Neftegaz.RU #3-17 ENG

EQUIPMENT
FIG. 4. Diagram of the mine rock destruction with elementary section of the cutting element in
the process of drilling
Computational pattern for
mathematical description of the
cutting process with a cutter having
single width [1], given in the Figure
4, is proposed based on the analysis
of the records made in the process
of drilling and planning with various
thickness of the cut rock layer and
shares elements.
It was established that shear angle
of any element to the nearest
exposed surface slightly differs from
the rock shear angle , and the ratio
of the chipping contact height to the
shear line , is a constant
value and falls within the limits of
4 – 4.5 as applied to hard rocks.
It means that inclination angle
forming large and small waves on
the downhole undulated surface
in the process of drilling shall be
determined using the following
equation:
and falls within
the limits from 12.8° to 14.5°.
In order to prevent cutting elements
touchdown on the rear edge in the
process of propagation through
the top part at down grade of each
wave, the rear angle shall be more
than 14.5°. Let us take = 15°. As
RDT reinforced with PCD inserts
have constructively interrelated
front angle and the rear angle
(at the sharpening angle = 90°),
the maximum negativeness at
the minimum increase of the
cutting force for new boring bits is
represented by the front angle
equal 15°.
With consideration of the conducted
investigations, we have been the
first to propose the boring bits
reinforced with PCD for drilling of the
mine rocks of the VI – VIII drillability
class (RF Patent 2359103), RF
No. 242613, RF No. 2435927, RF
FIG. 5. The stabilizing anti-vibration boring bit, profile view
No. 2577351), and the stabilizing
anti-vibration boring bit has been
designed, manufactured and tested.
The stabilizing anti-vibration boring
bit (Fig. 5, 6) has a body 1 with с
connecting thread 2, divided by the
main water ports 3 into segments
4, which on the end surface are
provided with polycrystalline
diamond inserts 5, differently
directed at the angle of -15° to the
direction of cutting.
The main water ports 3 and auxiliary
water ports 6 are designed in
counter-current direction angle-wise.
The main 3 and auxiliary 6 water
ports are provided along the whole
body 1 height in screw line to the
right in the bit rotation direction.
Height of the bit body 1 depends
on the screw line pitch of the main
3 and auxiliary 6 water ports; inside
the auxiliary water ports 6 there
are two or more polycrystalline
diamond calibration inserts 7, each
of them represents the element of
a separate screw line, these inserts
are attached to the body by means
of soldering and are designed for the
well side wall processing.
When highly-abrasive rocks are
drilled, the bit is equipped with not
two but four rows of the calibrators,
i.e. 12 pieces of PCD 10 mm.
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