Tag Archive for: slewing bearing replacement

When a machine stops because its slewing bearing has failed, the first obstacle is often not the repair itself but the missing paperwork. The nameplate has worn away, the original drawing was never handed over, or the machine maker no longer supports the model.

The good news is that a slewing bearing can be fully specified from careful measurements and a few clear photos. This guide walks you through the process step by step, and shows what to send to your supplier so the replacement fits the first time.

Before You Start: Preparation and What to Record

Take measurements only after the bearing has been safely removed and cleaned. Support the machine properly and release all loads before removal, and remove old grease and dirt so the markings and tooth surfaces are visible.

Before measuring, record the following:

• Machine information: make, model, serial number and year, if known.
• Application and working conditions: for example excavator, crane or turntable, plus load type, speed, temperature and environment.
• Installation orientation: which ring is fixed to the base, which ring carries the gear, and where the gear sits relative to the drive pinion.
• Photos: end faces, the side profile, the gear, the sealing area and any remaining markings.

Check every surface for stamped numbers or marks. Even a partial number on a ring face can help your supplier narrow down the type.

Step 1: Identify the Bearing Type

The structure of a slewing bearing determines its load capacity, so the type must be identified before any dimensions are matched. Look at the cross-section, the number of rolling-element rows and the overall height.

• Single row four-point contact ball slewing bearing: one row of balls, a relatively slim section and a compact design. A filling plug hole is often visible on one of the rings. See our four point contact ball slewing bearings.
• Double row ball slewing bearing: two rows of balls, a taller section and a higher load capacity than a single row. See our double row ball slewing bearings.
• Double row different diameter ball slewing bearing: two rows of balls of different sizes, usually for applications with large axial loads and overturning moments. See our double row different diameter ball slewing bearings.
• Three-row roller slewing bearing: three rows of rollers, a stepped ring section and the highest load capacity, common in heavy equipment. See our three-row roller slewing bearings.
• Cross roller slewing bearing: rollers arranged crosswise in a single raceway, with a compact, rigid section for applications that need high rotational accuracy. See our cross roller slewing bearings.
• Flanged slewing bearing: one ring has an integrated flange with mounting holes. See our flanged slewing bearings.

If you are unsure, take clear photos of the cross-section and the filling plug area, and send them to an engineer for confirmation. A wrong type is the most costly mistake in a replacement.

Step 2: Measure the Main Dimensions and Mounting Holes

Measure each dimension at several positions around the bearing and take the average. This reduces the effect of wear and deformation. Use a vernier caliper, a tape measure for large diameters and a thread gauge for threaded holes.

Dimension	How to measure	Common mistake
Outer diameter (OD)	Measure the outer ring body across several positions. If the bearing has an external gear, also measure the gear tip diameter separately.	Mixing up the ring body and the gear tip diameter.
Inner diameter (ID)	Measure the bore across several positions. For an internal gear, record the tooth tip diameter separately.	Measuring on a worn or deformed area.
Overall height	Measure from the bottom face to the top face at several points, and record each ring’s height.	Measuring at a point where the face is damaged or uneven.
Mounting hole PCD (pitch circle diameter)	Measure center to center across two opposite holes. For an odd number of holes, measure the center distance between adjacent holes (chord c) and calculate PCD = c ÷ sin(180° ÷ n), where n is the number of holes.	Measuring edge to edge instead of center to center.
Hole count and size	Count the holes on each ring. Record the diameter, and for threaded holes the thread size and depth. Note whether the holes are through or blind.	Assuming both rings use the same hole pattern, or mixing metric and imperial threads.

Record the inner ring and the outer ring separately, as their hole patterns and sizes are often different.

