30221T88-DB bearing: complete specifications & equivalents
The 30221T88-DB is a ISO 355 radial bearing sized 105 x 190 x 88 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 105 mm |
| Outer diameter D | 190 mm |
| Width B | 88 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 571 kN |
| Basic static load rating C0 | 710 kN |
| Fatigue load limit Pu | 80 kN |
| Reference speed (thermal) | 2200 rpm |
| Limiting speed (mechanical) | 3400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 9350 g |
| Manufacturer designation | SKF 30221T88/DB |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants |
| Last verified | 2026-09-29 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants) · extracted 2026-09-29
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & matched-db-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 3.465 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 42.5 mm |
| Smallest bore in matched-db-series | 35 mm |
| Largest outer diameter in matched-db-series | 480 mm |
| Width range across matched-db-series | 41.5–288 mm |
| Bore position in matched-db-series (smallest first) | 15 of 30 |
| Bore above smallest matched-db-series size | 70 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30221T88 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 30221T88-DB model number is decoded
Setting note for 30221T88-DB: the axial clearance is set at the factory by selective spacer grinding for the /DB execution; in service, re-checking end play after the first thermal cycle catches seating relaxation before it becomes roller skid. Clamp the assembled pair axially through the cones — never through the rollers — and verify the 88 mm overall width against the catalogue value before final torquing of the shaft nut.30221T88-DB (SKF 30221T88/DB) is the back-to-back (O) matched pair matched-set choice for a 105 mm shaft: a pair of tapered roller bearings whose combined envelope is 190×88 mm, delivered ready to mount with controlled internal clearance.Numbering ties the set to its envelope: base 30221T88 fixes the 105 mm bore and 190 mm OD of each bearing, the /DB suffix fixes the arrangement and setting, and the catalogue 88 mm width is the combined pair dimension. In the back-to-back (O) arrangement the load lines diverge toward the shaft axis, giving the pair a wide effective spread: 30221T88-DB resists overturning moments and tilting loads stiffly, which is why O-sets are preferred for gearbox output shafts and pinion supports. Catalogue mass 9350 g covers both bearings and the ground spacer of 30221T88-DB; keep the set complete — substituting one bearing or a non-ground spacer destroys the factory clearance. Journal and housing interface: the 105 mm bore takes a m6 shaft seat and the 190 mm outside diameter pairs with an H7 housing bore; the 88 mm width defines shoulder depth and the 9350 g mass is the dead load in thermal-growth calculations.
Typical equipment & failure modes
Common applications
- marine deck machinery shafts
- heavy industrial gearboxes and speed reducers
- large process pump and compressor shafts
- rolling-mill auxiliary drives
Known failure patterns
- uneven load sharing in a pair when spacer faces are not parallel to the bore
- roller large-end smearing against the cone rib after EP lubricant film failure
- cage pocket scoring when the bearing starts cold with grease of too-high base-oil viscosity
- rib-roller contact scoring from loss of the EP additive film
- mounting score marks when the cone is cocked over the shaft keyway or a burr
Selection pitfalls — read before you substitute
- Spacer faces must stay parallel within the set's own tolerance; a tilted spacer in 30221T88-DB concentrates reversing thrust on one bearing and shows up as one-sided raceway wear.
- Clamp the 30221T88-DB pair axially through the cones, never through the rollers; pressing force across the roller complement brinells the raceways of both bearings at once.
- Setting is built into 30221T88-DB; the classic field error is re-adjusting a matched pair as if it were two loose single bearings, which destroys the /DB clearance class.
- The 571/710 kN ratings are SKF catalogue 17000 values for this execution; SKF can revise internal geometry without changing the order number, so keep the catalogue version (PUB BU/P1 17000/1 EN, 2018) with the specification.
- Quote the full SKF 30221T88/DB designation when purchasing — base-number-only orders are ambiguous across executions and variants.
Frequently asked questions
What are the dimensions and catalogue data of 30221T88-DB?
The SKF 30221T88/DB is a matched pair of single-row tapered roller bearings in back-to-back (O) matched pair arrangement with 105 mm bore, 190 mm outer diameter and 88 mm overall width (4.134 × 7.48 × 3.465 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 571 kN, C0 710 kN, fatigue load limit Pu 80 kN, reference speed 2,200 r/min, limiting speed 3,400 r/min, mass about 9.35 kg.
What does the /DB suffix on 30221T88-DB mean?
The base 30221T88 is the ISO 355 single-row bearing; the /DB suffix marks the matched-set execution — the arrangement (back-to-back (O)), the ground spacer and the factory-set axial clearance class. A matched set cannot be assembled from loose single bearings; quote the full designation when ordering.
Are the C and C0 ratings of 30221T88-DB for one bearing or the pair?
They are for the complete matched pair: C 571 kN dynamic and C0 710 kN static already include load sharing between the two bearings. Do not halve them for single-bearing checks, and do not compare them directly with the single-row 30221T88 table values.
Can 30221T88-DB be adjusted like two loose tapered bearings?
No — the axial clearance is set at the factory by selective spacer grinding. Mounting work is limited to clean seats, correct fits (m6 on a rotating 105 mm shaft) and axial clamping through the cones; re-setting in the field destroys the matched clearance class.
When should a back-to-back (O) matched set be chosen?
Choose the back-to-back (O) set where moment stiffness dominates — pinion supports, gearbox output shafts, crane sheaves. The diverging load lines give the widest effective spread at the 105 mm bore.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants on 2026-09-29. Read our editorial & correction policy.