Super-Precision Double-Row Cylindrical Roller Bearing 85x130x34 mm, Tapered 1:12 Bore, Polyamide Cage, SP Precision Class

What this part is:
A double-row cylindrical roller bearing of the NN 30 series in super-precision execution: 85 mm bore, 130 mm outside diameter, 34 mm width. Two rows of rollers sit between a two-flange outer ring and a ribbed inner ring, giving very high radial load capacity and, more to the point, very high radial rigidity in a short axial section. It carries essentially no thrust and no misalignment. This is a machine-tool spindle bearing: it is the radial member of a spindle bearing arrangement and is normally paired with angular contact thrust bearings or a double-direction thrust bearing that locate the spindle axially.

Decoding the designation:
Read in SKF’s super-precision scheme.

NN 30 — double-row cylindrical roller bearing, NN 30 dimension series.17 — bore code: 17 × 5 = 85 mm bore.K — tapered bore, 1:12 taper. On this bearing the taper is not a convenience, it is the adjustment mechanism.TN9 — injection-moulded glass-fibre-reinforced polyamide 6,6 cage. Low mass, quiet, low friction, and tolerant of brief oil starvation, with a temperature ceiling well below a machined cage.SP — SKF super-precision tolerance class, covering both dimensional and running accuracy. This is a precision class, not a clearance class, and it is the reason the bearing exists as a distinct product from an ordinary NN 3017.The related /SPW33 variant adds an outer-ring lubrication groove and holes; this designation as listed does not carry W33.

Correcting the source data:
The previous copy stated the bearing was “meticulously crafted in Italy” and repeated the claim as a mark of quality. Nothing on this record substantiates a country of origin, and origin errors on this shelf are common, so the claim is removed and no origin is now published. The old text also omitted the two facts that actually decide the sale — that the bore is tapered and that SP is a precision class — and carried shipping and contact boilerplate, which has been deleted. The recorded UPC 7316572121085 begins 73165, SKF’s own EAN prefix, so the SKF attribution is independently corroborated.

What a tapered bore buys you, and what it costs:
In a spindle, radial internal clearance is not something you accept — it is something you set. Driving the inner ring up the 1:12 taper expands it and reduces clearance, which is how a spindle builder dials in a small negative clearance (a light preload) for maximum rigidity and minimum runout, or a small positive clearance where thermal growth is expected. The cost is that the bearing cannot go onto a plain cylindrical shaft. It needs a matching 1:12 tapered spindle seat, or an adapter sleeve with its lock nut and locking device. Drive-up must be measured, not judged: overdrive it and the rollers are preloaded hard, the spindle runs hot and the bearing fails quickly; underdrive it and you have thrown away the rigidity you paid for.

Component completeness:
The bearing only. No adapter sleeve, lock nut, lock washer, spacer or matched thrust bearing is included, and no photo has been confirmed to show one. A spindle rebuild will normally also need the axial-locating bearings and the correct spacer set — ask us, because if we hold matching super-precision angular contact bearings in the same bore they belong in the same shipment.

Published ratings and mounting data:
Bore d: 85 mm, tapered 1:12 · Outside diameter D: 130 mm · Width B: 34 mmBore tolerance: 0 to +0.020 mm · Outside diameter tolerance: −0.011 mm to 0 · Width tolerance: −0.20 mm to 0Chamfer, inner ring r3,4 (min): 0.6 mm · Chamfer, outer ring r1,2 (min): 1.1 mmPermissible axial displacement, maximum: 2 mmApproximate mass: 1.55 kgRings and rollers: chrome (through-hardened bearing) steel. Cage: glass-fibre-reinforced polyamide.Indicative performance figures published for this envelope by a distributor source: dynamic radial rating approximately 28,125 lbf (about 125 kN), static radial rating approximately 45,900 lbf (about 204 kN), maximum speed on the order of 7,000–8,000 r/min. Sanity check: the static figure exceeds the dynamic figure, as it should for a roller bearing. These are distributor-tier figures, not SKF-published values for the KTN9/SP designation, so treat them as provisional; skf.com is not directly readable by our tooling. The dedicated rating attributes are left blank rather than filled with unverified numbers.

Quantity and configuration:
Each unit is one complete bearing — outer ring, both roller rows, cage, inner ring — and the assembly is not separable. Stock on this line is recorded as 57. Super-precision spindle bearings are frequently stocked and sold as sets, and the recorded number may count pieces or packs, so we are publishing no piece-count guarantee: ask for a verified count before committing to a quantity, and we will physically count the shelf. Volume pricing is available.

Fitting notes:
Handle as a precision component: clean bench, lint-free cloths, no impact of any kind, and do not unwrap until the moment of fitting. Mount by measured drive-up on the taper, checking either residual radial clearance or axial advance against the spindle builder’s figures. Respect the polyamide cage’s temperature limit — do not induction-heat this bearing to conventional temperatures and keep it away from lubricants aggressive to nylon. Grease quantity in a spindle is small and deliberate; overfilling causes exactly the temperature rise the SP class is meant to avoid.

Interchange guidance:
Close SKF relatives are NN 3017 KTN9/SPW33 (adds the outer-ring lubrication groove), NN 3017 TN9/SP (straight bore — different mounting, not a drop-in) and the /VQ554 and /VS019 special-clearance variants. Other-brand equivalents in the same envelope include NSK NN3017TBKR and the RHP/NSK LNN-series machine-tool numbers, FAG NN3017-AS-K-M-SP and NTN NN3017K. Match the precision class as well as the number: an ordinary NN 3017 is not a substitute for an SP bearing in a spindle, and an SP bearing fitted with normal-class mounting practice will not deliver its accuracy.