NSK40TAC90BSUC10PN7BBall Screw Support Bearing 40x90x20mm 60 Degree Thrust Angular Contact Single Universally Ground

Product Description

What this part is

An NSK 40TAC90B ball screw support bearing: a 60° thrust angular contact ball bearing, 40 mm bore x 90 mm OD x 20 mm wide, universally ground so it can be run alone or stacked into a matched set. These sit at the fixed end of a machine tool ball screw, where the whole feed force of the axis passes through the bearing as pure thrust.

Decoding the designation

40 — 40 mm boreTAC — NSK thrust angular contact ball screw support series, 60° contact angle90 — 90 mm outside diameterB — series design variantSU — single, universally groundC10 — NSK preload class codePN7B — NSK precision class for ball screw support bearings

Why this is not an ordinary angular contact bearing:
Ball screw support bearings are a distinct family and they are mis-specified constantly. A 60° contact angle is far steeper than the 15°, 25° or 30° of a spindle bearing, which trades away radial capacity and speed to obtain very high axial load capacity and, more importantly, very high axial stiffness — that stiffness is what keeps a CNC axis positioning accurately under cutting load. Fitting a 15° or 25° angular contact bearing of the same envelope into a ball screw end will feel like it fits and will destroy the axis stiffness. Equivalents from other makers in this family are FAG 7602 series, NTN BST, Timken MM…BS and RHP BSB — not their ordinary 7000-series numbers.

Published specifications

Bore: 40 mmOutside diameter: 90 mmWidth: 20 mmContact angle: 60°Bearing type: thrust angular contact ball, ball screw supportDynamic load rating: 56 kNStatic load rating: 99.5 kNPrecision class: NSK PN7BPreload class: C10Ring grinding: universal (SU)Maximum operating temperature: 120 °CRows: 1Closure: open
The static rating being higher than the dynamic rating is normal for this family — it reflects the very large axial contact area a 60° angle produces.

Quantity and configuration

One bearing. Universally ground rings mean it can be combined with identical bearings back-to-back, face-to-face or in tandem to build the DB, DBB, DBD or tandem stacks that ball screw fixed ends commonly use. A single bearing takes thrust in one direction only, so a screw that must be located both ways needs at least two.

Fitting notes

Match the full designation when building a stack, including the preload class — mixing preload classes in one stack gives an unpredictable result. The bearing is direction-sensitive: identify the thrust face before assembly. Clamp the stack as a unit and tighten the screw-end lock nut to the machine builder’s figure; a loose lock nut is the most common cause of lost axis stiffness and backlash complaints that get blamed on the screw. Mount clean, press only on the ring being fitted, and keep the grease charge modest.

Interchange guidance

Search terms include 40TAC90BSUC10PN7B, 40TAC90B SUC10PN7B, 40TAC90-B-SUC-8-PN-7B and 40TAC90B. Note that the source carton also shows a SUC-8 form; the C8 and C10 codes are different preload classes, so match the code stamped on the bearing you are replacing. Related but NOT interchangeable: ordinary 7208-envelope angular contact bearings at 15° or 25°, and DU (duplex-ground) versions of this number. Genuine cross-family equivalents are FAG 7602040-TVP, NTN 40TAB09 / BST40 and RHP BSB040090 class parts — all 60° ball screw support types.