NTN7917CP5Precision Angular Contact Ball Bearing 85x120x18 mm, 15° Contact Angle, ISO P5 / ABEC 5, Thin Section, Open

Product Description

What this part is

An NTN 7917C precision angular contact ball bearing, 85 mm bore x 120 mm outside diameter x 18 mm wide — the 71917 / 7917 thin-section spindle envelope. It carries radial load plus thrust in one direction, and the high shoulder must face the thrust.

Decoding the designation

7917 – single-row angular contact ball bearing, 19-series thin section, 85 x 120 x 18 mm. The 71917 form describes the same bearing.
C – contact angle 15° in NTN nomenclature.
P5 – ISO tolerance class 5, equivalent to ABEC 5.

What these specs mean in practice

15° is the high-speed end of the contact-angle range. The shallow angle keeps the ball load path closer to radial, so centrifugal ball loading and heat generation stay low and the bearing tolerates a higher DN value than a 25° or 40° equivalent — at the cost of thrust capacity and axial stiffness. That is the right trade for a fast, lightly-thrust-loaded spindle and the wrong one for a heavy boring position.

An 18 mm width on an 85 mm bore makes this a thin-section bearing, specified where axial space in the spindle nose is tight and several bearings have to be stacked in a short length. P5 / ABEC 5 tightens bore, outside diameter, width and running accuracy well beyond a standard bearing without going to the cost of P4. It is the grade used for precision drive spindles, indexing tables and rotary axes where repeatable location matters but the machine is not running at super-precision speeds — if your drawing calls for P4 or ABEC 7, this bearing is a class short even though the envelope is identical.

Published dimensions

Bore (d): 85 mm
Outside diameter (D): 120 mm
Width (B): 18 mm
Contact angle: 15°
Rows: 1
Precision: ISO P5 / ABEC 5
Closure: open, no seals or shields

Quantity and configuration

Sold as one bearing — a complete unit with inner ring, outer ring, ball complement and cage. This is a plain single with no universal-grinding or preload suffix, so it is not a matched set and will not develop a defined preload if two are simply clamped together. Where a spindle drawing calls for a matched pair, order an NTN GD2 universally ground designation instead.

Fitting notes

Orient the high shoulder towards the thrust load — fitted backwards the balls climb the raceway shoulder and the bearing fails quickly. Press or induction-heat onto the shaft against the inner ring only, and press into the housing against the outer ring only; never route mounting force through the balls. A single angular contact bearing locates the shaft in one direction only, so it needs an opposing bearing somewhere in the arrangement. The bearing is open, so it depends entirely on the housing for sealing.

Interchange guidance

Direct 85 x 120 x 18 mm precision 15° equivalents: NSK 7917CTYNP5 and 71917CTYNP5 (NSK C = 15°), SKF 71917 CD/P4A (SKF CD = 15°, one class tighter), FAG B71917-C-T-P4S (FAG C = 15°, one class tighter), Fafnir/Timken 2MM9117WICR (2MM = 15°), RHP 7917CTP5 (RHP C = 15°). Carried as dimensionally-correct cross-references with the difference named: NSK 7917A5TYNP5 and SKF 71917 ACD/P4A are the same envelope at 25°, and Fafnir 3MM9117WI is 25° — same bore and housing, more thrust capacity, less speed. Note the class as well as the angle: several of the equivalents above are P4 / ABEC 7 rather than P5, which is a tighter grade and a valid upgrade but not a like-for-like match on tolerance.