SPANNTOP [nova] – Safety
Coefficients of
friction
For workpieces of a material other than steel, the va-
lues shown must be multiplied by the correction va-
lues specified below.
For hardened steel as the material, the values of the
smooth clamping heads always apply for ground
workpiece surfaces.
NOTE
Clamping of hardened materials or materials
with extremely high strength values
[R
m
> 1300 N/mm
2
] is only permitted with clam-
ping heads of the variants smooth, longitudinal
or transverse serration!
Other clamping head designs can be damaged
and lose their capacity of achieving higher co-
efficients of friction with soft materials.
Workpiece surface
Jaw clamping surface
Smooth
clamping head
Clamping head
with longitu-
dinal and trans-
verse serration
Clamping head
with Z-serration
Clamping head
with F-serration
Finely finished,
ground
μ
t
=
0,06
μ
a
=
0,08
μ
t
=
0,07
μ
a
=
0,09
μ
t
=
0,15
μ
a
=
0,20
μ
t
=
0,17
μ
a
=
0,22
Finished to
roughed
μ
t
=
0,10
μ
a
=
0,13
μ
t
=
0,11
μ
a
=
0,15
μ
t
=
0,18
μ
a
=
0,25
μ
t
=
0,23
μ
a
=
0,28
Rough machined
or unmachined
μ
t
=
0,14
μ
a
=
0,16
μ
t
=
0,16
μ
a
=
0,18
μ
t
=
0,20
μ
a
=
0,28
μ
t
=
0,25
μ
a
=
0,30
Material correction
values
Aluminum alloys
=
0,97
Ms 58
=
0,92
GG-18
=
0,80
Table 5: Friction coefficient for steel workpieces
28
