SKF71906CDP4ADGASuper-Precision Angular Contact Ball Bearing 30 x 47 x 9 mm, 15 Degree Contact Angle, P4A, Universally Matchable Light Preload, Open, 1 Pc

Product Description

What this part is

A single SKF super-precision angular contact ball bearing in the 71906 envelope — 30 mm bore, 47 mm outside diameter, 9 mm width. Open, 15° contact angle, P4A tolerance class, and universally matchable so that two of them clamped together produce light preload. This is a 719-series extra-light-section bearing, made for high-speed machine-tool spindles, grinding heads, precision rotary tables and any position where the housing envelope is tight and running accuracy is critical.

Decoding the designation

71906 — SKF 719 series, the extra-light section super-precision angular contact family. Size 30 x 47 x 9 mm, sharing bore and outside diameter with a 7906 but in the thinner section.
CD — 15° contact angle in SKF’s super-precision scheme. SKF uses ACD for the 25° build, so the single letter difference changes the bearing.
P4A — SKF super-precision tolerance class, tighter than P5 on bore, outside diameter and running accuracy.
DGA — universally matchable for light preload. GA is light, GB moderate, GC heavy.

Correcting the source data

Earlier copy on this listing gave the width as 12 mm and described the bearing as supporting axial load in both directions. A 71906 is 30 x 47 x 9 mm, and a single-row angular contact bearing takes thrust in one direction only. Both are corrected here — the 9 mm width in particular matters when you are working out a spacer stack.

What these specs mean in practice

The 719 series is the thin one. At 9 mm across a 30 mm bore, this bearing gets a spindle into a housing that a standard 70-series bearing would not fit, and it does so without giving up running accuracy — which is the trade a designer makes when space beats load capacity. The 15° contact angle points in the same direction: it keeps ball loading closer to radial, so centrifugal loading and heat generation stay low and the bearing turns fast and cool. It carries appreciably less thrust than the 25° ACD build of the same size and offers less axial stiffness. Light preload is the third element of the same choice, favouring low running temperature and high speed over rigidity. Universal matchability is the practical convenience: any two DGA bearings of this designation can be clamped together in any orientation and the ground stand-off produces light preload with no shimming. P4A running accuracy only reaches the shaft if the seats are ground and true to match — on a 9 mm wide ring, a distorted housing bore will show up immediately.

Quantity and configuration

1 Pc — one bearing. Universally matchable, so if the spindle uses a preloaded set, order two carrying this same DGA designation and clamp them together for light preload.

Fitting notes

Thrust is carried in one direction only, so the assembly must oppose it — a second bearing, a spring pack or a shoulder. Orientation matters: the wide land of the outer ring faces the thrust. A thin-section ring is easy to distort, so press only on the ring being fitted, never through the ball complement, and never drift a 719-series bearing home with a hammer. Interference fit adds preload on top of what is ground in, so check shaft and housing sizes against the spindle drawing first. Lubricate sparingly with a spindle grease or run oil-air; over-greasing a 15° bearing at speed is a reliable way to overheat it.

Interchange guidance

Genuine 15° cross-references in this envelope include FAG B71906-C-T-P4S, NSK 71906C, NTN 71906C and Fafnir/Timken 2MM9306WI CR — all 30 x 47 x 9 mm at 15°, and all real interchanges. SNFA is also worth searching, since SNFA was absorbed into SKF and its numbers still circulate. Related sizes fill the identical envelope at a different contact angle: 71906 ACD is the 25° build. That is a different part with higher thrust capacity and lower speed capability, not a substitute, though worth knowing about if your drawing calls for 25°. Preload grade likewise is not interchangeable — DGB (moderate) and DGC (heavy) exist in this size and change spindle stiffness and running temperature. Do not confuse the 719 series with the 79 or 70 series at the same bore: 7906 and 7006 share the 30 mm bore but are wider and stiffer, and will not drop into a 9 mm housing.