Timken71906E-T-P4-SULSuper Precision Angular Contact Ball Bearing 30x47x9 mm, 25° Contact Angle, P4S, Phenolic Cage, Universally Matchable Light Preload

Product Description

What this part is

This is a super precision single-row angular contact ball bearing in the extra-light 719 dimension series: 30 mm bore, 47 mm outside diameter, 9 mm width. It is a spindle bearing — the class of bearing used in machine tool spindles, grinding heads, high-speed rotary tables and precision gear trains, where the requirement is not brute load capacity but running accuracy, axial stiffness and controlled preload. It has a 25° contact angle, ISO P4S accuracy, a phenolic (fabric-laminate) cage that rides on the outer ring land, steel balls, and is ground as a single universally matchable bearing set for light preload. Quantity available is 2, which means a matched pair can be bought together.

Correcting the source data

This record carries two different manufacturers’ numbering schemes at once, and it is worth saying so plainly rather than letting a buyer discover it after the box is open. The designation 71906E-T-P4-SUL is FAG/Schaeffler syntax, not Timken syntax, and it is also slightly mis-transcribed — the correct FAG part number is B71906-E-T-P4S-UL (leading B for steel balls, P4S rather than P4, and SUL rendered as -UL following the accuracy code). The Timken equivalent for the same bearing is the Fafnir WI number 3MV9306WICRSUL, which is also already in this listing. Both designations describe the same physical bearing: 30 mm bore, 25° contact angle, phenolic cage, single universally matchable, light preload. Because both schemes appear here, we recommend confirming from the product photographs which brand’s marking is physically on the ring in the box before ordering, particularly if your maintenance system requires a specific brand of record.

Decoding the FAG designation B71906-E-T-P4S-UL

B — steel balls. The hybrid ceramic-ball versions of this family carry HC or HCB instead. If you specifically need ceramic balls for a high-speed or electrically-noisy spindle, this is not that bearing.719 — extra-light dimension series. Thin section, small ball complement, chosen when the spindle diameter is fixed and radial envelope is tight.06 — 30 mm bore.E — 25° contact angle.T — phenolic / fabric-laminate cage. This is the specification most often misread, so to be explicit: T does not mean a machined metal cage on this family. It means a resin-impregnated fabric laminate cage.P4S — ISO P4S accuracy, which is P4 running accuracy combined with P2-level axial runout. It is a specific composite class, not a typo for plain P4, and it is tighter than P4 in the axial direction.U — single bearing, universally matchable.L — light preload.

Decoding the Timken / Fafnir WI number 3MV9306WICRSUL

3 — ABEC-7 / ISO P4 accuracy class.MV — 25° contact angle, super precision. In the Fafnir WI system MM denotes 15° and MV denotes 25°. This two-letter code is the single most important character pair on the ring, and confusing MM with MV is the most common way people order the wrong angle.9306 — 719 dimension series, 30 mm bore.WI — spindle bearing construction.CR — outer-ring-land-riding phenolic cage.SUL — single bearing, universally matchable, light preload.

Published ratings and speed data

Bore d: 30 mm — Outside diameter D: 47 mm — Width B: 9 mmDynamic radial load rating Cr: 8.1 kNStatic radial load rating C0r: 4.15 kNFatigue limit load Cu: 0.425 kNReference speed: 43,000 rpmLimiting speed: 28,000 rpmWeight: 0.050 kgFAG UPC: 4012801167697
Two things are not published and we are not going to estimate them. First, the actual preload force in newtons that the L (light) preload class produces on this size — FAG does not publish a figure in the open data for this bearing, and preload force scales with size and arrangement, so borrowing a number from a neighbouring size would be misleading. Second, the abutment and fillet dimensions (shaft and housing shoulder diameters and maximum fillet radii). If you need either for a design calculation, request them from Schaeffler or Timken engineering for the specific designation.

