61800 Series Deep Groove Ball Bearings

The second-thinnest section here, and the thinnest that most catalogues actually stock: 4.5 mm of radial section on a 10 mm bore, against 2.5 mm for the 61700 of the same bore. It is what fits when the housing wall, not the load, is the binding constraint: instruments, encoders, lightly loaded spindles.

The 61800 series is the second-thinnest section tabulated here, one rung above the 61700. Its designation carries an 18 where a 6000 carries a 0, and the difference that makes is large: at the same bore the outside diameter is roughly three-quarters of a 6000's. A 10 mm shaft takes a 61800 of 19 mm outside diameter and 5 mm width, where the same shaft takes a 6000 of 26 × 8 — 7 mm less housing bore, which in a tight design is the difference between fitting and not fitting.

That thinness has a cost, and it is the same trade as everywhere else in this sub-library: less ring section means less room for rolling elements and a shallower raceway, so a 61800 has the smallest ring section here bar one — only the 61700 is smaller. The series is not selected for its capacity. It is selected by instruments, encoders, small spindles and light mechanisms where the bearing locates a shaft rather than carries a load, and where a few millimetres of housing wall decide the design.

The series runs from 61800 (10 mm bore, 19 mm outside diameter, 5 mm wide) to 61820 (100 mm bore, 125 mm outside diameter, 13 mm wide) in the 21 designations tabulated here. Notice how flat that progression is: the outside diameter grows from 19 to 125 mm across the range, but the radial section only grows from 4.5 mm to 12.5 mm. A 61820 is not a heavy bearing that happens to be large — it is a thin one that happens to be large.

Every designation in the table below links to its own page with the ISO 15 dimensions, the bore-code arithmetic, the ISO 5753-1 clearance ranges for its bore, and the same-bore comparison against every other series.

This series runs from a 10 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, 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. 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.