BS ISO 3408-5:2006

Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and subscripts
  4.1 Symbols
  4.2 Subscripts
5 Basic axial load ratings
  5.1 Basic static axial load rating, C[0a]
  5.2 Basic dynamic axial load rating, C[a]
6 Modified axial load ratings
  6.1 Modified static axial load rating, C[0am]
      6.1.1 General equation
      6.1.2 Correction for surface hardness, f[h0]
      6.1.3 Correction for accuracy, f[ac]
  6.2 Modified dynamic axial load rating, C[am]
      6.2.1 General equation
      6.2.2 Correction for surface hardness, f[h]
      6.2.3 Correction for accuracy, f[ac]
      6.2.4 Influence of material melting process, f[m]
7 Life
  7.1 Equivalent rotational speed and equivalent axial
      load
      7.1.1 General
      7.1.2 Ball screw with backlash between ball nut and
            screw shaft
      7.1.3 Ball screw with preloaded ball nuts on screw
            shaft
  7.2 Nominal life, L or L[h]
      7.2.1 Ball screw with backlash between ball nut and
            screw shaft
      7.2.2 Ball screw with preloaded ball nuts on screw
            shaft
      7.2.3 Resulting life, L[r]
      7.2.4 Nominal life, L[ar] or L[har], with reliability
            factor, f[ar]
  7.3 Modified life, L[m] or L[hm]
      7.3.1 Ball screw with backlash between ball nut and
            screw shaft
      7.3.2 Ball screw with preloaded ball nuts on screw
            shaft
      7.3.3 Modified resulting life, L[mr]
      7.3.4 Modified life, L[mar] or L[hmar], with reliability
            factor, f[ar]

Describes the calculation schemes for static and dynamic load ratings, and operational life, in order to obtain comparable values for the design and use of ball screws.

This part of ISO3408 specifies the calculation schemes for static and dynamic load ratings, and operational life, in order to obtain comparable values for the design and use of ball screws.

NOTE The calculations have been based primarily on publications by Prof. G. Lundberg and A. Palmgren Acta Politechnica, mech. Eng. series Vol. I, No. 3, Stockholm, Sweden. Part7, 1947.

This part of ISO3408 is applicable under the following preconditions:

• elastic deformation of ball and balltrack;

• hardness of balltrack basically exceeds a minimum of HRC 58;

• conformity f_rs and f_{r n}>0,5;

• the quality of steel of which the ball screw is made is equivalent to that of ball bearing steel or similar steel alloys;

• optimum lubrification is always provided.