STANDARDS UPDATE: CORRIGENDUMS TO ISO 4156-1 & 3

BGA Member Standards Update

We would like to draw your attention to corrections to ISO 4156-1 & 3 published in 2021 which were addressed in corrigenda (corrections) in December 2025.

ISO 4156-3:2021 Straight cylindrical involute splines — Metric module, side fit. Part 3- Inspection

An error in Figure 6 for external splines has been corrected in the update and, more importantly, an error in a sign in formula (9) for internal splines has been corrected has been corrected as shown below

ISO 4156-1:2021 Straight cylindrical involute splines — Metric module, side fit. Part 1- Generalities

In Annex A.4, the missing calculation for F_α, the calculation of the total profile deviation has been added

And an error in the Formula for calculating the diameter of measuring ball or pin for external spline D_Re in sections A.4, A.5, and A.6 have been corrected to read as follows:

This results in a change in the example value:

These ISO documents are not in the BGA’s standards library so you need to download the corrected documents from the website. Be aware that even with a corrigendum, the standard issue date will remain 2021.

Just a reminder that if you have any issues with any BSI or ISO standards: interpretation questions, suspected mistakes, typos or technical problems, please feel free to contact the BGA who will pass it on to the relevant standards committee. That is how this problem was identified and then fixed.