Kubota KX61-3 Dipper Arm Repair – Worn Bucket Pin Bore Replaced

A worn bucket pin bore on a Kubota KX61-3 dipper arm can be repaired back to factory spec by replacing the worn boss with a new, case-hardened boss and hardened bushes. Simply Welding repaired a worn bucket pin bore on a Kubota KX61-3 mini digger dipper arm. The worn bore was found during a routine LOLER inspection in Coventry. The arm was stripped and brought back to our workshop in the heart of the Black Country, where we repaired it back to factory spec. It was then refitted, tested and given a fresh LOLER certificate, all in a two-day turnaround.

Job Description

We repaired a worn and damaged bucket pin bore on a Kubota KX61-3 dipper arm.

Material Used

A high-strength alloy steel, case hardened to give a tough, fatigue-resistant boss with excellent wear properties that still keeps its strength.

Removing the Worn Boss

We removed the old boss from the dipper arm by plasma arc gouging. The dipper arm was then cleaned up and prepared for welding, with all the welding contact points chamfered to allow a full penetration welded joint.

Machining the New Boss

We faced off both ends of the steel slug, broke the edges (chamfered the sharp corners) and brought it to its finished length. The centre hole was then drilled and bored to take the new hardened bushes. This dimension was critical, as the bushes needed to be an interference fit, and we left a landing ledge inside the bore for the bushes to butt up against.

Fitting the New Bushes

The new hardened bushes were pressed (jacked) into the bore using a hydraulic press, where the interference fit held them firmly in place.

Lining Up the New Boss

We lined up the dipper arm and new boss to exact factory dimensions (we have specs for most of the Kubota mini and midi digger range). Once everything was lined up, we tack-welded the boss to the dipper arm and re-checked the alignment before fully welding.

Fully Welding

The dipper arm and new boss were preheated to a set temperature and fully welded to a specific welding procedure using dual-shield welding wire. The welded assembly was then wrapped in welding blankets and left to cool slowly over several hours, so the weld area did not change structure, become brittle and crack at a later date.

Final Prep

We applied three coats of etch primer and 3–4 coats of Kubota orange topcoat, then refitted the arm, tested it and delivered it back to the customer.

Result

The dipper arm went back to work at factory spec with a fresh LOLER certificate, two days after the worn bore was found.

Frequently Asked Questions

Can a worn bucket pin bore on a mini digger be repaired?

Yes. The worn boss is gouged out and replaced with a new case-hardened boss fitted with hardened bushes, then lined up to exact factory dimensions and fully welded.

What happens if a worn bore is found on a LOLER inspection?

A worn pin or bore found on a LOLER thorough examination needs to be repaired before the machine can be signed off. We can inspect, repair and re-certify in-house, so the machine is back at work with a fresh LOLER certificate quickly. This one was turned around in two days.

Why use hardened bushes in the new boss?

Hardened bushes give the bore a tough, wear-resistant surface for the pin to run in.

Do you have factory dimensions for Kubota diggers?

Yes. We have specs for most of the Kubota mini and midi digger range, so new bosses can be lined up to exact factory dimensions.

Why chamfer the dipper arm before welding in the new boss?

All the welding contact points are chamfered to allow a full penetration welded joint, so the new boss is welded through the full thickness of the steel rather than just on the surface.

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Worn pins or bores found on your LOLER inspection? We inspect, repair and re-certify. Call 07747 682451 or send us some photos via WhatsApp.