71904 bearing: complete specifications & equivalents
The 71904 is a ISO 15 radial bearing sized 20 x 37 x 9 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 | 20 mm |
| Outer diameter D | 37 mm |
| Width B | 9 mm |
| Seal / shield | open |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | brass |
| Operating temperature | -40 to +150 °C |
| Mass (geometry estimate) | 35 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 71904 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & 71900-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.457 in |
| Width B | 0.354 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 8.5 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) | 1 of 17 |
| Bore above smallest 71900-series size | 0 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 71904 model number is decoded
In the 71900-series (ISO 15 diameter series 9) the last two digits encode the bore: 71904 carries bore code 04 = 20 mm. Outside diameter 37 mm and width 9 mm come from the ISO 15 boundary-dimensions general plan, shared with the 61904 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 20 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
- medical and lab spindles
- clutch and idler shafts
- semiconductor handling axes
- packaging machinery
Known failure patterns
- cage fracture from operation beyond the limiting speed with inadequate lubricant
- fretting corrosion on a loose shaft seat that lets the inner ring creep
- false brinelling from vibration while the shaft is stationary
- edge loading and early spalling from shaft deflection or housing misalignment
Selection pitfalls — read before you substitute
- At a 20 mm bore, shaft-seat finish and runout (target Ra ≤ 0.8 µm) govern angular-contact noise; a rough or out-of-round seat shows up as spindle runout before it shows as failure.
- The 719xx thin section (8.5 mm section height at 20 mm bore) trades capacity for compactness; stiff, accurately aligned seats are essential or edge loading will spall the raceway early.
- With a 8.5 mm radial section on a 20 mm bore, the 71904 ring has little stiffness of its own: it copies the seat geometry, so grind the 20 mm shaft in one setup and check roundness — an out-of-round journal distorts the thin inner ring and reappears as vibration at the 37 mm housing.
- The 40° contact angle (suffix C) raises axial capacity but lowers speed versus a 25° (E / A5) variant; for high-speed spindles specify the 25° version, for heavy thrust specify 40°.
- Angular-contact 71904 tolerates only minutes of misalignment; a deflected shaft or a tilted housing face edge-loads the asymmetric raceway and spalls it early — align the seats to better than 0.001 radian.
Frequently asked questions
What are the dimensions of a 71904 angular-contact bearing?
A 71904 single-row angular-contact ball bearing has a 20 mm bore, 37 mm outer diameter and 9 mm width (0.787 × 1.457 × 0.354 in), per ISO 15 boundary dimensions. It is an open bearing with a nominal 40° contact angle. Geometry-based estimated mass is about 35 g for a brass-cage unit; catalogue masses vary with cage and ball complement.
How does the 71904 bore code work?
The last two digits of 71904 are bore code 04, giving 04 × 5 = 20 mm bore. The 37 mm outside diameter and 9 mm width follow the ISO 15 diameter series, shared with the 61904 deep-groove envelope.
What is the contact angle of 71904?
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 71904 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.
What fits suit a thin-section 71904?
On a 20 mm shaft use the catalogue thin-section fit bands (typically j5/k5 shaft seats with H6/H7 housings) and keep shoulders minimal; because the 9 mm-wide rings are flexible, seat roundness and square abutment faces matter more than heavy interference for keeping the 8.5 mm section stable under load.
Reviewed & verified by the MPN Base engineering desk against source catalog iso15-ed4-geometry on 2026-09-24. Read our editorial & correction policy.