6318-ZZ-NSK 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 6318-ZZ-NSK model number is decoded

In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6318 carries bore code 18 = 90 mm. Outside diameter 190 mm and width 43 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 90 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. NSK catalogue order number: 6318ZZ (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

• At 90 mm bore the ring mass is significant: heat 6318 on an induction heater (max 120 °C), never over an open flame, and plan puller access or a withdrawal sleeve now for the day it has to come off again.
• The 63xx medium section at 90 mm bore gains dynamic rating through larger rolling elements on a 190 mm OD; the penalty is mass and a lower limiting speed than the 6218 — do not specify it for speed-critical shafts.
• ZZ shields are non-contact: 6318-ZZ-NSK blocks chips and coarse dust but is not waterproof — do not install it expecting a pressure-wash seal, step up to 6318-2RS for that.
• Shielded 6318-ZZ-NSK units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
• Grease compatibility is not guaranteed between fills: mixing lithium and polyurea thickeners in a 6300-series position can soften the mixture and leak — clean out the old fill before switching grease types.
• Suffixes stack in a defined order — clearance follows the seal code, e.g. 6318-ZZ-NSK-C3. No clearance suffix means normal CN clearance.
• NSK catalogues the shielded version as 6318ZZ — 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.
• At 90 mm bore 6318 is in NSK's medium industrial range; the pressed-steel cage is standard, but large-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 NSK channel if the application sees impact loads.
• NSK rates 6318 at 157 kN dynamic (C) and 107 kN static (C0); this heavy-load rating is at the upper end of the E1103 Part C single-row deep-groove extract — NSK supplies a machined brass cage (suffix M) and expects an application review, because catalogue L10 life alone does not capture shock and misalignment loads at this rating.
• At 4980 g (5.0 kg), 6318 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 90×190×43 mm envelope of 6318 gives a D/d ratio of 2.11 and 50.0 mm radial section height — a heavy NSK section built for high-load, lower-speed duty; specifying it in a high-rpm motor generates excess heat and shortens grease life, so prefer a 62/63-series there.
• The 157/107 kN load ratings, mass 4980 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6318ZZ on the 90×190×43 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6318 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.
• When replacing a failed unit, inspect the shaft and housing seats before fitting the new 6318 — a new bearing pressed onto a worn or oval seat reproduces the original failure mode in a fraction of its expected life.
• 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.