NSK7017ADBC7P6Angular Contact Ball Bearing 85x130x22 mm 30° ABEC 3 Back-to-Back Ground Half Pair

Product Description

What this part is

One single-row angular contact ball bearing, 85 mm bore, 130 mm outside diameter, 22 mm width, carrying a 30° contact angle. It is ground for a back-to-back light-preload pair and is supplied as one half of that pair.

Decoding the designation

The 70 prefix and bore code 17 give ISO dimension series 70 at an 85 mm bore. In the NSK scheme A is a 30° contact angle — distinct from A5 at 25° and C at 15°. DB is a back-to-back matched arrangement and P6 is ISO class 6, which corresponds to ABEC 3. The suffix -1/2PR is the half-pair marking: one bearing, not two. The alternate carton form 7017A DBL P6 adds L for the light preload grade.

What these specs mean in practice

A 30° contact angle is the most thrust-biased of the common angular contact angles. Axial capacity and axial stiffness rise steeply with contact angle, so a 30° bearing carries substantially more thrust than a 15° or 25° bearing of the same envelope. The trade is speed and radial capacity: the steep load line increases ball centrifugal and gyroscopic effects, so the limiting speed falls and heat generation rises at equal duty. A 30° bearing belongs where thrust dominates.

Back-to-back grinding is what turns two bearings into a stiff unit. In a DB stack the load lines diverge outward, giving the pair a wide effective bearing span and therefore real moment stiffness — the property that resists shaft tilting rather than just radial or axial displacement. Face-to-face grinding does the opposite, converging the load lines and tolerating misalignment instead.

P6 is ISO class 6, equivalent to ABEC 3. It is a precision class above normal but well below the P4 and P5 super-precision grades used on ground machine tool spindles, which places this bearing in general precision machinery rather than in a finish-critical spindle stack.

Quantity and configuration

1 Pc. The -1/2PR suffix denotes a single bearing, half of a back-to-back matched pair. The matching second half is a 7017A of the same DB grind and preload grade.

Thrust direction

A single-row angular contact ball bearing carries thrust in one direction only. A completed back-to-back pair takes thrust in both directions, one row per direction, but this piece on its own does not.

Fitting notes

The bearing mounts with its thrust face toward the load, following the face marking. In a back-to-back arrangement the two outer rings meet at their narrow lands and the inner rings are clamped solid so the ground relief sets the preload without shimming. Locknut load is drawn against the inner ring face so it passes through the rings and never through the ball complement.

Interchange guidance

The base number is 7017, and the 30° angle is what narrows it. Same-envelope bearings differing in contact angle, arrangement, preload grade or tolerance class — 7017C at 15°, 7017A5 at 25°, face-to-face DF and tandem DT sets, and P4 or P5 class pieces — are related sizes rather than interchanges. A bearing not ground for a DB pair will not develop the specified preload when clamped against this one.