Equipment and
Technologies,
Platov South-Russian State
Polytechnic University
Conventional and modern cuttingtype
rock-destruction tools (RDT)
applied in the process of producing
and exploratory wells drilling are
reinforced with tungsten-cobalt
alloys and polycrystalline diamond
inserts (PCD). Working front and
rear sharpening angles of hard-alloy
RDTs are not interrelated due to
the fact that reinforcing inserts may
have various shapes and generally
PCDs are made in form of round
cylinders. Such inserts sharpening
angle equals 90°, the front angle
and rear angle are interrelated.
Cutting force Fcut and rock shears
formation depend on the front angle
value.
The Figure 1 shows the diagrams
of shears formation obtained using
cutting elements with various front
angles.
The larger is the front angle
negativeness the bigger is rock
resistance to cutting. The specified
angle value depends on kinematic,
technical, mining-engineering
conditions of the cutting procedure.
Experimental studies show [1], that
rock resistance to crushing R cr and
shearing R s are proportional to
contact resistance P c .
R cr = 0.24P c ;
R s = 0.06P c – for cutters with
positive front angle ;
R s = 0.07P c – for cutters with zero
front angle ;
R s = 0.08P c – for cutters with
negative front angle .
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