71918 bearing: complete specifications & equivalents
The 71918 is a ISO 15 radial bearing sized 90 x 125 x 18 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | Generic ISO interchange (unbranded) |
| Bore diameter d | 90 mm |
| Outer diameter D | 125 mm |
| Width B | 18 mm |
| Seal / shield | open |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | brass |
| Operating temperature | -40 to +150 °C |
| Mass (geometry estimate) | 543 g |
| Standard | ISO 15 |
| Catalog version | iso15-ed4-geometry |
| Last verified | 2026-09-24 |
Source: ISO 15 boundary-dimensions standard · extracted 2026-09-24
Standard-interchange bearing: dimensions per ISO 15; CN clearance, P0 tolerance and a stamped-steel cage are catalogue defaults unless the supplier states otherwise, and mass is a geometry-derived estimate. Brand catalogue load ratings and limiting speeds for 71918 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & 71900-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 4.921 in |
| Width B | 0.709 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 17.5 mm |
| Smallest bore in 71900-series | 20 mm |
| Largest outer diameter in 71900-series | 140 mm |
| Width range across 71900-series | 9–20 mm |
| Bore position in 71900-series (smallest first) | 15 of 17 |
| Bore above smallest 71900-series size | 70 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 71918 model number is decoded
In the 71900-series (ISO 15 diameter series 9) the last two digits encode the bore: 71918 carries bore code 18 = 90 mm. Outside diameter 125 mm and width 18 mm come from the ISO 15 boundary-dimensions general plan, shared with the 61918 deep-groove envelope. The '7' prefix marks a single-row angular-contact design with an asymmetric raceway and a nominal 40° contact angle (suffix C); a higher-angle variant carries more axial load, a 25° (E / A5) variant runs faster. For combined radial and axial load with a rotating inner ring on a 90 mm shaft, specify a k5 shaft seat with an H7 housing bore — verify against the load direction and magnitude, and pair two units (DB or DF) for bidirectional thrust.
Typical equipment & failure modes
Common applications
- semiconductor handling axes
- packaging machinery
- robotics joint arms
- precision rotary tables
Known failure patterns
- preload loss after a paired set runs loose, letting the balls skid and smear the raceway
- raceway smearing under marginal lubrication at start-up before oil climb reaches the contact
- cage fracture from operation beyond the limiting speed with inadequate lubricant
- fretting corrosion on a loose shaft seat that lets the inner ring creep
Selection pitfalls — read before you substitute
- Mount this 90 mm bore angular-contact pair by heating the inner rings (induction heater, max 120 °C) and clocking both faces; never drive a pair home through the outer rings.
- The 719xx thin section (17.5 mm section height at 90 mm bore) trades capacity for compactness; stiff, accurately aligned seats are essential or edge loading will spall the raceway early.
- The 125 mm outer ring of 71918 is only 17.5 mm thick over the raceway: the housing bore must be round and rigid and the abutments square, because edge stress on a thin section spalls the 18 mm-wide raceway long before the load rating is reached.
- Assign fits by which ring rotates: an interference shaft fit for a rotating inner ring; if the outer ring rotates instead, reverse the logic — a loose rotating ring creeps and frets its seat.
- A single 71918 angular-contact bearing takes axial load in ONE direction only — for bidirectional thrust, mount a matched pair (DB back-to-back or DF face-to-face), never rely on one row.
Frequently asked questions
What are the dimensions of a 71918 angular-contact bearing?
A 71918 single-row angular-contact ball bearing has a 90 mm bore, 125 mm outer diameter and 18 mm width (3.543 × 4.921 × 0.709 in), per ISO 15 boundary dimensions. It is an open bearing with a nominal 40° contact angle. Geometry-based estimated mass is about 543 g for a brass-cage unit; catalogue masses vary with cage and ball complement.
How does the 71918 bore code work?
The last two digits of 71918 are bore code 18, giving 18 × 5 = 90 mm bore. The 125 mm outside diameter and 18 mm width follow the ISO 15 diameter series, shared with the 61918 deep-groove envelope.
What is the contact angle of 71918?
The nominal contact angle is 40° (suffix C): a higher angle carries more axial load but limits speed. A 25° (suffix E or A5) variant runs faster and is preferred for high-speed spindles; a 15° (suffix C7) version exists for very-high-speed duty. Confirm the angle and ball complement in the supplier catalogue.
Can a single 71918 take axial load in both directions?
No. A single-row angular-contact bearing carries axial load in one direction only. For bidirectional thrust, mount a matched pair — DB (back-to-back) for a rigid, moment-resisting arrangement with preload class light (L) for speed or heavy (H) for stiffness, DF (face-to-face) for thermal expansion tolerance, or DT (tandem) to share one-direction load.
Why is the 71918 ring section so thin?
The 718/719 dimension series save radial space: at a 90 mm bore the 71918 envelope is 90×125×18 mm with a 17.5 mm radial section. That trades absolute load capacity for compactness and weight in robotics, medical and rotary-table axes — capacity per mm of section is high, but the ratings sit below a 72-series bearing of the same bore.
Reviewed & verified by the MPN Base engineering desk against source catalog iso15-ed4-geometry on 2026-09-24. Read our editorial & correction policy.