61840-NTN bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)) · extracted 2026-09-25

Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.

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 61840-NTN model number is decoded

In the 61800-series (diameter series 8 of ISO 15) the last two digits encode the bore: 61840 carries bore code 40 = 200 mm. Outside diameter 250 mm and width 24 mm come from the ISO 15 boundary-dimensions general plan. With no seal suffix the bearing is open: no shields or seals are fitted and lubrication is supplied by the application. For normal-load mounting with a rotating inner ring on a 200 mm shaft, typical catalogue practice is a m6 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. In the NTN catalogue this open execution carries the bare designation; protected variants are ordered separately with suffixes ZZ (shields), LLB/LLF (non-contact seals), LLH (low-torque contact seal) and LLU (contact seal).

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Mount this 200 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.
• Only 25.0 mm of radial section separates bore and OD on the 618xx series at 200 mm: ring flex from clamping or an oval housing bore transfers straight into raceway stress, so seat roundness matters more here than on a 6240.
• The open 61840-NTN has no lubricant retention: grease escapes and contaminants migrate straight into the 200×250×24 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
• Storage matters for open bearings: 61840-NTN leaves the factory with rust preventive only, so clean it and apply the service grease at assembly even if the rings look oily from the wrapper.
• Do not quieten a noisy bearing by preloading it: the 61800-series is a deep-groove design, not angular-contact; axial preload raises temperature and shortens grease life.
• Deep-groove ball bearings tolerate only minutes of misalignment; if the 250 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 61840-NTN.
• The open 61840 has no integral sealing; in the NTN 2203 catalogue the protected variants carry suffixes ZZ (non-contact steel shields), LLB/LLF (non-contact rubber seals), LLU (contact rubber seals) and LLH (a low-torque contact seal with higher speed capability than LLU). A JR or JRX suffix (printed for some thin-section sizes) denotes a pressed-steel cage, not a seal.
• The 200 mm bore places 61840 in NTN's large-size range; at these diameters the pressed-steel cage is speed-limited and NTN commonly supplies a machined brass cage (suffix M) as an option. Verify cage material and relubrication interval with the NTN distributor, and do not extrapolate small-bore speed ratings to this size.
• NTN lists the grease limiting speed at 2300 r/min for 61840; this is a large or heavy-section size where centrifugal force and cage inertia cap the speed — for higher shaft speeds either step to a smaller bearing on the same bore or consult NTN for an oil-lubricated, machined-cage variant.
• At 82 kN dynamic load rating (C) and 91.5 kN static (C0), 4.05 kN fatigue load limit Cu, 61840 is a heavy-load bearing for industrial gearboxes and large conveyors; NTN 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 2730 g (2.7 kg), 61840 needs mechanical handling for mounting; NTN recommends induction heating the inner ring (max 120 °C) rather than pressing cold, and a lifting eye if the housing is pre-assembled.
• The 200×250×24 mm envelope of 61840 gives a D/d ratio of 1.25 and only 25.0 mm radial section height — this is an ultra-thin section 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 82/91.5 kN load ratings, 4.05 kN fatigue load limit Cu NTN lists the grease limiting speed at 2300 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 2730 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6840 on the 200×250×24 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61840 in a rated drive.
• Standard catalogue stock of 61840 is the general-purpose execution; for low-noise motor duty NTN offers low-torque seal and special-grease variants in this size class, which are separate order numbers.
• Factory-fill grease in NTN sealed units is a general-duty lithium-soap grease; food-grade, low-temperature and high-temperature fills are request options at order time, because LLU/LLB units are not meant to be opened and re-greased in the field.