The dynamic load rating of 29.5 kN characterises this bearing. The static load rating is 15 kN. The limiting speed is 12000 rpm. Standard bearing steel and normal radial clearance make up the base version of the series: no special demand on sealing, material or thermal expansion, and in return the widest field of use in general mechanical engineering.
In a deep groove ball bearing a single row of balls runs in one deep raceway groove in each of the inner and outer ring, the curvature radius of which is only slightly larger than the ball radius. Both consequences follow from this close conformity: a small contact area that widens into an ellipse under load, with correspondingly low rolling friction, and the ability to transmit axial force in both directions through the groove shoulders.
That axial capability is tied to the contact angle which establishes itself under axial load — it therefore depends on the clearance remaining in the mounted state and is not a fixed property of the size. The bearing is non-separable: both rings and the ball set form one unit, which is why the mounting force must always be applied through whichever ring receives the interference fit, and never through the rolling contact.
The open form brings no sealing element of its own; sealing, initial filling and relubrication rest with the design, which in exchange is free to use oil, oil-mist or circulating lubrication and to carry heat away with the lubricant. Through-hardened standard bearing steel provides hardness, dimensional accuracy and fatigue strength across the usual operating temperature range; whether a position may be run above it is to be taken from the designation and the dimensional stabilisation data.
The normal radial clearance is matched to one interference-fitted ring and a moderate temperature difference between inner and outer ring; what governs is always the residual clearance in the mounted, warm running state, not the clearance as delivered. Because no sealing element isolates the bearing position, the cleanliness and lubricant supply of the surroundings decide the achievable service life in practice more often than material fatigue does.
ManufacturerNTN
Bearing typeDeep-groove ball bearings
Bore d30 mm
Outer Ø D72 mm
Width B19 mm
Dyn. load C29.5 kN
Stat. load C₀15 kN
Fatigue limit Pu1.14 kN
Limiting speed12,000 min⁻¹
Reference speed6,600 min⁻¹
Weight0.345 kg
Sealsnone (open bearing)
Clearancenormal radial internal clearance
Cagepressed steel cage
Materialstandard bearing steel
Tolerancetolerance class P0/PN (ABEC 1)
Bore typecylindrical bore
€8.01/ pc
incl. VAT, plus shipping · price drops with quantity
In stock
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QtyUnit priceDisc.
1 – 4€8.01—
5 – 9€7.77−3 %
10 – 24€7.61−5 %
25 – 49€7.37−8 %
50 – 99€7.21−10 %
4 more for −3% volume discount
From 100 pcs: price and lead time on request – subject to review.
Total (1 pc)€8.01
NTN 6306 Kugellager (30x72x19)
— 30 x 72 x 19 mm
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Same dimensions means the same bearing type and matching main dimensions (d × D × B). Sealing, cage, internal clearance and execution (e.g. material, precision, grease fill) are encoded in the suffix and may differ — please check before ordering. Equivalent additionally means the same sealing, internal clearance and tolerance class; the cage and other suffix features (e.g. lubrication groove) may differ.
