ISO 3408-2-2021 Ball screws — Part 2: Nominal diameters, leads, nut dimensions and mounting bolts — Metric series.
1 Scope
This document specifies the nominal diameters and nominal leads, mounting dimensions for ball screw nuts and mounting bolts for metric ball screws. It also gives preferred combinations of nominal diameter and nominal lead and a general plan which includes the additional combinations to he used when it becomes necessary to deviate from the preferred combinations.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3408-1, Ball screws — Part 1: Vocabulary and designation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3 408-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at
— I EC Electropedia: available at bltp://www.elect
6 Mounting dimensions for ball screw nuts, type B6, B8 and B4, A6 and C6
There are three series of standardized ball screw nut dimensions. In Tables 2, 3 and 4, different types of ball screw nuts are shown. The following list shows these series of ball screws along with the corresponding figures and dimension tables.
— Series 1 (internal recirculation): depicted in Figure 1 to 3; dimensions are shown in Table 2;
— Series 2 (internal recirculation): depicted in Figure 3 to 5; dimensions are shown in Table 3;
— Series 3 (external recirculation): depicted in Figure 3 to 5; dimensions are shown in Table 4.
Further design detail alternatives are given in Figure 6.
NOTE The character B in the type description, e.g. B4, represents the flange type and is based on the previous definition, where A represents round type, B two flats and C one flat flange type. The corresponding numbers represent the number of mounting holes on the flange (e.g. two flats flange type with 4 holes would be B4).ISO 3408-2 pdf download.