FAGSuper Precision Angular Contact Spindle Bearing 55 x 80 x 13 mm 15° Contact Angle P4

Product Description

What this part is

A single-row super-precision angular contact spindle ball bearing, 55 mm bore, 80 mm outside diameter, 13 mm width, from the 719 ultra-light dimension series. The narrow section and small ball complement of the 719 series give a high speed capability and a slim cross-section, which is why the series is standard on machine-tool spindles where the shaft diameter is set by stiffness rather than by load.

Decoding the designation

719 — single-row angular contact ball bearing, ISO dimension series 19 (ultra-light section).
11 — bore code, 11 × 5 = 55 mm bore.
C — 15° contact angle in the FAG scheme.
TG — FAG cage execution for this series.
P4 — ABEC 7 / ISO class 4 super-precision tolerances.
B prefix on the alternate form — FAG’s 15° spindle bearing line; UL denotes a universally ground piece and P4S the tightened running-accuracy grade.

What these specs mean in practice

A 15° contact angle is the high-speed choice. The load line sits close to the radial plane, so ball centrifugal force and the gyroscopic moment stay modest as speed climbs, and the bearing generates less heat than a steeper-angle bearing at the same rotational speed. The trade is axial capacity and axial stiffness, both of which rise with contact angle: a 25° bearing of the same envelope holds a spindle’s face position harder under thrust and runs slower doing it.

The 719 series compounds the speed bias. A thin cross-section carries smaller balls on a pitch diameter close to the bore, which keeps the ball surface speed and the cage load down at high rpm and keeps radial capacity modest, so the series is chosen where rpm and shaft stiffness dominate and the load is light to moderate.

P4 accuracy holds bore, outside diameter, width and ring runout to single-digit micron limits, which is what keeps the ball path concentric with the spindle axis and the tool tip on centre. The published figures for this envelope in the 15° super-precision execution are a dynamic rating of 23.5 kN and a static rating of 14.4 kN, with a reference speed of 26,000 rpm and a limiting speed of 17,000 rpm.

Published ratings and mounting data

Bore: 55 mm (2.1654 in)
Outside diameter: 80 mm (3.1496 in)
Width: 13 mm (0.5118 in)
Rows: 1
Contact angle: 15°
Dynamic load rating C: 23.5 kN
Static load rating C0: 14.4 kN
Reference speed: 26,000 rpm
Limiting speed: 17,000 rpm
Accuracy: P4 (ABEC 7 / ISO class 4)
Closure: open, both faces

Quantity and configuration

Single bearing. 1 Pc.

Fitting notes

The bearing is directional: the wide outer-ring land is the back face and carries the thrust, and a back-to-back pair is assembled with those lands outward. Seats are ground and measured to super-precision practice, typically j4 to k4 on a rotating shaft and H5 to J5 in the housing, and the rings are clamped through spacers so the axial force passes through the ring faces rather than through the ball path. Assembly is done clean, since a few microns of debris under a clamped face reads directly as spindle runout.

Cross-reference guidance

71911-C and B71911-C are FAG’s designations for the 15° bearing in this envelope, and 71911C is the ISO base number shared with other makers of a 15° angular contact bearing at 55 x 80 x 13 mm. Bearings in this envelope with a different contact angle, accuracy class or sealing — the 25° E execution, the sealed 2RSD variants, and hybrid HCS or XCS ceramic-ball executions — are not the same part. The 71910 at 50 x 72 x 12 mm is a different size in the same series.