Table 5 Safety Factor Sz (Reference Value) - Rohm Norm RN 1391 Informaciones Y Directivas Generales Para El Empleo De Instalaciones De Sujeción Accionadas Por Fuer

2 | Reference Speed and Clamping Force Calculation
Safety factor S
The magnitude of the safety factor S
which the influencing parameters, such as load, clamping coefficient etc., can
be determined and on the degree of safety required.
It should be ≥ 2 wherever possible.
Influencing parameters
a) Overhung clamping lz ≤ dsp
b) No radial support from tailstock
c) Tool applied radially
d) No axial seating of workpiece
against jaws
e) Ratio of clamping length to dis-
tance between cutting and
clamping points
Table 5: Safety factor S
* Lower safety factors can be applied if the workpiece is supported in the tail-
stock or axially seated against the jaws.
Superimpositions of alternating forces are neglected because their influence
is very small in comparison with the total clamping force required. The safety
factors so determined are applicable if the following requirements are met:
Chuck in perfect condition, no damage, adequately lubricated (operating in-
structions followed to the letter).
No allowance has been made for the following loads acting on the chuck:
a) Unbalanced forces and moments produced by unsymmetrical workpieces
b) Weight of workpiece
For a precise calculation of the clamping force required for a given job, use
VDI Recommendation 3106.
Available from: Beuth-Verlag GmbH, Kamekestraße 8, D-50672 Köln, Ger-
many.
46 / 138
z
3
(Reference value)
z
depends on the degree of accuracy with
z
Safety factor S
z
New chucks Older chucks
(serviced regularly)
≥ 2.0 ≥ 2.4
≥ 4.0* ≥ 4.8*
RN-1391