HK Series Drawn Cup Needle Roller Bearings

The open-ended drawn cup: a thin stamped outer ring whose ends are both open, the needle complement retained by the cup itself, and no inner ring at all — the shaft is the inner raceway. The designation has only two fields, and neither of them is a bore: in HK1210 the 12 is Fw, the needle complement diameter the shaft has to be ground to, and the 10 is C, the cup width. The outside diameter is not in the designation at all, which is why HK1210 is 16 mm across while HK1212 is 18 mm: an outside diameter comes from the ISO 3245 table for its diameter series, and the same pair of digits can belong to either. The series is pressed into a housing rather than mounted on a shaft shoulder, so the housing bore is the fit that matters.

Two fields, and neither of them is a bore. HK1210 is HK, then 12, then 10. The 12 is Fw — the diameter of the needle complement, and therefore the diameter the shaft has to be ground to — and the 10 is C, the width of the cup. Both are already in millimetres; neither is a code, and neither is multiplied by five. Nor is there a dimension series in the designation: what looks like one is the leading pair of the two size fields, which is why the same four digits can turn up under two different outside diameters.

The outside diameter is not in the number, and that is the point of the type. HK1210 is 16 mm across; HK1212 is 18 mm, on the same Fw and the same leading digits. The first is diameter series 1D and the second 2D, and the designation does not say which. Everywhere else in this library a designation fixes all of its boundary dimensions — here the outside diameter is the one figure that has to be read from the ISO 3245 table, for the diameter series the design calls for. HK1212 and BK1212 are the only 2D sizes this library carries.

HK and BK are one table with two ends. ISO 3245 heads a single boundary table with both forms — "with open ends or one closed end" — so a size made in both has one row of Fw, D and C and two designations. The cup is the difference: open at both ends in HK, formed into a base at one end in BK, where that base is what a shaft end can butt against. This library holds 37 sizes in both forms, 25 in HK alone and 1 in BK alone, and the uneven counts come from the sourcing rule rather than from the market: a size is printed only where two independent catalogues agree on all three figures.

No chamfer column, and no clearance row — for two different reasons. ISO 3245 does give a chamfer minimum alongside its boundary dimensions, but the catalogue tables consulted for this type print Fw, D and C only, so the cell has no second source and is not printed. The missing clearance row is not a sourcing problem at all: ISO 5753-1 leaves drawn cup needle roller bearings out of its scope in as many words, so there is no table in that standard for this page to reproduce.

Sizes outside the standard's table. Four of the sizes here are not rows of the ISO 3245 table — HK0306 and BK0306 sit below the table's smallest Fw, and HK1312 and BK1312 take an Fw the table skips — and a further fifteen take an outside diameter the table gives but a cup width it does not list for that Fw. All of them are printed, because each has two independent catalogues agreeing on Fw, D and C, and each page says which case it is in. The alternative would be to drop sizes that are bought and sold every day because a standard did not happen to tabulate them.

How far the series runs. HK0306 at the bottom and HK6012 at the top: an Fw of 3 to 60 mm, an outside diameter of 6.5 to 68 mm and a cup width of 6 to 38 mm. The bottom of that range is below the 10 mm floor the rest of this library's bore-code ladder starts at, which is possible precisely because Fw is not a bore code.

This series runs from a 3 mm to a 60 mm shaft. The sub-library as a whole reaches 300 mm of bore, and the widest single bearing in it is a 6360, 620 mm across, in the 6300 series. It shares its outside-diameter ladder with the complete bearings of the same dimension series.

Fw = needle complement diameter, D = outside diameter, C = width. All of them are ISO 3245 standard values and are the same for every manufacturer. C is the width of the cup. The outer ring of this type is a thin stamped shell rather than a machined ring, so there is one width to state and no inner ring to state one for: Fw is the diameter the shaft has to be ground to, D the outside diameter of that shell, and of the three only Fw and C appear in the designation. The last column is derived: radial section = (D − Fw) / 2, the wall thickness you are working with when you size the housing. No load rating and no limiting speed appears here — see the bearings index for why.

Outside diameter × overall size in millimetres, for the 5 smallest bores in this database. The full charts, one per type, are on the bearings index. Reading a row is what a machine designer does when the shaft is already fixed: the bore does not change, the housing bore does. Across the type boundary the last number changes meaning — it is a width above and a height below — so compare within a type, then decide whether the job wants a ball bearing, a tapered roller or a thrust bearing at all. The 6 series whose type has no bore are not rows here: they are indexed by the shaft they run on, and their chart is above.