Reference speed versus limiting speed — why the two numbers differ:
Reference speed (43,000 rpm) is a thermally-derived figure calculated under standardised reference conditions and is used for comparison and for thermal speed-rating calculations. Limiting speed (28,000 rpm) is the mechanical ceiling above which the cage, lubrication method and internal geometry are no longer considered safe in normal service. For practical design work, treat 28,000 rpm as your ceiling, not 43,000. And note that the achievable speed in a real spindle is usually set by lubrication and preload before it is set by either catalog number — a grease-packed light-preload pair will not reach the same speed as an oil-air lubricated one.

What a 25° contact angle trades away versus 15°:
The contact angle is the design decision that most affects how this bearing behaves, and there is a genuine trade-off rather than a better and worse option. A larger angle (25°, the E / MV code) directs a greater share of the load along the axial path: you get more axial stiffness and more thrust capacity. That is what you want on a milling spindle, a boring head, a screw-drive support or anywhere the cutting force has a large axial component and deflection under thrust is what limits accuracy. The cost is lower speed capability and more heat generation at high rpm, because the larger angle increases ball spin and gyroscopic moment. A 15° angle (the C / MM code) inverts the trade: lower stiffness, less thrust capacity, but higher speed capability and less heat — the high-speed grinding and high-rpm router choice. In short: 15° is the high-speed choice, 25° is the stiff choice. Do not substitute one for the other in a matched spindle stack; the spindle was designed around one angle, and swapping angles changes both the stiffness curve and the thermal behaviour of the whole assembly.

What SU (single, universally matchable) means and why it matters:
This is the feature that makes the bearing genuinely convenient, and it is widely misunderstood. A universally-ground single bearing has its ring faces ground so that any two bearings of the same designation can be assembled together in any orientation — back-to-back (DB), face-to-face (DF), or in tandem (DT) — and will automatically produce the correct light preload with no shims, no grinding and no measuring. That is the whole point of the U code. It means you are not locked into buying a factory-matched pair as a single non-divisible item, and you are not stuck sourcing spacers. You can also use a single unit on its own where the design calls for one bearing, or build a triplet or quad stack from three or four units. Compare this with a factory-matched DUL pair, which is supplied as an inseparable set and cannot be split. Universally matchable singles give you the flexibility of stocking one part number and configuring the arrangement at the bench.

Quantity and configuration

Two units are in stock. Because these are universally matchable singles, the two can be purchased together as a matched light-preload pair and mounted back-to-back, face-to-face or in tandem, producing the same result as an off-the-shelf DUL pair. If you need a pair, take both. If you need only one, a single unit is perfectly usable on its own or as a replacement for one member of an existing stack of the same designation. Do not mix these with a bearing of a different contact angle or a different preload class in the same stack.

Interchange guidance and the parts frequently confused with this one:
B71906-E-T-P4S-UL (FAG / Schaeffler) — 25°. Clean 1:1 equivalent; this is the same bearing under FAG’s scheme.3MV9306WICRSUL (Timken / Fafnir) — 25°. Clean 1:1 equivalent; this is the same bearing under Timken’s WI scheme.3MM9306WI DUL (Timken / Fafnir) — NOT an equivalent. Frequently confused with this part because the numbers look almost identical, but MM means 15°, not 25°, and DUL means a duplex matched pair, not a single. It is a different contact angle and a different sales unit. If you were quoted 3MM9306WI DUL against this listing, someone has mismatched the part.71906A5 / 71906A5TRSU (NSK) — NSK’s A5 code denotes 25° (their C code denotes 15°), so this should be the equivalent angle. Marked unconfirmed — we could not verify it on an NSK published page, so verify with NSK before substituting.71906ACD/P4A (SKF) — SKF’s AC denotes 25° and CD denotes a machined cage, so the angle should match. Note the bare designation “71906ACD” carries no preload suffix; SKF’s light preload code is GA, so a bare 71906ACD is not specified for light preload. Marked unconfirmed.
The pattern to take away: on angular contact spindle bearings, every manufacturer encodes contact angle and preload differently, and a designation that matches on bore and series can still be the wrong bearing. Match the angle and the preload class explicitly, not just the dimensions.