NSKSuper 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 data

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.

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.