61800 Series Bearings
The ultra-thin series: on a 10 mm bore a 61800 is only 19 mm across, a radial section of 4.5 mm. It is the thinnest deep groove bearing in this database, and the one to reach for when the housing wall — not the load — is the constraint.
Ultra-thin serieswhere it sits and what it trades away
The 61800 series is the thinnest section in the deep groove family. 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 carries the lowest load of the five series here. 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 the other four series.
All 21 designationsISO 15 boundary dimensions, mm
| Designation | Bore code | d | D | B | r s min | Section (D − d)/2 |
|---|---|---|---|---|---|---|
| 61800 | 00 | 10 | 19 | 5 | 0.3 | 4.5 |
| 61801 | 01 | 12 | 21 | 5 | 0.3 | 4.5 |
| 61802 | 02 | 15 | 24 | 5 | 0.3 | 4.5 |
| 61803 | 03 | 17 | 26 | 5 | 0.3 | 4.5 |
| 61804 | 04 | 20 | 32 | 7 | 0.3 | 6 |
| 61805 | 05 | 25 | 37 | 7 | 0.3 | 6 |
| 61806 | 06 | 30 | 42 | 7 | 0.3 | 6 |
| 61807 | 07 | 35 | 47 | 7 | 0.3 | 6 |
| 61808 | 08 | 40 | 52 | 7 | 0.3 | 6 |
| 61809 | 09 | 45 | 58 | 7 | 0.3 | 6.5 |
| 61810 | 10 | 50 | 65 | 7 | 0.3 | 7.5 |
| 61811 | 11 | 55 | 72 | 9 | 0.3 | 8.5 |
| 61812 | 12 | 60 | 78 | 10 | 0.3 | 9 |
| 61813 | 13 | 65 | 85 | 10 | 0.6 | 10 |
| 61814 | 14 | 70 | 90 | 10 | 0.6 | 10 |
| 61815 | 15 | 75 | 95 | 10 | 0.6 | 10 |
| 61816 | 16 | 80 | 100 | 10 | 0.6 | 10 |
| 61817 | 17 | 85 | 110 | 13 | 1 | 12.5 |
| 61818 | 18 | 90 | 115 | 13 | 1 | 12.5 |
| 61819 | 19 | 95 | 120 | 13 | 1 | 12.5 |
| 61820 | 20 | 100 | 125 | 13 | 1 | 12.5 |
d = bore, D = outside diameter, B = width, r s min = minimum single chamfer dimension. All four are ISO 15 standard values and are the same for every manufacturer. 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.
Every series at one boresame shaft, different housing
| Series | Type | 10 mm bore | 12 mm bore | 15 mm bore | 17 mm bore | 20 mm bore |
|---|---|---|---|---|---|---|
| 61800 Series | Ultra-thin | 19 × 5 | 21 × 5 | 24 × 5 | 26 × 5 | 32 × 7 |
| 61900 Series | Thin | 22 × 6 | 24 × 6 | 28 × 7 | 30 × 7 | 37 × 9 |
| 6000 Series | Extra-light | 26 × 8 | 28 × 8 | 32 × 9 | 35 × 10 | 42 × 12 |
| 6200 Series | Light | 30 × 9 | 32 × 10 | 35 × 11 | 40 × 12 | 47 × 14 |
| 6300 Series | Medium | 35 × 11 | 37 × 12 | 42 × 13 | 47 × 14 | 52 × 15 |
Outside diameter × width in millimetres, for the five smallest bores in this batch. The full chart across all 21 bores and all 5 series is 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.
Frequently asked questionsreading a bearing designation
What is the difference between the 61800 and 61900 series?
Both are thin-section, and 61800 is the thinner of the two. On a 25 mm bore a 61805 is 37 mm across and 7 mm wide, and a 61905 is 42 × 9. The 61900 buys back ring section for 5 mm more housing bore — and with it real radial capacity.
Is the 61800 series the same as the 6800 series?
Yes — the same series under two naming conventions. 61800 is the form used by SKF and FAG; 6800 is the form used by NSK and several other makers. A 6814 and a 61814 are the same bearing: 70 mm bore, 90 mm outside diameter, 10 mm wide. Catalogues use both forms, so match on the dimensions as well as the number when you order.
How many sizes are in the 61800 series?
More than the 21 listed here. This batch covers 61800 to 61820, bores from 10 mm to 100 mm. Larger sizes exist — 61822, 61824, 61826 and beyond — and are not yet in this database.