SKF6321/C3Open Heavy-Series Deep Groove Ball Bearing 105 x 225 x 49 mm, C3 Greater Clearance, 1 Pc

Product Description

What this part is

A single-row deep groove ball bearing in the 63 heavy dimension series — 105 mm bore, 225 mm outside diameter, 49 mm wide — open on both sides, with C3 greater-than-normal radial internal clearance. Deep groove ball bearings carry radial load plus axial load in either direction. At this size and section it is a large motor, crusher, mill drive, kiln fan and heavy gearbox bearing.

Decoding the designation

6 – single-row deep groove ball bearing3 – dimension series 63, the heavy section and width21 – bore code, 21 x 5 = 105 mm bore/C3 – radial internal clearance greater than normalNo closure suffix – open both sides; a 2Z would be steel shields, a 2RS1 contact rubber seals

What these specs mean in practice

Two specs decide this bearing. The heavy 63 section puts a 225 mm outside diameter and 49 mm width on a 105 mm shaft, where a medium 6221 uses 190 x 36 and a light 6021 just 160 x 26. Same bore, a great deal more capacity and life — which is why the 6321 turns up under real load on large motors and mill drives. The cost is size, weight and a lower speed ceiling.

The other is C3. Greater-than-normal clearance is what a large motor shaft needs: the inner ring goes on with a firm interference fit and the shaft runs hotter than the housing, so a normal-clearance bearing would lose its clearance to thermal growth, preload itself and overheat. Fit C3 where C3 came out. Equally, C3 in a cool, lightly loaded machine can run noisy — the mismatch fails both ways.

Being open, the bearing arrives without service grease and expects the housing to seal it and the machine to lubricate it. It is not a substitute for a shielded or sealed variant; in exchange it relubricates freely and runs in circulating or splash oil.

Published specifications

Bore: 105 mmOutside diameter: 225 mmWidth: 49 mmDimension series: 63 (heavy)Rows: 1Closure: open, both sidesInternal clearance: C3, greater than normalMaterial: through-hardened bearing steelEAN: 7316576619786

Quantity and configuration

Sold as 1 piece, one open bearing. No shields, no seals, no snap ring, no housing. New old stock: unused, from an opened carton marked Made in France.

Fitting notes

At 105 mm bore in a heavy section this is a heat-mount job — induction heater or oil bath to about 80 to 100 °C. A cold press at this size needs very high force and risks bruising the ball path. Load only the ring being fitted, never across the balls. For a rotating inner ring under normal to heavy load, k5 or k6 on the shaft with an H7 housing bore is the usual pairing, and C3 exists so that fit does not close the clearance up. Grease to roughly a third of the free internal space, or rely on the housing oil.

Interchange guidance

Genuine interchanges are same-envelope open 105 x 225 x 49 mm bearings with C3 clearance: FAG 6321-C3, NSK 6321C3, NTN 6321C3 and Koyo 6321C3. A plain 6321 (normal clearance) or a 6321/C4 (looser still) is a different clearance class; a 6321-2Z or 6321-M with a machined brass cage changes closure or cage. A 6221 or 6021 of the same bore is a lighter series and a physically smaller bearing — a related size, never a substitute.