1200 Series Self-aligning Ball Bearings

The light self-aligning series, and the one whose envelope is already familiar from another page in this library: a 1204 is 20 × 47 × 14 mm, the same three numbers as a 6204 of the same bore. What differs is inside the rings — two rows of balls running on a single sphered outer raceway, so the bearing takes up angular misalignment between shaft and housing that the 6204 would carry as edge loading. The trade is axial: the contact angle is small and the balls do not conform closely to the raceways, so this is not a bearing to press axially. The 12 is not a two-digit series number of its own: it is the type code 1 and the diameter series 2 run together, with the width series 0 left unwritten — the note above the table spells the two digits out.

The 12 at the front is not a series number. A 1204 is the self-aligning type code 1, the diameter series 2 and the bore code 04 — the same three fields a 6204 has, with 1 in place of 6. The width series is 0 and is never written, so the digit you see between the type code and the bore code is a diameter series on its own: the 2 in 1204, the same rung a 6204's middle digit names, and that is the whole reason the two families share their outside diameters. The bore code still reads exactly as it does everywhere else — 00, 01, 02 and 03 are 10, 12, 15 and 17 mm, and from 04 upwards the code multiplies by five.

Why the 1200 and the 6200 have the same numbers. The second digit of 12 is 2, the same diameter series a 6204's middle digit names. So the two families sit on the same rung of the same outside-diameter ladder, and one table is a row-for-row copy of the other: 1204 is 20 × 47 × 14 mm and 6204 is 20 × 47 × 14 mm, all the way down. That cuts both ways in practice — a housing bored for a 6204 will take a 1204, and a 1204 ordered as a replacement arrives at the same size and a different bearing.

What the type buys, and what it costs. The outer ring carries a single sphered raceway and the inner ring two rows of balls, so the shaft may sit at a small angle to the housing without the bearing binding. That is what a self-aligning bearing is for: a long shaft that sags under load, a housing bored in two halves, a welded frame that springs when it is bolted down. The price is axial capacity — two rows on a spherical seat carry very little along the shaft — and the type is not the one to reach for when the load runs that way.

Every designation in the table below links to its own page with the ISO 15 dimensions, the bore-code arithmetic, the same-bore comparison against every other series and type, and the reason this type carries no radial clearance table here.

This series runs from a 10 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, B = width. All of them are ISO 15 standard values and are the same for every manufacturer. r s min is the minimum single chamfer dimension the plan gives; its matching maximum is in ISO 582, which is why the column says “min” and not an equality. 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.