Tapered Roller Bearings · ISO 355 / DIN ISO 355 / GB/T 297
ISO 355 31300 Series Steep Angle Tapered Roller Bearings Specification
What ISO 355 fixes, what it deliberately leaves to another document, its equivalents, and the dimensional table.
ISO 355 fixes the boundary dimensions of metric tapered roller bearings — bore d, outside diameter D, the assembled width T and the separate cone width B and cup width C — and defines the alphanumeric designation system (for example 30205 in the older series notation) built on the diameter, width and contact-angle series.
Standard
ISO 355
Covers
Boundary dimensions of metric tapered roller bearings
Does not fix
It does not fix the load rating, which is ISO 281, nor the mounted setting: a tapered roller bearing is adjusted on assembly to an endplay or a preload, and no standard can decide that figure for your shaft and your temperature rise.
Equivalents
DIN ISO 355 is the identical adoption, DIN 720 the older national document for the same bearings, and GB/T 297 the Chinese equivalent. Inch tapered bearings are a separate lineage, covered by ANSI/ABMA 19.2.
Product
31300 Series Steep Angle Tapered Roller Bearings
Governing standards
ISO 355 / DIN ISO 355 / GB/T 297
Equivalence between the ISO, DIN and GB/T documents is dimensional: a bearing made to either mounts in the same seat. It is not an equivalence of load rating, tolerance class or internal clearance, each of which is fixed by a separate standard and declared separately.
ISO 355 covers boundary dimensions of metric tapered roller bearings. This page sets out what the standard fixes for 31300 series steep angle tapered roller bearings, what it deliberately leaves to other documents, its national equivalents, and the dimensional table supplied against it.
ISO 355 — Scope
ISO 355 fixes the boundary dimensions of metric tapered roller bearings — bore d, outside diameter D, the assembled width T and the separate cone width B and cup width C — and defines the alphanumeric designation system (for example 30205 in the older series notation) built on the diameter, width and contact-angle series.
What ISO 355 Does Not Fix
It does not fix the load rating, which is ISO 281, nor the mounted setting: a tapered roller bearing is adjusted on assembly to an endplay or a preload, and no standard can decide that figure for your shaft and your temperature rise.
This division of labour is the thing to carry away from any bearing standard. A boundary dimension standard makes bearings interchangeable; it does not make them equivalent. Two bearings of the same designation from different makers mount in the same seat and are not required to have the same load rating, the same internal design, the same cage or the same speed limit.
Dimensions Supplied to ISO 355
Designation
Bore d (mm)
Outer diameter D (mm)
Assembled width T (mm)
Width B (mm)
Width C (mm)
Contact angle a (deg)
Chamfer r min (mm)
31305
25
62
18.25
17
13
28.81
1.5
31306
30
72
20.75
19
14
28.81
1.5
31307
35
80
22.75
21
15
28.81
2
31308
40
90
25.25
23
17
28.81
2
31309
45
100
27.25
25
18
28.81
2
31310
50
110
29.25
27
19
28.81
2.5
31311
55
120
31.5
29
21
28.81
2.5
31312
60
130
33.5
31
22
28.81
3
31313
65
140
36
33
23
28.81
3
31314
70
150
38
35
25
28.81
3
31315
75
160
40
37
26
28.81
3
31316
80
170
42.5
39
27
28.81
3
31317
85
180
44.5
41
28
28.81
4
31318
90
190
46.5
43
30
28.81
4
31319
95
200
49.5
45
32
28.81
4
Catalog Products Governed by ISO 355
ISO 355 governs more than this one series. In this catalog it applies to:
ISO 355 is the international reference and the right one to cite on a new drawing or a purchase specification. Adding the national equivalents alongside it costs nothing and makes the requirement legible to a supplier working to DIN or to GB/T.
Other ways to specify the 31300 Series Steep Angle Tapered Roller Bearings
The same part is also governed by GB/T 297 and DIN 720, and where two standards cover one dimension they agree — the numbers are the same, the document is not.
Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the designation snaps the other fields to that size's standard values; you can then override any individual value.
Sends the selected values to the quote form below.
Our facility
Where these dimensions are actually made
Ring forging, heat treatment, raceway grinding and superfinishing all happen under one roof, so a bore tolerance and a clearance group are set by processes we control and can evidence, not by whichever supplier had stock.
Request a Quote
The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.
Dimensions & Specifications (ISO 355 / DIN ISO 355 / GB/T 297)
Designation
Bore d (mm)
Outer diameter D (mm)
Assembled width T (mm)
Width B (mm)
Width C (mm)
Contact angle a (deg)
Chamfer r min (mm)
31305
25
62
18.25
17
13
28.81
1.5
31306
30
72
20.75
19
14
28.81
1.5
31307
35
80
22.75
21
15
28.81
2
31308
40
90
25.25
23
17
28.81
2
31309
45
100
27.25
25
18
28.81
2
31310
50
110
29.25
27
19
28.81
2.5
31311
55
120
31.5
29
21
28.81
2.5
31312
60
130
33.5
31
22
28.81
3
31313
65
140
36
33
23
28.81
3
31314
70
150
38
35
25
28.81
3
31315
75
160
40
37
26
28.81
3
31316
80
170
42.5
39
27
28.81
3
31317
85
180
44.5
41
28
28.81
4
31318
90
190
46.5
43
30
28.81
4
31319
95
200
49.5
45
32
28.81
4
Video: ISO 355 31300 Series Steep Angle Tapered Roller Bearings Specification
Third-party video, selected automatically for this topic. It is not produced by Bushing Bearings and is not a specification source — use the tables on this page for dimensional data.
Frequently Asked Questions
Does ISO 355 mean two bearings are interchangeable?
Dimensionally, yes — that is what a boundary dimension standard is for, and a bearing of the same designation from any maker mounts in the same shaft and housing seat. Functionally, not necessarily: the load rating, the internal design, the cage, the clearance group and the speed limit are decided by the manufacturer and by other standards, and two bearings with the same number are not required to match on any of them.
Does ISO 355 fix the load rating?
No. ISO 355 does not set load ratings. Basic dynamic load ratings are calculated to the method of ISO 281 and are declared by the manufacturer; the static rating follows ISO 76.
Which edition of ISO 355 does this table follow?
The table reproduces the dimensions we supply 31300 series steep angle tapered roller bearings to. We do not publish an edition year against it, so where the edition is contractually significant, cite the edition you require on the enquiry and we will confirm it against the table before quoting.
Can I cite the GB/T number instead of the ISO one?
For the boundary dimensions, yes — the GB/T standards restate the ISO dimension plan and a part made to either mounts in the same seat. The safest drawing note gives both, because it stays legible if the supply moves between a Chinese, a European and an international manufacturer.
How do I request a quotation?
Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.
Need a bearing quote or a spec sheet?Message our engineers on WhatsApp — send a drawing or DIN number and get pricing back fast.Start WhatsApp Chat →
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