SKF6404Open Extra-Heavy Deep Groove Ball Bearings 20 x 72 x 19 mm, 64 Series, Normal Clearance, 2 Pcs

Product Description

What this part is

Two single-row deep groove ball bearings from the 64 extra-heavy dimension series — 20 mm bore, 72 mm outside diameter, 19 mm wide, open on both sides. Deep groove ball bearings carry radial load plus axial load in either direction. The 64 series is unusual and worth understanding: it wraps a very large outside diameter and ball set around a small bore, which is how a 20 mm shaft ends up carrying loads normally reserved for a much bigger bearing.

Decoding the designation

6 – single-row deep groove ball bearing4 – dimension series 64, the extra-heavy section04 – bore code, 04 x 5 = 20 mm boreNo closure suffix – open both sides; a 2Z would be steel shields, a 2RS1 contact rubber sealsNo clearance suffix – normal (CN) radial internal clearance

What these specs mean in practice

Compare the family on a 20 mm shaft: a 6204 is 47 mm outside diameter and 14 mm wide, a 6304 is 52 x 15, and this 6404 is 72 x 19. Same bore, far more bearing. That buys a large jump in radial capacity and life where the shaft cannot be made bigger but the load will not go away — small heavily loaded gearboxes, idlers, tensioners and machine tool accessories. What it costs is a large housing bore, more weight and a lower speed ceiling than the lighter series.

Because these are open, they arrive without service grease. Each must be lubricated on assembly and sealed by the housing, and an open bearing is not a substitute for a shielded or sealed one, which arrives pre-greased and closed. In return, an open bearing relubricates freely and will run in circulating or splash oil.

Published specifications

Bore: 20 mmOutside diameter: 72 mmWidth: 19 mmDimension series: 64 (extra heavy)Rows: 1Closure: open, both sidesInternal clearance: normal (CN)Material: through-hardened bearing steelEAN: 7316577738608

Quantity and configuration

Sold as one lot of 2 Pcs — two individual open bearings, not a matched or preloaded pair. No shields, no seals, no snap rings.

Fitting notes

Press or heat-mount on the inner ring only and never let mounting force cross the balls. For a rotating inner ring under normal load, j5 to k5 on a 20 mm shaft with an H7 housing bore is the usual pairing. Fill roughly a third of the free internal space with grease, or rely on the housing oil, and provide housing sealing — the bearings have none of their own.

Interchange guidance

Genuine interchanges are same-envelope 20 x 72 x 19 mm 64-series bearings: FAG 6404, NSK 6404, NTN 6404, Koyo 6404 and Nachi 6404. A 6204 or 6304 shares the bore only and is a much smaller, lower-capacity bearing — a related size, never a substitute. A 6404-2Z or 6404-2RS1 is the same envelope with a different closure.