ISSN 1068-798X, Russian Engineering Research, 2017, Vol. 37, No. 7, pp. 626–627. © Allerton Press, Inc., 2017.
Original Russian Text © E.V. Artamonov, M.O. Chernyshov, T.E. Pomigalova, 2017, published in STIN, 2017, No. 2, pp. 22–24.
Improving the Performance of Modular Drills
with Interchangeable Cutting Heads
E. V. Artamonov*, M. O. Chernyshov, and T. E. Pomigalova
Tyumen State Oil and Gas University, Tyumen, Russia
Abstract—The stress state of interchangeable hard-alloy cutting heads of modular drills is studied. The influ-
ence of the structural parameters of the heads on the cutting stress and strain is established. Cutting heads of
increased strength and modular drills with improved performance are described.
Keywords: strength, performance, interchangeable cutting heads, hard alloy, modular drills
Practical experience with modular cutting tools,
including drills, shows that their performance largely
depends on the tool material, the cutting conditions,
and also the methods of basing and attachment of the
cutter, as well as its geometry .
Analysis of failure statistics for interchangeable
cutting heads of modular drills shows that they
undergo brittle failure (Fig. 1). For example, failure by
shearing, crumbling, and fracture accounts for 80% of
the total for hard-alloy cutting heads, according to
data from OOO Tyumen’stal’most and OAO Gaztur-
Drilling is the main procedure used to produce
holes in metal workpieces. As a rule, the holes pro-
duced are not absolutely regular cylinders. They have
an oval cross section, and in the longitudinal direction
they taper .
The hole diameter is always greater than the drill
diameter. This difference is sometimes known as the
hole gap. For standard high-speed steel drills (diame-
= 10–20 mm), the gap is 0.15–0.25 mm .
The influence of radial vibration and the gap on the
strength of the cutting region in hard-alloy drills was
considered in . On the basis of those results and
production tests, we may conclude that modular drills
equipped with interchangeable hard-alloy cutting
heads operate at high cutting speeds, which ensure the
appearance of tool vibration and wobble.
Therefore, the auxiliary cutting edges (blades)
operate under variable load. That leads to shear and
brittle failure of the cutting head’s periphery. Simula-
tion of the radial drill vibration (Fig. 2) permits the
determination of the constant contact areas at the pri-
mary cutting edge and the variable contact areas at the
secondary cutting edge of the drill, with different devi-
ation of the drill from the hole axis (0–0.1 mm).
The results of such numerical modeling (Fig. 3)
show that radial wobble of the auxiliary cutting edges,
with (0–0.1)-mm deviation of the drill from the hole
axis, is accompanied by proportional increase in the
maximum hazardous tensile stress σ
, which reaches a
maximum at the point of intersection of the primary
and auxiliary cutting edges. That corresponds to the
typical failure of such cutting heads in production
conditions. Hence, the strength and performance of
interchangeable hard-alloy cutting heads must be
improved by optimizing the cutter parameters.
On the basis of the foregoing, we have developed
new interchangeable hard-alloy cutting heads of
improved strength (Fig. 4). In comparison with the
Fig. 1. Failure of interchangeable cutting heads in modular
Fig. 2. Simulation of the radial wobble of the drill’s cutting
edges when the interchangeable cutting head deviates from
the hole axis: ε = 120°; (1) blade.