NTN spherical roller bearings, 231 series: dimensions and part numbers

Every part number in this series carries a suffix after the basic designation. The most frequent NTN suffixes, with the number of sizes they appear in: B (18), BK (18), EMD1 (18), EMKD1 (18), and EAD1 (9). The suffix defines the variant (sealing, cage, internal clearance or other options): to request a quote, send us the full part number marked on the bearing, the box or the drawing.

How to read the part number: 231 gives the bearing type and the dimension series; for the same bore, each series has a different outside diameter and width. What follows is the bore code: from 04 upwards, multiplying by 5 gives the bore in millimetres (in the 23120, 20 × 5 = 100 mm); after a slash, the bore is given directly in millimetres (in the 231/500, 500 mm).

The table gives the boundary dimensions of each basic designation according to ISO 15, in millimetres: d is the bore, D the outside diameter and B the width. These are standardised dimensions: the same basic designation has the same dimensions in every brand. Where a dash appears, the dimension has not been validated yet: we confirm it when we quote.

If the part number on the bearing can no longer be read, measure the bore, the outside diameter and the width, and find the matching row: with that size and the variant you need, we will quote it.