61811-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 61811-NTN model number is decoded

61811 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the extra-thin 618xx section (diameter series 8 of ISO 15), multiplying bore code 11 by five gives the 55 mm bore; the 72 mm outside diameter and 9 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 55 mm shaft under normal load, catalogue practice seats it on a k5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. 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

• At 55 mm bore, induction heating to roughly 80–100 °C is the clean mounting method; never exceed 120 °C, and hold 61811 against the shaft shoulder while it cools so the ring cannot creep back.
• Only 8.5 mm of radial section separates bore and OD on the 618xx series at 55 mm: ring flex from clamping or an oval housing bore transfers straight into raceway stress, so seat roundness matters more here than on a 6211.
• The open 61811-NTN has no lubricant retention: grease escapes and contaminants migrate straight into the 55×72×9 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
• Storage matters for open bearings: 61811-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.
• Vibration during standstill brinells the raceways of a 55 mm bearing at ball spacing; if the machine sits idle next to running equipment, turn the shaft over periodically or isolate the arrangement.
• The housing bore for the 72 mm OD should be round within IT7; an oval bore pinches the outer ring of 61811-NTN and shows up later as two-point loaded raceway wear.
• The open 61811 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.
• At 55 mm bore 61811 is in NTN's upper general-purpose range; the pressed-steel cage is standard but mid-section 63xx sizes at this bore can be ordered with a machined brass cage (suffix M) for heavy-shock or very-low-speed duty — confirm cage material with the NTN channel if the application sees impact loads.
• At 8700 r/min the grease limiting speed for 61811 covers most general-purpose industrial drives; the open or shielded execution can run continuously at this speed with standard lithium-soap grease.
• NTN rates 61811 at 9.75 kN dynamic (C) and 8.1 kN static (C0), 0.54 kN fatigue load limit Cu; this light-to-medium rating suits fractional-horsepower drives and instruments — for conveying or gearbox duty with shock loads, verify the equivalent dynamic load stays well below C.
• At 83 g, 61811 is light enough for hand assembly but should be pressed on with a fitting sleeve against the inner ring; do not strike the outer ring or cage with a hammer.
• The 55×72×9 mm envelope of 61811 gives a D/d ratio of 1.31 and only 8.5 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 9.75/8.1 kN load ratings, 0.54 kN fatigue load limit Cu NTN lists the grease limiting speed at 8700 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 83 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6811JR on the 55×72×9 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61811 in a rated drive.
• Standard catalogue stock of 61811 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.
• NTN's pressed-steel cage (no cage suffix) is the quiet standard for this size; for sustained running close to the limiting speed or for heavy shock duty, ask the NTN channel whether a machined-cage execution of 61811 is listed.