Manufactured to ISO 355 / DIN ISO 355 / GB/T 297, 30300 Series Tapered Roller Bearings are tapered roller bearings supplied by Bushing Bearings. Every designation in the series is listed with its boundary dimensions; the interactive half-section drawing redraws itself for whichever size you select.
What Are 30300 Series Tapered Roller Bearings?
30300 Series Tapered Roller Bearings are tapered roller bearings defined by ISO 355 / DIN ISO 355 / GB/T 297. They are selected by bearing designation and the dimensional characteristics shown below. Material, cage and sealing are specified separately from the designation and are covered further down this page.
Materials & Cage
Cone, cup and rollers are case-hardened 20CrMnTi / SAE 8620 as standard — this family is normally carburized rather than through-hardened, because the raceways see line contact under heavy shock. Cages are pressed steel. Stainless and high-temperature variants exist but are the exception; state the operating temperature if it exceeds 120 degrees C, because the standard heat stabilization limit governs.
Typical Applications
Wheel hubs, pinion and axle shafts, gearboxes and machine tool spindles, carrying heavy combined radial and axial load in opposed pairs. Read the full application guide for 30300 Series Tapered Roller Bearings →
Pricing
30300 Series Tapered Roller Bearings are supplied to order. Pricing starts from approximately US$3.50 per piece for standard bore sizes as a matched cone-and-cup set in case-hardened steel; final pricing depends on size, material, finish and order quantity (MOQ applies). Submit your exact configuration with the quote form above.
Specifying the 30300 Series Tapered Roller Bearings
The sizes specified most often from this range are 50 mm bore, 55 mm bore, 60 mm bore and 65 mm bore. Each has its own page, so a drawing can be checked against one bore without reading the whole table above.
Where the environment decides the specification rather than the load, the material pages are the ones to read: GCr15 Bearing Steel, Case-Hardened 20CrMnTi and Pressed Steel Cage. Each states what the grade survives, and what choosing it costs in load capacity or temperature range.
The dimensions above are fixed by GB/T 297 and DIN 720 — that is what makes one maker's bearing interchangeable with another's, and it is worth checking which standard a quotation is written to. For the machines and duties this type is actually specified for, see where 30300 series tapered roller bearings are fitted.
Manufactured in our own plant
This bearing is forged, hardened, ground, superfinished and clearance-set in-house. The stages below are where its tolerance class, its internal clearance and its noise grade are actually decided.
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01 Forging & turning
GCr15 bar and tube is cut, heated and forged into ring blanks, then turned to leave a uniform grinding allowance. Forging rather than machining from solid keeps the grain flow following the raceway, which is the surface that eventually fails.
Blank dimensions and grinding stock checked at set-up and per shift.
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02 Heat treatment
Through-hardening brings GCr15 / 100Cr6 to 58–64 HRC; carburizing case-hardens 20CrMnTi where the section is heavy or the load is shock. Rings are then stabilized so they hold size in service rather than growing in the housing.
Core and surface hardness per lot; retained austenite and dimensional stability to the ordered temperature class.
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03 Raceway grinding
Faces, bore, outer diameter and raceway are ground in sequence on separate machines. This is where the tolerance class is created: P0, P6, P5 or P4 is a grinding outcome, not a sorting outcome.
Bore and outer diameter deviation, raceway roundness and face runout measured to ISO 492 on every setup.
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04 Honing & superfinishing
The ground raceway is honed to remove the grinding lay and bring surface roughness down to a fraction of a micrometre. Raceway finish is what decides whether a lubricant film forms, and therefore what decides bearing life far more than the load rating alone.
Surface roughness Ra and waviness measured per lot.