JCB 3CX Dipper Arm Repair – Replacing Worn Pivot Bosses and Oval Bores

Simply Welding repaired a JCB 3CX backhoe dipper arm with two badly worn pivot bosses. Worn or oval pivot bosses on a JCB 3CX dipper arm can be cut out and replaced with new, case-hardened bosses, saving the cost of a new dipper arm. The pivot bosses on the dipper arm of this JCB 3CX compact backhoe had worn oval. We cut out the worn bosses, turned new ones in our workshop and welded them back into place, and the backhoe went back to work maintaining roads and footpaths around the West Midlands.

Job Description

We repaired a pair of worn bores / bosses on the dipper arm of a JCB 3CX compact backhoe.

Cause of the Damage

This machine had spent most of its life working on road planing and resurfacing of roads, footpaths and car parks, much of it with a hydraulic breaker fitted. This caused excessive wear to two bores on the dipper arm.

Removal and Inspection

We removed the dipper arm from the excavator and took it back to our workshop. It was cleaned and checked for any other defects, and we took initial measurements to make sure the fit-up would be correct after the repair.

Removing the Worn Bosses

The bosses weren't welded to the flange faces. They passed through the arm flange and were welded on both sides. We cut off the exposed part of each boss on the outside of the dipper arm, then opened up the bore until we could see the fusion zone of the original weld. This kept the original dimensions and let us remove the rest of the boss.

Machining New Bosses

We turned new bosses from high-quality steel, weld-preparing them at the same time, and sent them away for case hardening to give the repair a long life.

Preparing for Welding

The area to be welded was thoroughly cleaned, all paint was ground off, and the joints were bevelled.

Fit-Up

Working from our original measurements, we inserted the new bosses and tack-welded them in place. We then offered the dipper arm up to the boom on the excavator to confirm everything fitted before fully welding.

Welding and Refitting

Once the fit-up had been confirmed by us and by the customer, the bosses were fully welded with dual-shield welding wire, cleaned up and refitted to the JCB 3CX.

Result

The machine was back, running and working perfectly, maintaining the road and footpath network around the West Midlands.

Frequently Asked Questions

What causes worn bosses on a JCB 3CX dipper arm?

Heavy, repetitive work wears the pivot bores oval over time. On this JCB 3CX, years of road planing and resurfacing work, much of it with a hydraulic breaker fitted, caused excessive wear to two bores on the dipper arm.

Can worn dipper arm bosses be replaced instead of buying a new arm?

Yes. The worn bosses can be cut out back to the original weld, new bosses turned and weld-prepared, then fitted to the original measurements and fully welded, at a fraction of the cost of a new dipper arm.

Why are the new bosses case hardened?

Case hardening gives the new bosses a hard, wear-resistant surface, so the repair lasts much longer than the original bosses did.

Can you repair worn pivot bosses on other makes of excavator?

Yes, where the component and its condition are suitable. Similar boss and bore repairs are possible on other makes and models of excavators, backhoe loaders and heavy plant. Each component is assessed individually to decide the right repair method.

Do you offer workshop and mobile repairs?

Yes. We carry out workshop-based engineering and welding repairs as well as mobile welding on site. This job was done in our workshop, which is the best place for a repair needing machining and precise fit-up; the right location depends on the component and the work needed.

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Watch the repair: the worn bosses cut out of the JCB 3CX dipper arm, the bores opened up on the milling machine, then the new bosses pre-heated and fully welded into place.