61844-ZZ bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NSK Rolling Bearings E1103 Part C) · extracted 2026-09-24

Cross references & equivalents

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 (diameter series 8 of ISO 15) 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. NSK catalogue order number: 6844ZZ (suffix ZZ), two non-contact steel shields, mapped here from the industry-neutral -ZZ spelling.

Typical equipment & failure modes

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.
• Never mix components between two 61844-ZZ units: rings, cage and balls are factory-matched and are not field-interchangeable, even between identical designations.
• The housing bore for the 270 mm OD should be round within IT7; an oval bore pinches the outer ring of 61844-ZZ and shows up later as two-point loaded raceway wear.
• NSK catalogues the shielded version as 6844ZZ — suffix ZZ, two non-contact steel shields. The industry-neutral page spelling is -ZZ; quote the NSK order number when buying through an NSK channel.
• The 220 mm bore places 61844 at the upper end of NSK's single-row deep-groove catalogue for the E1103 Part C extract; this is a heavy-engineering bearing where centrifugal force and cage inertia dominate the design envelope. NSK supplies a machined brass cage (suffix M) and expects oil lubrication with a defined relubrication interval — do not use catalogue grease speed figures for this size without an NSK engineering review.
• At 84 kN dynamic load rating (C) and 107 kN static (C0), 61844 is a heavy-load NSK bearing for industrial gearboxes and large conveyors; NSK expects a machined brass cage (suffix M) at this rating for shock duty, and the static C0 must be checked against any mounting or lifting loads.
• At 2900 g (2.9 kg), 61844 needs mechanical handling for mounting; NSK recommends induction heating the inner ring (max 120 °C) rather than pressing cold, and a lifting eye if the housing is pre-assembled.
• The 220×270×24 mm envelope of 61844 gives a D/d ratio of 1.23 and only 25.0 mm radial section height — this is an ultra-thin section in NSK's E1103 catalogue where shaft deflection and housing ovality directly load the ball-raceway contact; verify shaft stiffness (target deflection under 0.05 mm) before specifying it over a 62-series.
• The 84/107 kN load ratings, mass 2900 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6844ZZ on the 220×270×24 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61844 in a rated drive. NSK does not tabulate reference or limiting speeds in the E1103 Part C dimension tables used for this page — consult NSK's separate speed-rating tables before high-speed service.
• NSK does not recommend washing new shielded or sealed bearings; the rust-preventive film on open units is compatible with standard lithium greases and needs no removal unless the application demands a special fill.
• NSK supplies its sealed units pre-greased for general duty between roughly -10 and +110 °C; low-temperature, food-grade and high-temperature fills are special executions — ask at order time, because DDU/VV units are not designed to be opened and repacked.