NSK7005ATYDBC7P5High Precision Angular Contact Ball Bearing Matched Back-to-Back Pair (2 Pcs), 25 x 47 x 12 mm, 30 Degree Contact Angle, ABEC-5 P5, Polyamide Cage

Product Description

What this part is

A matched back-to-back pair of NSK high-precision angular contact ball bearings, 25 mm bore, 47 mm outside diameter, 12 mm wide each. Both carry a 30° contact angle, are ground to ISO Class 5 (ABEC 5) and run a ball-guided polyamide resin cage. Read that combination as a thrust-and-position job: ball screw ends, precision gearbox and pump shafts, spindle and rotary-table assemblies where axial location matters as much as radial support.

Decoding the designation

Decoded against NSK’s own numbering system for high-precision angular contact ball bearings. Suffixes are brand-specific and this decode does not transfer to SKF, FAG or Timken numbers.

7005 — single-row angular contact ball bearing, 70 (10) dimension series, bore number 05 = 25 mm bore. 47 mm outside diameter, 12 mm width.
A — 30° contact angle. NSK’s scheme runs C = 15°, A5 = 25°, A = 30°. Do not read this against SKF, where AC = 25°; the letter A on an NSK number is the widest of the three angles, not the middle one.
TY — ball-guided polyamide resin cage. NSK’s current catalogue writes this cage as TYN and rates it to dmn 1,400,000 with a 120°C operating limit; TY is the form printed on this carton.
DB — back-to-back duplex arrangement, the O configuration. The opposite hands are DF face-to-face and DT tandem.
C7 — a preload call-out. NSK/RHP designation code lists give C7 as light preload; NSK’s current super-precision catalogue uses EL / L / M / H for preload and CA / CP for special clearance and special preload, and does not print a C7 row. We are quoting the code list rather than a live catalogue page, so treat the exact preload value as unconfirmed — ask before ordering if your spindle depends on a specific figure.
P5 — ISO tolerance class 5, equivalent to ABEC 5.

The carton also carries UB-13, an NSK internal code we have not found a published decode for. It is left undecoded rather than guessed. Ring markings read 7005, NSK, JAPAN.

Why back-to-back, and what it costs you

Mounted back-to-back, the two contact-angle lines diverge outward, so the effective load centres sit further apart than the bearing width. That is what gives a DB pair its resistance to moment (tilting) loads and its ability to take thrust in either direction from one bearing station. Face-to-face has the load lines converging and is more forgiving of shaft-and-housing misalignment but much weaker in moment. Tandem stacks both angles the same way to double one-direction thrust and takes nothing in reverse.

The 30° angle is the high-thrust end of NSK’s standard precision range. Compared with a 15° bearing it carries substantially more axial load and is axially stiffer, and it gives up speed ceiling and radial rigidity to get there. If your spindle is chasing rpm rather than thrust, a 15° C-suffix bearing is the correct part.

The polyamide cage is light and quiet and tolerates momentary lubrication starvation better than steel, but 120°C is the wall. Polyamide also does not like long exposure to certain synthetic oils and EP additives — if the spindle runs hot or on aggressive oil, a phenolic (TR) or machined cage version is the safer specification.

Published ratings and mounting data

Bore (d): 25 mm
Outside diameter (D): 47 mm
Width (B): 12 mm per bearing — 24 mm for the pair mounted
Contact angle: 30°
Basic dynamic load rating (Cr): 13,500 N per bearing
Basic static load rating (C0r): 6,850 N per bearing
Permissible axial load (Pa): 4.55 kN
Limiting speed: 20,900 rpm grease-lubricated, 27,800 rpm oil or oil-air
Effective load centre (a): 16.4 mm
Shaft abutment diameter (da min.): 30 mm
Housing abutment diameter (Da max.): 42 mm; Db max. 44.5 mm
Fillet radii: r min. 0.6 mm, r1 min. 0.3 mm; ra max. 0.6 mm, rb max. 0.3 mm
Recommended grease quantity: 0.48 g per bearing
Tolerance class: P5 (ISO Class 5 / ABEC 5)
Cage: polyamide resin, ball guided
Closure: open — no seals, no shields
Rows: one per bearing
Mass: approx. 0.079 kg per bearing, approx. 0.158 kg for the pair

For reference, NSK’s published preload steps for this bearing size are EL 25 N (63 N/µm axial rigidity), L 135 N (112), M 299 N (149) and H 507 N (183). Limiting speeds are catalogue figures for the bearing alone; a preloaded DB pair in a real housing will run lower.

Quantity and configuration

This listing supplies two bearings — one matched DB set, in the original NSK carton with the factory handling slip, sealed in the NSK poly bag. That is worth stating plainly, because DB describes how two bearings behave together, not what is in the box: duplex sets get split all the time, leaving a carton that still says DB with a single bearing inside. This one has not been split. The photographs show both bearings still bagged together.

Because the pair is ground as a set, no shims, ground spacers or preload adjustment are needed — clamp the rings up solid and the designed preload is what you get. Do not mix one of these against a bearing from a different box; the matching is the product.

Fitting notes

Angular contact bearings are directional and a DB pair only works one way round. Each outer ring has a thick land on one face and a thin land on the other; the two thin (marked) faces must go outward for back-to-back. Assemble it inside out and you have built a face-to-face pair with the wrong preload and no moment stiffness.

An ABEC-5 bearing delivers ABEC-5 running accuracy only if the shaft and housing earn it. Check the journal and bore for wear and size before fitting, mount clean, press evenly on the ring being fitted, and never let mounting force pass through the balls. Fill grease to the recommended quantity rather than packing the cavity — overfilling a 20,000 rpm-class bearing is a heat problem, not insurance.

Interchange guidance

Same-envelope 25 x 47 x 12 mm 30° precision equivalents include SKF 7005 ACD/P4ADGA and 7005 ACDGA/P4A (note the SKF angle is 25°, so it is an envelope match, not an angle match), FAG B7005-E-T-P4S-DB and 7005-B-XL-TVP for the standard-tolerance version, NTN 7005ADB and Nachi 7005ADB. NSK’s own related numbers are 7005AW (pressed-steel cage, standard tolerance), 7005A5 (25°) and 7005C (15°) — those last two are different contact angles and are not drop-in equivalents.

Match contact angle, tolerance class, arrangement and preload before you swap, in that order. RHP precision bearings were absorbed into NSK, so an RHP number in an older machine manual may legitimately land here.