Step 3: Identify the Gear and Other Critical Details

If your bearing has a gear, it must match the drive pinion exactly. Identify the following:

• Gear position: external gear, internal gear or no gear, and which ring carries it.
• Number of teeth and tip diameter: count the teeth and measure the tip diameter on the least worn section.
• Module: for a standard gear, the module can be estimated as tip diameter ÷ (number of teeth + 2). Gears with profile shift or heavy wear will not follow this formula exactly, so confirm with a gear gauge or send photos for engineering review.
• Tooth width and gear hardening: record the tooth width, and note whether the teeth are induction hardened or untreated.
• Soft zone marking: the raceway hardening has a small gap, often marked on the ring face. Note its position relative to the filling plug, as it should not sit in the main load zone. For more detail, see Understanding Slewing Bearing Soft Zones.
• Seals, grease fittings and cage or spacers: note the seal type, the number and position of lubrication points and any special features.

Worn teeth give misleading measurements. Always measure on the least damaged teeth, and photograph the worn zone so engineers can account for it.

Replacement Inquiry Checklist: What to Send to Your Supplier

Incomplete information is the main reason a replacement does not fit. Send the following in one message:

1. Bearing type (or clear cross-section photos if unsure).
2. Outer diameter, inner diameter and overall height.
3. Mounting hole PCD, hole count, hole size or thread on both rings.
4. Gear data: position, tooth count, tip diameter, module estimate, tooth width and hardening.
5. Machine make and model, plus the application and working conditions.
6. Photos of the end faces, section, gear, seals and any remaining markings.
7. Quantity and required delivery time.

If measurements and photos disagree, tell your supplier. It is much easier to resolve a difference before production than after delivery.

Why Choose LDB Bearing for Slewing Bearing Replacement

Luoyang Longda Bearing Co., Ltd. (LDB Bearing) was established in 1999 in Luoyang, Henan, China’s bearing production base. Our registered trademark is LDB®, and we produce slewing bearings and gear rings from 150mm to 4000mm in diameter, in both standard and non-standard specifications.

• Quality system: our slewing bearings and slew drives hold ISO9001:2015 certification and German TÜV certification (2019), with process and quality control from raw material entry to finished product delivery.
• Global experience: LDB products have been exported to 73 countries and regions across Asia, America, Oceania and beyond.
• Replacement capability: we supply replacement slewing bearings for excavators and other heavy machinery, including equipment from brands such as Cat, Komatsu, Hyundai, Kubota, Hitachi, Kobelco, Volvo, Liebherr, JCB and John Deere.
• Complete product range: single row four-point contact ball, double row ball, double row different diameter ball, three-row roller, cross roller and flanged slewing bearings, as well as slew drives and spur gear drives.
• Support without drawings: send us your measurements, photos or the old bearing details, and our team will review your information and confirm the specification in your quotation.

Contact LDB today or email Tony@ldb-bearing.com to get a quote for your replacement slewing bearing.

Brand names are used only to indicate the equipment on which our replacement bearings are applied, and remain the property of their respective owners.

FAQ

Q1: Can you make a replacement slewing bearing from an old, damaged one with no markings?

Please send your measurements and photos. Our team will review them and confirm the specification in your quotation. Clear photos and accurate measurements make the process faster and more reliable.

Q2: What is the minimum information I need to send for a quotation?

A: At minimum, send the bearing type, outer diameter, inner diameter, height, mounting hole PCD and hole count, gear information if any, the machine make and model, and photos of the bearing. The more complete the information, the more accurate the quotation.

Q3: How do I know whether my bearing is a four-point contact ball or a double row ball type?

A: Count the rows of rolling elements and look at the section. A single row four-point contact ball bearing has one row of balls and a slimmer section, while a double row ball bearing has two rows and a taller section. If you are unsure, send cross-section photos for confirmation.

Q4: What is PCD and why does the mounting hole layout matter?

A: PCD (pitch circle diameter) is the diameter of the circle passing through the centers of the mounting holes. If the PCD, hole count or hole size is wrong, the replacement cannot be bolted to the machine, even if every other dimension matches.

Q5: Can LDB supply a replacement for a branded excavator or crane slewing bearing?

A: Yes. LDB supplies replacement slewing bearings for excavators and other heavy machinery from many brands. Please send the machine make, model and serial number along with your measurements so we can confirm the correct specification.

Q6: How long does it take to produce a replacement slewing bearing?

A: Lead time depends on the bearing type, size, and whether a drawing is available. Contact LDB with your measurements or photos, and our team will confirm the production schedule in your quotation.