NSK7004CTYNDBLP4Super Precision Angular Contact Ball Bearing Matched Set 20x42x12 mm, 15 Degree Contact Angle, ABEC 7, Back-to-Back Duplex, Light Preload, Polyamide Cage, 2 Pieces

Product Description

What this part is

A matched pair of super precision angular contact ball bearings in the ISO 70 light series, 20 mm bore, 42 mm outside diameter, 12 mm width per bearing, ground as a back-to-back duplex set with light preload built in.

Decoding the designation

7004 — ISO 70 series angular contact ball bearing, 20 x 42 x 12 mm.
C — NSK contact angle code for 15°. In NSK’s scheme A is 30° and A5 is 25°, so a 7004C and a 7004A5 are different bearings.
TYN — moulded polyamide cage.
DB — duplex mounted back-to-back.
L — light preload.
P4 — ABEC 7 tolerance class.

What these specs mean in practice

A 15° contact angle is the high speed end of the super precision range: it gives the highest limiting speed and the least heat, at the cost of thrust capacity compared with a 25° or 30° bearing. Back-to-back mounting puts the two contact lines diverging outward, which produces a wide effective bearing span and therefore good resistance to overturning moments — the reason DB is the default for spindle nose positions. Light preload keeps friction and thermal growth low, which is what you want on a small, fast spindle; heavy preload on a 20 mm bore at speed simply cooks the lubricant. The polyamide cage is quiet and self lubricating but sets a temperature ceiling around 120 °C, so it is not the choice for a hot running or steam cleaned application.

Quantity and configuration

Two pieces, ground as a set. Matched sets must stay together — substituting one bearing from another set destroys the preload the DBL designation describes, because preload here comes from ground ring offsets rather than from a spacer.

Fitting notes

Mount with the marked ring faces together in the orientation the etching indicates. Clamp both inner rings and both outer rings solidly; a loose clamp on either ring means the ground offset never closes and the set runs with clearance instead of preload. Do not mix with a 7004A or 7004A5 — different contact angle, uneven load sharing, early failure.

Published ratings and mounting data

Dynamic and static load ratings and the limiting speed for this specific set designation are not published by NSK in a source we could verify, and set ratings are not simply twice the single bearing figures, so they are left blank rather than estimated.

Interchange guidance

The KL3-01 marking carried in the title is a carton or customer legend rather than an NSK catalogue suffix; it is retained as a search term. Same envelope 15° super precision alternatives are found as B7004C-T-P4S (FAG), 7004CD/P4A (SKF) and 2MM9104WI (Fafnir/Timken). Confirm preload class and mounting arrangement before substituting.