The 63/28X (28×72×18 mm / 1.102×2.835×0.709 in) is a non-standard deep groove ball bearing manufactured to a customer-specific dimension outside standard ISO sizing. "63/28X" is the informal designation this size is known by among customers — it is not a catalog or ISO part number, but a real, recurring size we manufacture for OEM replacement.

This size does not appear in any standard bearing catalog. The nearest true standard-series bearing, the 6306 (30×72×19 mm), does not fit — the bore is 2 mm too large and the width is 1 mm off. That gap is exactly why equipment using this OEM cavity ends up with a forced, ill-fitting replacement if the correct non-standard size isn't sourced.

Manufactured to match original OEM tolerances, load balance, sealing performance, and internal clearance, the 63/28X is built as a drop-in replacement — no shaft grinding, housing machining, or shimming required.

Note: This is a different size from our 63/28 2RS C3 (28×68×18 mm) — both fall under the broader 63/28 non-standard family, but they are not interchangeable. Always confirm which outer diameter your equipment requires before ordering.

Technical Specifications

Available Configurations

• 63/28X Open Type — no seal, for high-speed or easy-maintenance applications

• 63/28X ZZ — double metal shield

• 63/28X 2RS — double rubber seal, dustproof and waterproof (most common configuration)

• Optional C3 / C4 internal clearance — for high-temperature and high-vibration operating conditions

Why the Outer Diameter Matters

Bearings in the 63/28 non-standard family exist in more than one outer diameter, depending on the original OEM design. Using the wrong variant — even within the same "non-standard" family — causes the same failure pattern as forcing a fully standard bearing into a non-standard cavity:

• Undersized OD creates a loose fit in the housing, uneven contact pressure, and raceway tilt

• Oversized OD forced into a smaller housing causes excessive preload, overheating, and premature fatigue

• Either mismatch leads to abnormal gear meshing, mechanical resonance, and repeated emergency shutdowns

The 63/28X is manufactured specifically for OEM cavities that require the 72 mm outer diameter. Always confirm the exact OD against your equipment before ordering — a 4 mm difference is enough to cause a failed fit.

Typical Applications

• Legacy Import Equipment: Discontinued OEM machinery originally built with this exact cavity size

• Industrial Motors & Gearboxes: Equipment requiring the oversized OD variant for correct housing fit

• Agricultural Machinery: Tractors, harvesters, and transmissions operating in dusty, high-vibration conditions

• Export-Grade Mechanical Units: Custom-built equipment manufactured to non-ISO specifications

Cross-Reference & Interchangeability

The 28×72×18 mm dimension is not covered by any standard ISO or ABMA catalog size. It corresponds to a customer-specific OEM cavity, most commonly found on legacy or imported equipment where the original manufacturer used a non-standard outer diameter.

If you have a sample, drawing, worn part, or the equipment's model number, our engineering team can measure and confirm the exact specification — including whether your equipment needs the 68 mm or 72 mm outer diameter variant — before you order.

Customization Options

• Material: GCr15 chrome steel (standard), stainless steel options available

• Seal Type: Open, ZZ, or 2RS

• Clearance: Standard, C3, or C4

• Precision: P0 standard, P6 custom

• Lubrication: Custom grease options for high-temperature or low-noise requirements

Frequently Asked Questions (FAQs)

Q: Is "63/28X" an official bearing part number?

A: No. It's the informal designation this size is commonly known by among customers. The actual specification is 28×72×18 mm, and we manufacture it to match your OEM requirements exactly.

Q: How is this different from the 63/28 2RS C3?

A: They belong to the same non-standard 63/28 family but have different outer diameters — 72 mm for the 63/28X versus 68 mm for the 63/28 2RS C3. They are not interchangeable. Confirm your equipment's exact OD before ordering.

Q: Can a standard 6306 bearing replace this size?

A: No. The 6306 measures 30×72×19 mm — the bore is 2 mm too large and the width is 1 mm off, which will not fit the original housing or shaft correctly.

Q: What is the lead time for custom orders?

A: Standard samples are available in 7–10 days; mass production lead time is 15–25 days, depending on order quantity and customization requirements.

Q: Do you offer stainless steel versions?

A: Yes, stainless steel material options are available for corrosion-resistant applications — let us know your operating environment when ordering.

Call to Action

If you're not sure whether your equipment needs the 68 mm or 72 mm outer diameter variant, don't guess — send us the dimensions, a photo, or a physical sample. Our engineers will confirm the exact specification and recommend the correct replacement within 24 hours.