61844-ZZ bearing: complete specifications & equivalents
The 61844-ZZ is a ISO 15 radial bearing sized 220 x 270 x 24 mm (bore x OD x width) with ZZ sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NSK |
| Bore diameter d | 220 mm |
| Outer diameter D | 270 mm |
| Width B | 24 mm |
| Material | GCr15 |
| Seal / shield | ZZ |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 84 kN |
| Basic static load rating C0 | 107 kN |
| Mass | 2900 g |
| Manufacturer designation | NSK 6844ZZ |
| Standard | ISO 15 |
| Catalog version | NSK Rolling Bearings E1103 Part C |
| Last verified | 2026-09-24 |
Source: catalog reference (NSK Rolling Bearings E1103 Part C) · extracted 2026-09-24
Dimensions in inches & 61800-series range
| Bore d | 8.661 in |
|---|---|
| Outer diameter D | 10.63 in |
| Width B | 0.945 in |
| ISO bore code | 44 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 61800-series | 10 mm |
| Largest outer diameter in 61800-series | 420 mm |
| Width range across 61800-series | 5–38 mm |
| Bore position in 61800-series (smallest first) | 33 of 39 |
| Bore above smallest 61800-series size | 210 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61844 | ISO-INTERCHANGE | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | ISO 15 envelope interchange; NSK suffix 6844ZZ maps to industry-neutral ZZ. Verify seal design, grease and speed rating per brand catalogue. |
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 61844-ZZ model number is decoded
In the 61800-series (ISO 15 diameter series 8) the last two digits encode the bore: 61844 carries bore code 44 = 220 mm. Outside diameter 270 mm and width 24 mm come from the ISO 15 boundary-dimensions general plan. Suffix -ZZ denotes two non-contact metallic shields; they retain grease and block coarse debris but are not liquid-tight. For normal-load mounting with a rotating inner ring on a 220 mm shaft, typical catalogue practice is a m6 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude.
Typical equipment & failure modes
Common applications
- textile machinery
- packaging machinery
- space-constrained gearboxes
- clutch and transmission assemblies
Known failure patterns
- fine-particle abrasion when non-contact shields let dust past in dirty duty
- grease aging in the shield-for-life cavity with no relubrication path
- fretting corrosion on a loose shaft seat
- cage damage from operation beyond the limiting speed
Selection pitfalls — read before you substitute
- Mount this 220 mm bore bearing by heating the inner ring (induction heater, max 120 °C) — never drive it home through the outer ring or balls, that brinells the raceways.
- The 618xx thin section at 220 mm bore has only a 25.0 mm radial section height: it saves space but is highly sensitive to misalignment, shaft deflection and shock loads — verify shaft stiffness before choosing it over a 6244.
- ZZ shields are non-contact: 61844-ZZ blocks chips and coarse dust but is not waterproof — do not install it expecting a pressure-wash seal, step up to 61844-2RS for that.
- Shielded 61844-ZZ units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 270 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 61844-ZZ.
- NSK catalogues the shielded version as 6844ZZ — suffix ZZ, two non-contact steel shields; the industry-neutral page spelling is -ZZ. Quote the NSK designation when ordering.
- The 84/107 kN ratings, mass 2900 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6844ZZ; this seal/size combination has no counterpart in the SKF 17000 extract used elsewhere on this site, so the page rests on a single manufacturer source — internal geometry and ratings legitimately differ between brands, so re-verify before substituting in a rated drive.
Frequently asked questions
What are the dimensions of a 61844-ZZ bearing?
A 61844-ZZ deep-groove ball bearing has a 220 mm bore, 270 mm outer diameter and 24 mm width (8.661 × 10.63 × 0.945 in), per ISO 15 boundary dimensions. It is fitted with two non-contact metallic shields.
How does the 61844 bore code work?
The last two digits of 61844 are bore code 44, giving 44 × 5 = 220 mm bore. The 270 mm outside diameter and 24 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the ZZ suffix on 61844-ZZ mean?
ZZ means two non-contact sheet-metal shields, one each side. They retain factory grease and block coarse particles with little friction, but do not seal against liquids, fine dust or pressure washing.
How does the 61800 compare with other series at the same 220 mm bore?
618 is an extra-thin section: 270×24 mm, only 25.0 mm radial section at 220 mm bore, far smaller than a 6244, for space-limited layouts at the cost of load rating and misalignment tolerance.
What is the NSK designation and catalogue data for 61844-ZZ?
In the NSK Rolling Bearings catalogue (E1103 Part C) this size is listed as 6844ZZ — two non-contact steel shields (NSK suffix ZZ), 220×270×24 mm per ISO 15. Quoted values: C 84 kN, C0 107 kN, mass 2900 g. The industry-neutral page spelling 61844-ZZ follows the seal-suffix convention used across this site, not NSK order-number spelling. Reference and limiting speeds are not tabulated in the E1103 dimension tables used here; consult NSK speed tables before high-speed service.
Reviewed & verified by the MPN Base engineering desk against source catalog NSK Rolling Bearings E1103 Part C on 2026-09-24. Read our editorial & correction policy.