NSK 70BNR10H NSKROBUST Super Precision Angular Contact Bearing

An ultra-high-speed angular contact bearing with ceramic balls for machine tool spindles

The NSK 70BNR10H is a super precision angular contact ball bearing from the NSKROBUST ultra-high-speed range. It has a 70 mm bore, 110 mm outside diameter and 20 mm width, an 18 degree contact angle and ceramic (silicon nitride) balls running in bearing steel rings, which the H in the designation indicates. The ceramic balls are lighter than steel balls, which lowers centrifugal load and heat at speed and allows the grease limit of 20,000 rpm and oil limit of 31,200 rpm listed for this size. The range is aimed at machine tool main spindles, high-speed motor spindles and other applications where precision, stiffness and speed matter together. It is a specialist item rather than a general-purpose bearing.

Technical specifications

Size table for NSK BNR10H bearings

Rows come from the NSK super precision angular contact bearing tables for the BNR10 series with H-type material. Load ratings are in kN as printed.

Reading the designation and ordering

The NSK numbering system for the NSKROBUST series runs from nominal bore diameter and bearing type through dimension series and material to cage, lubrication holes, seal, arrangement, preload, accuracy and grease. Material codes include S (bearing steel with steel balls), H (bearing steel rings with ceramic balls) and X (heat-resistant high-speed steel rings with ceramic balls). Seals are coded V1V for non-contact rubber seals on both sides. Arrangements are DB, DF, DT and universal types; preload codes are EL, L, M and H; accuracy codes include P2, P4, P5 and the special P3W; the grease code MTR denotes ROBUSTGRD grease and MTS an NSK MTS grease, and X, K and L give the grease quantity as 15, 20 and 30 percent of the internal space.

Super precision bearings are normally supplied as sets matched to the chosen preload, so the arrangement and preload must be stated in the enquiry; the individual bearing is not a substitute. NSK also documents spacers, shaft and housing tolerances and lubrication in the same catalogue. For general industrial bearings see Electric Motors, Pumps and Turbines.

Where the 70BNR10H is used

The 70BNR10H belongs to a range designed for machine tool main spindles and high-speed motor spindles, where the bearing must hold the spindle nose precisely while running fast for long periods. Typical users are machining centres, high-speed milling heads, grinding spindles and other spindles where surface finish and dimensional accuracy depend directly on bearing behaviour. The combination of an angular contact design, ceramic balls and the NSKROBUST internal geometry is aimed at keeping heat generation low as speed rises, so the spindle remains thermally stable and the cutting position does not drift.

Spindle rebuild workshops also use this type when restoring a spindle to its original specification. In that case the safest approach is to match the designation from the removed bearings exactly, including the suffixes for cage, arrangement, preload, accuracy and grease, rather than substituting a similar size.

Selecting arrangement, preload and lubrication

Selection begins with the spindle design. A back-to-back (DB) arrangement gives higher moment stiffness and is common at the front of a spindle, while a face-to-face (DF) arrangement is more tolerant of misalignment. Tandem (DT) sets share axial load in one direction, and universal types allow the arrangement to be chosen at assembly. The preload class then balances stiffness against speed: a lighter preload favours speed and lower heat, while a heavier preload gives more rigidity for heavy cutting. The catalogue preload tables for this series should be consulted with the spindle designer before the order is fixed.

Lubrication has the same weight in the decision. Grease lubrication is simpler and is chosen where the grease speed limit is adequate, while oil-air or oil mist is used when the spindle runs closer to the oil limit. The grease codes in the numbering system let the bearing be ordered pre-greased with a stated grease type and quantity, which saves handling in the workshop.

Handling and installation practice

Super precision bearings need clean conditions. Open the packaging only at the assembly bench, keep matched sets together exactly as they were packed. Check shaft and housing fits against the tolerances in the NSK catalogue before assembly, and use controlled heating rather than force when mounting on the shaft. After assembly, a running-in procedure for grease-lubricated spindles helps distribute the grease and settle the temperature before full-speed operation.

Workshop conditions in Oman and the GCC

Machine shops in Oman often face high ambient temperatures and fine airborne dust, especially in industrial areas near open ground. Both affect spindle bearings: dust is a contamination risk during assembly, and heat reduces the margin on lubricant life. Store the bearings in their original packaging in a cool, dry room, assemble spindles in a clean area away from grinding and cutting, and make sure the machine is clean and in good order before the rebuilt spindle is returned to service.

Documents and quotation

Confirm bore, material (S, H or X), cage, seal, arrangement, preload, accuracy class, grease and the lubrication method (grease, oil-air or oil mist). The attached PDF is a page extract from the NSK Super Precision Bearings catalogue (Cat. No. E1254) with the numbering system and the BNR10 tables for 40 to 80 mm bores. Seven Star LLC is an independent supplier in Muscat; availability and lead time are confirmed per enquiry.