30300 Series Tapered Roller Bearings

The medium tapered series: same bore ladder as the 30200, one step larger across and wider. A 30304 is 52 mm across and 16.25 mm wide on a 20 mm bore, against 47 × 15.25 for the 30204 of the same bore. That extra envelope is what buys load capacity, so a 30300 is what a gearbox shaft steps up to when the 30200 is running out of rating. The width triples read the same way: B inner ring, C outer ring, T assembled.

The 30300 is to the 30200 what the 6300 is to the 6200: the same shaft, a larger bearing around it. The step is not small. At a 20 mm bore the outside diameter goes from 47 to 52 mm and the total width T from 15.25 to 16.25 mm; at a 100 mm bore the pair is 180 × 37 against 215 × 51.5 mm. The last of those numbers is worth reading twice: at the top of the two series the medium bearing is 14.5 mm thicker in the axial direction, which is a mounting change, not a rounding error.

That is the whole trade of a dimension series, and it is the same trade as in the ball family: more envelope means more room for rollers, a larger rolling-element circle and a stiffer shaft support, at the price of the housing and the mass. So a 30300 is what a gearbox shaft steps up to when the 30200 has run out of load capacity and the shaft diameter is already fixed by the design — which is the usual situation, because the shaft is sized by torque and deflection long before the bearing is chosen.

The three widths read exactly as they do in the light series. B is the inner ring, C the outer ring and T the assembled bearing, with B + C exceeding T because the rings interpenetrate: on a 30320 they are 47, 39 and 51.5 mm. The bore-code rule and the designation structure are unchanged — 30302 is type 3, dimension series 03, bore code 02, and the same caveat as in the light series applies at 02 and 03, where the standard's own series table begins at bore code 04 while the catalogues carry the two smaller sizes.

The series tabulated here runs from 30302 (15 mm bore, 42 mm outside diameter, 14.25 mm total width) to 30320 (100 mm bore, 215 mm outside diameter, 51.5 mm total width). Every designation links to its own page with the ISO 355 dimensions, the bore-code arithmetic, the same-bore comparison across every bearing type, and the note on why no radial clearance group applies to a tapered roller bearing.

This series runs from a 15 mm to a 100 mm bore. The sub-library as a whole reaches 300 mm of bore, and the widest single bearing in it is a 6360, 620 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. The 6 series whose type has no bore are not rows here: they are indexed by the shaft they run on, and their chart is above.