Single-Row Angular Contact Ball Bearing 105 x 160 x 26 mm, 30 Degree Contact Angle, Slim 70-Series Section, Open

What this part is:
A single-row angular contact ball bearing in the 7000 (ISO dimension series 10) envelope: 105 mm bore, 160 mm outside diameter, 26 mm width. Large bore, thin ring section, open on both sides. This is the size range where spindle and rotary-table designers are fighting for radial space and cannot use a chunkier 72- or 73-series bearing.

Decoding the designation:
70 – single-row angular contact ball bearing, dimension series 10 (extra-light section).21 – bore code; 21 x 5 = 105 mm bore.A – 30° nominal contact angle in NSK’s scheme. The 15° version of the same envelope is 7021C.DB (from the carton designation 7021ADBC7) – back-to-back duplex arrangement. Outer ring face to outer ring face, which pushes the two load lines apart and gives the greatest resistance to overturning moment of the three duplex options.C7 – an NSK supplementary code carried on the carton for this lot. It is retained here as a searchable cross-reference only; we do not publish a clearance or preload value against it, because NSK’s own definition for this specific code is not available to us. On a duplex-marked bearing, a guessed preload figure is worse than no figure.

Why the 30 degree angle matters here:
At 105 mm bore the bearing is almost always doing two jobs at once: locating a heavy shaft axially and carrying a radial load. The 30° contact angle steepens the load line through the balls compared with the 15° 7021C, so it takes considerably more one-direction thrust and deflects less under axial load. The price is speed: grease-lubricated limiting speed here is 4,300 rpm. If your spindle needs to spin faster than that, the 15° version, an oil-air system, or a ceramic-ball super-precision bearing is the right route. If it is a boring mill quill, a rotary table, a large gear reducer or a vertical shaft, the 30° angle is doing exactly what you want.

Published ratings and mounting data:
Basic dynamic radial load rating Cr: 80,000 N (8,150 kgf), per ISO 281 at one million revolutions.Basic static radial load rating C0r: 81,500 N (8,350 kgf). Note the static rating slightly exceeds the dynamic rating — normal for a thin-section large-bore ball bearing and a reminder that shock and dwell loads, not fatigue, are often the limit on this kind of part.Limiting speed: 4,300 rpm grease, 5,600 rpm oil — single bearing values, de-rate for preloaded and duplex mountings.Effective load centre a: 51.2 mm from the ring face — use this figure, not the physical bearing spacing, when calculating the span between load lines.Shaft abutment (backing shoulder) diameter da: 115.0 mm. Housing abutment diameter Da: 150.0 mm. Maximum shaft/housing fillet radius ra: 2.0 mm.Ring chamfers: r min 2.0 mm (inner), r1 min 1.00 mm (outer).Mass: approximately 1.840 kg (4.06 lb) per bearing.

Quantity and configuration — read this before ordering:
Each unit is one single bearing. Earlier copy for this item described it as coming in a pack of 2; that was a misreading of the on-hand count. What is true is that there are two pieces in stock, so a buyer who needs a back-to-back pair can take both in one order. The carton designation carries a DB reference, which means the original packaging described a matched pair — but we do not represent the two pieces as a factory-matched, ground-to-preload set. If your rebuild depends on a controlled preload offset, ask us to verify the markings on the actual pieces before you commit; a mismatched back-to-back pair will not produce the preload the spindle was designed around.

Fitting notes:
A single angular contact bearing carries thrust in one direction only and must be axially opposed — a second angular contact bearing, a deep groove bearing, or a shoulder and locknut. Observe the abutment diameters above; a shoulder that reaches past them onto the raceway land will pinch the ring and change the internal geometry. On a thin-section bearing of this diameter, housing roundness and shaft fit matter more than they would on a heavy-section bearing: an out-of-round bore is transmitted almost directly into the raceway. Rings and balls are matched at assembly — do not swap rings between bearings.

Interchange guidance:
Same 105x160x26 mm boundary dimensions, different contact angles: NSK 7021A (30°), NSK 7021C (15°), SKF 7021 CD/P4A and 7021 CDGA/P4A (15°), SKF 7021 ACD (25°), FAG/Schaeffler B7021-C-T-P4S (15°) and B7021-E-T-P4S (25°), NTN 7021, Koyo 7021, NACHI 7021. The 7021ACD designation also carried on this listing is SKF nomenclature, where AC denotes 25°, and 7021E is a dimensional reference used by some suppliers — both are here because buyers search them, not because the angles match. Match the contact angle and the precision class before substituting in either direction.