H-304 adapter sleeve: complete specifications & mounting data
The H-304 is an adapter sleeve sized 20 x 32 x 28 mm (tapered bore x sleeve OD x width) for a plain 17 mm metric shaft with M 20x1 thread supplied with the KM 4 lock nut at 40 g per ISO 2982-1. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 20 mm |
| Outer diameter D | 32 mm |
| Width B | 28 mm |
| Fits shaft diameter | 17 mm |
| Sleeve thread G | M 20x1 |
| Included lock nut | KM 4 |
| Included locking device | MB 4 |
| Material | Carbon_Steel |
| Mass | 40 g |
| Manufacturer designation | H 304 |
| Standard | ISO 2982-1 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 23.1 adapter sleeves for metric shafts |
| Last verified | 2026-09-30 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 23.1 adapter sleeves for metric shafts) · extracted 2026-09-30
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 23.1 adapter sleeves for metric shafts); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & H3-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.26 in |
| Width B | 1.102 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 6 mm |
| Smallest bore in H3-series | 20 mm |
| Largest outer diameter in H3-series | 145 mm |
| Width range across H3-series | 28–77 mm |
| Bore position in H3-series (smallest first) | 1 of 18 |
| Bore above smallest H3-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| H | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; standard interchange — confirm clearance class and precision with the supplier. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the H-304 model number is decoded
mass 40 g is 2.0 g per mm of bore; the sleeve with its KM 4 nut and MB 4 washer forms the complete 28 mm-wide mounting assembly this sleeve mounts a bearing with a 20 mm tapered bore onto a plain 17 mm shaft; the 32 mm outside diameter and 28 mm width define the tapered seat the bearing is driven onto mounting and dismounting stay purely mechanical: the KM 4 nut drives the taper home, and backing the nut off releases the 20 mm seat without oil-injection tooling the 3 mm difference between the 17 mm shaft and the 20 mm nominal seat diameter is bridged by taper contraction as the slit sleeve closes during drive-up, rather than by machining the shaft the M 20x1 thread spans about 28.0 nut turns across the 28 mm width; each indexed turn is a measurable drive-up step when setting the bearing clearance on the 20 mm seat at 17 mm shaft diameter this is one of the smallest metric sleeves in the catalogue, typical for light self-aligning ball bearings on instrument and small-motor shafts with the H execution the KM 4 lock nut and MB 4 washer are delivered together — the washer is a single-use element that should be renewed whenever the 20 mm seat is remounted within the medium-section H 3 range, the default seat for 13..K and 22..K self-aligning ball bearings and 222..K spherical roller bearings this is the 17 mm shaft step; neighbouring steps keep the same hardware concept while the taper seat grows to 20x32 mm here the delivery includes the KM 4 lock nut and the MB 4 locking washer; drive-up is measured by clearance reduction as the bearing climbs the taper typical applications include agricultural machinery axle and PTO shafts, quarry conveyor head and tail drums and paper machine roll and cylinder journals adapter sleeves earn their place wherever a tapered-bore bearing must sit at any axial position on a plain shaft — here a 20 mm bore bearing on a 17 mm shaft in paper machine roll and cylinder journals the sleeve lets the designer use a plain, unstepped shaft and still locate the bearing positively; only one shoulder is needed, opposite the KM 4 nut kit identity for this seat: sleeve H 304 for a 17 mm shaft, 20x32x28 mm taper, M 20x1 thread, KM 4 nut with MB 4 washer, catalogue mass 40 g
Typical equipment & failure modes
Common applications
- mining crusher and screen exciter shafts
- agricultural machinery axle and PTO shafts
- electric motor and generator shafts
- rolling mill and steel plant roll seats
Known failure patterns
- the shaft must be within h9 tolerance and free of scoring; an oversize or rough shaft stops the slit sleeve closing down and leaves the grip to the thread alone
- a plain KM nut used without its MB washer has no anti-rotation feature and will unthread under vibration
- mounting without a fixed abutment lets the bearing walk axially; the sleeve needs a shaft shoulder opposite the lock nut
- over-driving the taper eliminates bearing internal clearance entirely; clearance reduction must be measured with feeler gauges, not estimated from nut torque
- greasing the tapered seat or shaft destroys the dry friction the joint relies on; a lubricated taper can let the whole sleeve spin under load
Selection pitfalls — read before you substitute
- the shaft must be within h9 tolerance and free of scoring; an oversize or rough shaft stops the slit sleeve closing down and leaves the grip to the thread alone
- mounting without a fixed abutment lets the bearing walk axially; the sleeve needs a shaft shoulder opposite the lock nut
- bending more than one washer tab to force alignment work-hardens both tabs; choose the single closest slot only
Frequently asked questions
What shaft size does the H-304 adapter sleeve fit?
H-304 (H 304) mounts on a plain metric shaft of 17 mm and carries a bearing with a 20 mm tapered (K) bore; sleeve OD is 32 mm and width 28 mm.
What does the H 304 designation mean?
H identifies a standard metric adapter sleeve in the H3 series; the size code encodes the 20 mm tapered bore (bore code × 5 mm).
What is supplied with the H-304?
The kit contains the KM 4 lock nut and MB 4 locking washer. Mounting uses a hook spanner, controlling clearance reduction as the 20 mm bearing climbs the taper.
How much does the H-304 adapter sleeve weigh?
The listed mass is 40 g for the sleeve assembly at 20x32x28 mm — about 1.4 g per millimetre of sleeve width.
How is the H-304 mounted on the shaft?
Lubricate the M 20x1 thread lightly, screw the KM 4 home, then tighten to the catalogue axial displacement while measuring clearance reduction on the 20 mm bearing, and finally bend the MB 4 washer tab.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 23.1 adapter sleeves for metric shafts on 2026-09-30. Read our editorial & correction policy.