30200 Series Tapered Roller Bearings

The light tapered series, and the one most machines are actually built around: a 30204 is 20 mm bore, 47 mm outside diameter and 15.25 mm wide overall. The three digits are the usual three segments — 3 is the type, 02 the dimension series, 04 the bore code — so the standard's 02-series table starts at bore code 04 (20 mm); the smaller 30202 and 30203 are catalogue items and are tabulated here as well. A tapered roller carries radial and axial load together, which is why its width appears three times: B is the inner ring, C the outer ring, T the two assembled.

A tapered roller bearing is the first type here that cannot be described by one width, and the reason is mechanical rather than editorial. Its two rings are separate components that interpenetrate along the axis: the inner ring carries the rollers and the cage, and the outer ring is the seat. ISO 355 therefore gives three numbers where ISO 15 gives one. T is the total width of the assembled bearing — what the mounting has to accommodate. B is the inner ring width, and C the outer ring width. On a 30204 they are 15.25, 14 and 12 mm, and B + C comes to 26 mm — more than T, which looks like a contradiction until you see that the two rings overlap. That overlap is the whole point: it is the axial space in which the bearing is adjusted.

The designation reads the usual way. 30204 is type 3, dimension series 02 and bore code 04 — 20 mm. The bore-code rule is exactly the one the rest of this library uses: 00, 01, 02 and 03 are 10, 12, 15 and 17 mm, and from 04 upwards the code is multiplied by five. One wrinkle is worth knowing: ISO 355's own 02-series table begins at bore code 04, so the standard tabulates the series from 20 mm upwards. The 30202 and 30203 — 15 mm and 17 mm bores — are catalogue items rather than standard ones. Six independent sources agree on their dimensions, so they are tabulated here too; what the standard's silence means is that a designer who needs one should confirm supply rather than assume it.

The series runs from 30202 (15 mm bore, 35 mm outside diameter and 11.75 mm total width) to 30220 (100 mm bore, 180 mm outside diameter, 37 mm total width). Comparing it with the ball ladder at a single bore is the fastest way to see what the type buys and what it costs. On a 25 mm shaft a 6205 is 52 mm across and 15 mm wide; a 30205 is 52 mm across — the same housing bore — and 16.25 mm wide. The penalties are elsewhere: a tapered roller is heavier, needs axial adjustment at mounting, and generally runs at lower speed for the same accuracy. What it buys is the ability to carry a heavy axial load and a radial load at once in a single bearing.

Every designation in the table below links to its own page with the ISO 355 boundary dimensions including the T / B / C breakdown, the bore-code arithmetic, the same-bore comparison against every other series of all three types, and an explanation of why this type has no radial internal clearance group to print.

This series runs from a 15 mm to a 100 mm bore. The sub-library as a whole reaches 200 mm, and the widest single bearing in it is a 6340, 420 mm across, in the 6300 series. This one stops short of it.

d = bore diameter, D = outside diameter, T = total width, B = inner ring width, C = outer ring width. All of them are ISO 355 standard values and are the same for every manufacturer. T is the assembled bearing, B the inner ring and C the outer ring — and B + C exceeds T, because the two rings interpenetrate along the axis. That is why a tapered roller needs three widths where a ball bearing needs one. The last column is derived: radial section = (D − d) / 2, the wall thickness you are working with when you size the housing. No load rating and no limiting speed appears here — see the bearings index for why.

Outside diameter × overall size in millimetres, for the 5 smallest bores in this database. The full charts, one per type, are on the bearings index. Reading a row is what a machine designer does when the shaft is already fixed: the bore does not change, the housing bore does. Across the type boundary the last number changes meaning — it is a width above and a height below — so compare within a type, then decide whether the job wants a ball bearing, a tapered roller or a thrust bearing at all.