SKF inner rings for needle bearings: IR and LR

In IR 12X15X16, the three numbers are the bore of the ring, its outside diameter and its width, in millimetres. The outside diameter is what ties it to the bearing: it must match the diameter under the needles of the bearing that goes over it. IR 7X10X10.5 shows that the width may carry decimals, and they must be copied.

LR 15X18X12.5 belongs to another series of rings, with the same three dimensions in the code and another finish. A block of letters at the end, as in IR 40X50X20 IS1, marks a particular execution. For the same bore and outside diameter there are usually several widths, so the first two dimensions are not enough.

The ring is chosen from the bearing, not the other way round. First the needle roller bearing is identified, with its diameter under the needles and its width; then the ring with that outside diameter and an equal or greater width is found. A ring wider than the bearing lets the shaft move slightly lengthwise without the needles leaving the raceway.

The fit on the shaft must be firm. A ring that turns on the shaft wears it and heats the assembly. If the shaft already shows marks from the previous ring, measure it before ordering: the seat may need to be restored. During mounting, the ring is pushed on or heated; it is not struck on the edge.

Send us the complete designation and the quantity. If you do not have it, give us the designation of the needle roller bearing it works with and the actual shaft diameter: with that the possible rings are found. With no code at all, measure bore, outside diameter and width with a micrometer. Saying whether the shaft moves lengthwise in service helps define the width.