Which standard do these bearings follow?
ISO 12240-1 covers the size, not the name.
The standard specifies dimension series, dimensions, tolerances and radial internal clearance for radial spherical plain bearings. Designations, load ratings and life calculations are outside it, so each maker writes its own. The dimension series it lists are K, E, G and W. Inch-size bearings (GEZ) follow a separate ANSI/ABMA standard.
The practical consequence: two bearings from the same dimension series and bore should fit the same shaft and housing, but their load ratings and life figures are each maker's own (Q1-03).
What does a dimension series actually fix?
For a given bore d, a series fixes the outside diameter D, the width B and, with them, the ball diameter dk and the ring widths. Different series are different packages around the same shaft: a series with a larger D and B gives a larger sliding area and costs more space.
A made-up pair shows what that means. Take two series for a 30 mm bore, one with dk = 40 mm and outer ring width C = 22 mm, the other with dk = 44 mm and C = 28 mm (illustrative numbers, not catalogue parts). The ball is carried by the outer ring, so the projected sliding area is roughly dk × C: 880 mm² against 1,232 mm², a ratio of 1.4. At the same 30 kN radial load, the contact pressure p = P ÷ (dk × C) is 34.1 MPa in the first and 24.4 MPa in the second, about 29 % lower. That is why "same bore" does not mean "same capacity", and why the series, not the bore, is the first thing to match when you compare two parts.
What do the series letters mean?
The letter groups below are how makers name what they build on those series.
| Letters | What it usually is |
|---|---|
| GE | The common radial spherical plain bearing, metric sizes, single-split outer ring. The baseline type |
| GEZ | The same idea in inch sizes |
| GEG | A wider inner ring and a larger outside diameter than GE |
| GEH | A heavy-duty type with higher load capacity than GE. Check the dimensions: a larger-diameter, wider series that one maker calls GEH may be listed as GEG by another |
| GEEW | An outer ring as GE, with an inner ring that extends on both sides |
| GEEM | As GEEW, with a width that equals the bore diameter |
| GEM | An extended inner ring of non-standard width, otherwise the same dimensions as GE |
The reliable test is the dimension table, not the letters. Read bore, outside diameter and width off both catalogues; if all three match, the two parts belong to the same dimension series whatever each calls it. If a part carries a letter group not listed here, read the maker's table before assuming what it means.
What do the suffixes mean?
They give details of the same series, and they also vary by maker.
| Suffix | Meaning |
|---|---|
| E | Single-split outer ring |
| S | Lubrication groove and holes in the inner and outer rings |
| ES | Both of the above: a split outer ring with a lubrication groove and holes |
| 2RS | Rubber seals on both sides |
| C | A PTFE-based maintenance-free sliding surface. Which system differs by maker: one widely used naming scheme uses C for steel/PTFE sintered bronze, while other catalogues use GE..C for steel/PTFE fabric |
| TX | Steel/PTFE fabric sliding surface, maintenance-free (in that naming scheme) |
| F | Steel/PTFE fibre-reinforced polymer sliding surface, maintenance-free (same naming) |
Because C is not used the same way everywhere, check what the maker's table says it is before you decide whether the bearing may be greased.
A bearing such as "GE..ES 2RS" is a radial spherical plain bearing with steel/steel sliding surfaces that needs maintenance, like GE..ES but with integrated seals. Makers typically offer open, 2RS sealed (for dust and contamination) and reinforced-seal versions.
Which of these can be greased?
Steel/steel types need it. Steel/PTFE sintered bronze (C) and steel/PTFE fabric (TX) bearings are self-lubricating and must not be lubricated: the PTFE transfers to the ball as a thin film, and added grease disturbs that film. The steel/PTFE fibre-reinforced (F) type is also maintenance-free, but occasional relubrication helps maximise life, and it has lubrication facilities for that. See Q1-02 for how to choose between the two kinds, and Q1-08 for steel/steel lubrication.
How do you read a part number?
From the front: series letters, then the bore, then the details. In the metric ranges the number is the bore in millimetres, so GEG30ES has a 30 mm bore, and GEG30ES 2RS is the same with seals on both sides. Spaces and hyphens ("GE 30 ES-2RS") carry no meaning. The code answers three questions.
| You want to know | Where it is written |
|---|---|
| Does it fit the shaft and housing? | Bore number plus series letters, then the maker's table of d, D and B |
| What is the sliding surface, and may I grease it? | The suffix (C, TX, F or none), confirmed in the maker's table |
| Is it sealed? | 2RS or the maker's seal code; an open ES bearing has no seals |
Check any unfamiliar letters against the maker's own table, since the standard does not define the names.