NSK7908A5TYDULSuper Precision Angular Contact Ball Bearing 40x62x12 mm, 25 Degree Contact Angle, Single Universally Ground Light Preload, Thin Section

Product Description

What this part is

NSK 7908A5TYSUL, a super-precision angular contact ball bearing in the 19-dimension thin-section series, 40 mm bore by 62 mm outside diameter by 12 mm width, with a 25° contact angle, universally ground at light preload. Brand: NSK. Bearing Type: Super-precision angular contact ball bearing. Bore: 40 mm. Outside Diameter: 62 mm. Overall Width: 12 mm. Contact Angle: 25°. Preload: Light. Arrangement: SUL, single universally ground. Number Of Rows: Single row. Rolling Elements: Steel balls. Bearing Material: Bearing steel. Closure Type: Open. Series: 79, ISO 19 dimension series. Base Number: 7908A5. Design Units: Metric. Harmonization Code: 8482.10.50.68. The 19-series is the thin-section range, a slim ring cross-section for a given bore, for positions where radial space is tight and speed matters more than load capacity.

Published ratings and mounting dimensions

Dynamic Load Rating: 14.3 kN. Static Load Rating: 11.2 kN. Limiting Speed: 14,000 rpm on grease, 18,000 rpm on oil. Item Weight: 0.110 kg. Contact Point Distance a: 17.9 mm. Chamfer r minimum: 0.6 mm. Chamfer r1 minimum: 0.30 mm. Shaft Fillet Diameter da: 45.0 mm. Housing Shoulder Diameter Da: 57.0 mm. Housing Fillet ra: 0.6 mm. Operating Temperature Range: -30 °C to 120 °C.

Quantity and configuration

Unit Quantity: 1 Pc. SU means single universally ground, so this is one bearing. The faces are ground so that any number of these bearings stack back-to-back, face-to-face or in tandem and the specified light preload results from clamping them together, with no shims and no measurement. Two SUL bearings mounted back-to-back give the same result as a DUL pair. That is why universally ground singles are the practical way to build and repair spindle stacks.

Decoding the designation

7908: 19-dimension series angular contact ball bearing, 40 x 62 x 12 mm, in NSK’s designation style. A5: Contact Angle 25° in NSK’s scheme, where C is 15°, A5 is 25°, A is 30° and B is 40°. SUL: single universally ground, light preload; the preload range runs SUEL extra-light, SUL light, SUM medium, SUH heavy. Searchable variants: 7908A5TYSUL, 7908-A5-TY-SUL, 7908 A5 TY SUL, 7908A5TYNSUL, 7908A5SUL, 7908A5, 71908.

What 25° and light preload buy

25° is the middle spindle angle. It carries markedly more thrust and gives more axial stiffness than a 15° bearing, without the speed and heat penalty of a 30° or 40° bearing. Light preload keeps heat generation and friction low and preserves speed capability, at the cost of stiffness. The combination suits high-speed spindle positions that still see real cutting thrust.

Contact angle is consistent across a spindle stack. A 25° bearing stacked against a 15° bearing takes a disproportionate share of the thrust while the shallower bearing runs underloaded and skids, a failure that looks like a lubrication problem and is a specification problem.

Fitting notes

A single angular contact bearing carries thrust in one direction, and thrust direction is observed on installation. When stacking universally ground bearings, the etched face marks align according to the intended arrangement. Bearings ship preserved rather than charged with service lubricant.

Interchange guidance

71908 is the ISO and European designation for the same 40 x 62 x 12 mm envelope and 7908 is the NSK and JIS style for it; both are correct. Angle-equivalent designations at 25°: 71908ACD in SKF format, where AC denotes 25°; B71908E in Schaeffler format, where E denotes 25°; the 3MM9308WI family in Fafnir and Timken format. Suffix letters mean different angles in different makers’ schemes, so the scheme is stated with the number.