Page 263 - Modular design for machine tools

222 Engineering Design for Machine Tool Joints

TABLE 6-5 Values of C and m for Joints under Higher Interface Pressure
= 1.0 mm
(i) Ground surface R max (ii) Lapped surface R max = 1.4 mm
D/h m C D/h m C
100/40 0.40 0.089 100/40 0.54 0.051
80/40 0.36 0.046 80/40 0.60 0.039
60/40 0.75 0.017 60/40 0.60 0.032
50/40 0.58 0.008 50/40 — —
100/24 0.39 0.090 100/24 0.56 0.045
80/24 0.58 0.053 80/24 0.43 0.074
60/24 0.61 0.022 60/24 0.55 0.027
50/24 0.21 0.048 50/24 — —
Average 0.48 0.046 Average 0.55 0.045
P = 2 tonf

fD h

40 mm
f100 mm

Joint material: semihard steel
(S45C of JIS)
Note: Values of C and m are available when l and p are in micrometers and
megapascals, respectively.

of Ostrovskii’s expression in the case of steel-to-steel joint, and Ito and
Tsutsumi [11] reported the interesting behavior as follows.

1. The Ostrovskii expression can be used for the joint, where the inter-
2
face pressure is up to 100 kgf/cm . Table 6-5 shows the values for
C and m.
2. The value of m is around 0.5 as reported by Back et al. for the joint
with lower interface pressure, although the values of C differs largely
from those reported by Back et al.
3. In the joint with local deformation such as the bolted joint of the
column to the table guideway of planomiller, as already reported by
Kaminskaya, the joint stiffness should be determined to be smaller
than that calculated from Eq. (6-2).

Within this context, Connolly and Thornley proposed another expres-
7
sion, as already shown in Table 6-1. They emphasized that within a
machine tool design context, a root cause of the difficulties lies in the

7
They proposed later a modified expression to clarify the effects of the surface
roughness together with considering the waviness and flatness deviation [16].