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METALWORKING EQUIPMENT METALWORKING EQUIPMENT
AND TOOLS AND TOOLS
The contribution of the rotation of the mandrel relative to the spindle in its radial
displacements can be estimated by the expression: the massive cylindrical part of the
mandrel and the spindle, in
the region of the control
platform 1, which restrained
the volumetric deformation
of the spindle, the radial

A quantitative analysis carried out using this dependence showed the insignificance of this movements of the control platform
contribution for all considered joint sizes and load application options. 2 of the spindle sharply increase. In
A detailed description and analysis of the nature of deformations and physical processes in the turn, the increase in the movement
considered tool joints occurring as a result of the action of the set of external loads specified of the control platform 1, caused by
above is given on the example of the HSK-A63 joint. the increase in radial load, slows
down. The massive cylindrical
part of the mandrel carries
with it the spindle material
a b interacting with it. The cross
Fig. 4. Pressure distribution on the section of the spindle in the region of the flat
contacting surfaces of the mandrel and end assumes an oval shape, as well as the
spindle at various values of radial force:
a) - 0 kN (clamp); b) - 5 kN. cross section of the spindle, and in the region of
control sites 3 and 4 at loads exceeding 4 kN.
The deformation of the conical part of the mandrel contributes to the offset of the mandrel
relative to the spindle. Figure 5, b illustrates the radial movements of the control pads 3 and 4
of the mandrel. In the initial section, up to about 3 kN, the curves are parallel, i.e. the shank
is practically not deformed under the action of radial load. With increasing radial deformations
(ovality) of the spindle, the deformations of the shank caused by the clamping force of the
mandrel decrease, and the curves diverge. Subsequently, the partial opening of the conical joint
due to deformations of the shank and spindle leads to the inclination of the mandrel, which
corresponds to a change in the direction of movements of platforms 3 and 4 in Fig. 5, b.
As the flat unfolds, the load on the conical joint increases, which partially opens (see the
movement of the sites 4 in Fig. 5, b) when exceeded 5 kN radial force.
a b The nature of the curves in Fig. 5 allows us to conclude that for radial forces exceeding
Fкр, the relative radial displacement of the mandrel and spindle does not occur in the form of
‘‘stall‘‘, as stated in [1], but is the result of complex spatial deformations of the mandrel and
Fig. 3. Critical loads (1, 3 and 5 - Fкр (x), Fкр (y) and Fcr (θ); 2, 4 and
Plots of contact pressure 6 corresponding approximating curves for the joint HSK-A63 - fig. а) and spindle, which cannot be taken into account using analytical models. Based on the calculation
on mating surfaces for a shoulder HSK-A100 - fig. b) results, the following conclusions can be drawn:
L = 94.5 mm with a radial pads, preceding the contact of flat surfaces, occurs due to ● when using the HSK joint, it
load of F = 0 and 4500 N are deformation of the structure when pulling the mandrel cone retains its operational properties for all
shown in Fig. 4. The information into the spindle. During the final tightening, multidirectional considered variants of radial loads not
presented in the figure allows deformations are partially compensated by the friction of flat exceeding a certain critical value. Joint
you to see a qualitative picture surfaces; tangential stresses are observed at reference sites deformations in this load range are
of the pressure redistribution on 1 and 2. commensurate with calculation errors.
the contacting surfaces of the The application of radial load changes the distribution In carrying out practical calculations,
mandrel when the radial load of contact pressure at the joints. A drop in contact pressure the compliance of the joints can be
changes. and a decrease in the limiting value of the friction force (rest neglected;
From the figures it follows friction) are observed in the upper part of the flat ring joint, ● when the load increases above
that after the application of and the reverse process is observed in the lower part. As F a certain critical value, axial, radial
the clamping force at the end increases, slippage occurs in those sections of the junction and angular displacements of the
and the cone of the mandrel, where the value of rest friction is exceeded. mandrel appear due to the pulling a b
contact areas arise (see Fig. 4, With a further increase in radial force, the flat ring of the mandrel and spindle and their Fig. 5. Radial movement of control sites: a) - at the end and cone
a), forming respectively a flat joint opens. The friction force acting between the contacting volumetric deformations. With a spindle; b) - on the cone of the spindle and mandrel.
annular surface and two distinct surfaces of the spindle and the mandrel disappears in the further increase in load, the compound
annular belts [3]. Measurement areas that have come out of contact. An even greater loses its operational properties. Failure,
of radial displacements in a flat increase in the radial load leads to the opening of the conical which is necessarily preceded by the disclosure of a flat joint, is accompanied by a sharp increase
annular joint shows that they joint — the contact pressure in the region of the annular in the compliance of the mandrel-spindle joint in the axial and radial directions;
have positive and negative zones disappears, and at the same time the contact on the ● in none of the load application variants, there was no complete slippage between the
directions for the spindle greater part of the flat ring joint disappears (see Fig. 4, b). mandrel and the spindle on the entire surface of the flat ring joint. Slip on a part of the surface
and mandrel, respectively. As can be seen from the graphs presented in Figure of the annular joint does not significantly affect the operational properties of the joint;
The movement of the control ● the distance from the end face of the spindle to the point of application of the radial
5, a, after the disappearance of the friction force between load (L), along with the dimensions of the joint, is the most important parameter characterizing

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