NSK70BA10XTYDBLP4ABall Screw Support Bearing Set 70x110x18 mm, DB Back-to-Back, Light Preload, P4A Class, Phenolic Cage

Product Description

What this part is

NSK BA-series ball screw support bearings — 70 mm bore, 110 mm outside diameter, 18 mm width per bearing. Phenolic cage, matched and ground for back-to-back mounting at light preload, precision class P4A.

The BA prefix is the important part of this designation. This is not a general-purpose angular contact bearing that happens to fit a screw. NSK’s BA range is a dedicated ball-screw support series, designed around a very different requirement: carrying high axial load with high axial stiffness in a shallow section, rather than balancing radial and axial capacity.

Decoding the designation

70 — bore size in millimetres. Note that NSK numbers this series by actual bore, not by ISO bore code.
BA — ball screw support series.
10X — NSK series and variant code within the BA range.
TY — NSK’s phenolic (synthetic resin) cage designation.
DBL — DB back-to-back, L light preload: a matched pair mounted back-to-back.
P4A — NSK precision class for this series, in the P4 (ABEC 7) band.

What these specs mean in practice

A ball screw’s support bearings determine the positioning stiffness of the whole axis. When the screw is driven, the entire thrust reaction passes through these bearings, and any axial deflection in them appears directly as lost motion at the machine’s tool point — which is why the series is built for axial stiffness above all, and why the preload is not optional. Back-to-back mounting is standard here because it gives the widest effective bearing spread and the best resistance to the moment loads a long screw imposes.

Light preload keeps friction, heat and drive torque down, which matters on a screw that reverses frequently. Heavier preload buys stiffness at the cost of heat, and heat in a ball screw shows up as thermal growth and drifting positional accuracy — so on precision axes the light-preload option is often deliberately chosen even though it is the softer one.

The phenolic cage is a genuine spec that most listings omit: self-lubricating, oil-absorbing and far gentler on the balls than pressed steel during momentary lubrication starvation. It also caps the operating temperature.

Correcting the source data

The listing title carried both DBL (in the primary part number) and DUL. These are not the same thing: DB specifies the mounting as back-to-back, whereas DU specifies that the rings are universally ground so they can be mounted in any arrangement. A DBL set is supplied matched for one specific arrangement. We have published DBL, from the primary part number, and retained the DUL form as a search term only.

Quantity and configuration

The listing title states 2 pieces, consistent with a DBL matched pair, while our stock record shows a quantity of 1 — most likely one pair. Matched pairs in surplus are frequently split, so we are publishing no firm quantity claim and have not altered the inventory record. Contact us before ordering and we will confirm that two matched bearings are physically present. A ball screw support set is not useful as a single bearing.

Published ratings and mounting data

Axial and radial load ratings and limiting speeds are deliberately blank. We could not retrieve NSK’s own published figures for this designation, and BA-series bearings are rated on a different basis from ordinary angular contact bearings — their contact angle is much steeper, so borrowing figures from a 70-envelope 7000-series bearing would be badly wrong. We have therefore also not published a contact angle. Contact NSK or an authorised distributor with the full designation if a certified figure is required.

Fitting notes

Observe the ring match marks and thrust markings; a back-to-back pair mounted face-to-face has entirely different stiffness and moment behaviour. Never shim, lap or regrind the ground faces — the preload lives in them. Clamp both rings fully against their shoulders; a partially clamped pair carries no preload, and on a ball screw that means lost motion. Press only on the ring being fitted, never through the balls.

Interchange guidance

Match within the BA series and on bore size, preload grade and precision class. Do not substitute an ordinary 7014-envelope angular contact bearing because the bore and outside diameter happen to be close — the internal geometry and contact angle are different and the axial stiffness will not match. Comparable dedicated ball-screw support bearings exist from other makers, including FAG’s 7602-series 60° designs, but they must be matched on angle and stiffness rather than envelope alone.