Numbers wear off. Plates corrode, labels peel, and a part that came out of a machine in a hurry often goes back in with nothing left to read. The instinct is to photograph it and ask a supplier to guess. A better answer is to measure it: five dimensions taken with a caliper and a thread gauge will identify most hydraulic and undercarriage parts more reliably than a photograph, because a photograph cannot tell a 0.5 mm difference in seal height. This is the measurement protocol Guangzhou Shenyue Machinery Technology Co., Ltd. uses when a customer sends an unmarked component.
Measure the part, not the machine
Model and serial narrow the field, but they never pick the part. Within one model there are several builds, and within one assembly there are variants that share a housing and differ internally. Dimensions are the only evidence that survives a repaint. Take them with the part clean and dry, at room temperature, and write them down to 0.1 mm — a phone note is fine, a guess is not.
| Part type | What to measure | Where people go wrong |
|---|---|---|
| Lip seal | Bore OD, shaft ID, height, lip material | Measuring the old seal after it has been pressed out of shape |
| O-ring | Inside diameter and cross-section | Quoting OD and CS, which double-counts the section |
| Bearing | Bore, OD, width, roller type | Assuming a metric series from an inch-looking number |
| Bolt or stud | Thread diameter, pitch, length, grade | Pitch measured with a ruler instead of a gauge |
| Hose end | Thread form, seat angle, hex size | Confusing BSP and JIC, which look similar and seal differently |
| Shaft or coupling | Spline count, major diameter, involute or straight | Counting teeth on the worn side and losing one |
Seals: four dimensions and one material
A seal is defined by bore, shaft, height and lip material. Measure the bore in the housing, not the old seal, and measure the shaft where the lip actually runs — a groove worn by the old lip reads smaller than the nominal shaft and will leak with a new seal of the correct size. Material matters as much as size on a Kobelco: nitrile covers most hydraulic and gear oil duties, while high-temperature and certain synthetic fluids call for a fluoroelastomer. A seal that is dimensionally perfect and materially wrong fails within weeks, and it fails in a way that looks like a bad installation. Section sizes for these parts are published by the seal makers themselves, for example nok.co.jp.
Bearings: bore, OD, width — and the three-number habit
Bearing PNUP309ET / 2441U474S123 / 2437U534S123 shows how the numbering works in practice. One physical bearing, recorded against the K3V180, K7V125 and K7V140 pump platforms, carrying the bearing maker's designation plus two machine-side references. If you can read any one of them, the part is identified; if you cannot read any, the bore, OD and width will still narrow it to a series. Record the roller type as well — cylindrical, tapered and needle bearings of the same envelope are not interchangeable, whatever the dimension table suggests. Bearing envelope standards are published by the makers, for example skf.com.
Threads, splines and fittings
Thread pitch needs a gauge, not arithmetic. A 1.5 mm and a 16 threads-per-inch fastener look alike on a caliper and will not mate. On hose ends, identify the thread form and the seat angle together: a JIC 37-degree flare and a BSP parallel seat are both common on Kobelco machines depending on market and build, and mixing them produces a joint that tightens, holds briefly, and then weeps. Splines need a count plus the major diameter, and an involute profile cannot be matched by a straight-sided shaft that happens to have the same tooth count.
Photo protocol that works. Six images: the part on a plain background with a ruler alongside, the worn face, any remaining stamping, the mating bore, the machine serial plate, and the surrounding assembly. Add the five measurements in text. Guangzhou Shenyue Machinery Technology Co., Ltd. checks dimensions against stock before quoting through the contact page, and confirms whether the part is genuine, OEM or aftermarket — the three are priced separately and are not interchangeable in a high-pressure circuit.
When measurement is not enough
Some parts cannot be resolved by dimension alone: matched sets, preloaded bearings, and anything with a running change inside the same envelope. In those cases the fallback is the assembly. Quoting the parent number — the pump, the motor or the cylinder — is more expensive but it is answerable, and it beats a third attempt at a seal that keeps weeping. Send the measurements, send the photos, and check them against our part-number search before a number is assumed. Guangzhou Shenyue Machinery Technology Co., Ltd. prices both routes, so the choice becomes a comparison rather than a gamble.
Frequently Asked Questions
How do I identify a Kobelco part with no number on it?
Measure it. Record bore, shaft or OD, width or height, thread pitch and spline count, then send those figures with photographs of the part and the machine serial. Guangzhou Shenyue Machinery Technology Co., Ltd. matches dimensions against stock records before quoting, which is more reliable than identifying from a photograph.
Can I match a hydraulic seal by its outside diameter only?
No. A lip seal is defined by bore, shaft, height and lip material, and two seals with the same OD can differ in all three of the others. Measure the housing bore and the running surface of the shaft, not the deformed old seal, and confirm the material for the oil and temperature in use.
Why does one bearing have three part numbers?
Because the bearing maker's designation and the machine-side references coexist. PNUP309ET / 2441U474S123 / 2437U534S123 is one bearing recorded against the K3V180, K7V125 and K7V140 pump platforms. Any one of the three numbers identifies the part, so a partial reading is often still enough.
What if the part cannot be identified at all?
Quote the parent assembly instead. Matched sets and parts with internal running changes cannot always be resolved by dimension, and a pump, motor or cylinder assembly number is answerable where a single seal is not. Guangzhou Shenyue Machinery Technology Co., Ltd. will price both routes so the decision is a comparison, not a gamble.