Komatsu Part BUSHING 21N-72-12170

—

Product Overview

The 21N-72-12170 BUSHING is a genuine Komatsu OEM replacement bushing from the 21N prefix series. Bushings are the silent workers at every pivot joint in your machine — they take the friction, the surface wear, and the environmental abuse so the more expensive pin and housing bore don't have to. When a bushing wears out, replacing it restores the factory-spec clearance in the joint at a fraction of the cost of replacing the pin and housing.

Part Number: 21N-72-12170 Part Name: BUSHING Part Type: OEM Komatsu Replacement Bushing Availability: In stock

—

The Wear Mechanism

Bushings wear through a combination of abrasive and adhesive wear. Dirt works past the seals and embeds in the relatively soft bushing surface, acting like a fine grinding compound. Each oscillation of the pin within the bushing removes a microscopic amount of material. Over thousands of cycles, the bore enlarges, the wall thins, and the clearance grows.

What makes bushing wear particularly destructive is that once the clearance opens up beyond a certain point, the loading changes from gradual surface contact to impact loading. The pin hammers against the bushing with each direction change, accelerating the wear rate. This is why catching bushing wear early is important — the cost escalates quickly once impact damage begins.

—

When to Replace

• Excessive clearance between the bushing bore and the pin — detectable by rocking the joint and feeling for play
• The bushing bore is visibly oval-shaped or elongated rather than round
• Surface cracks, galling, scoring, or embedded debris visible on the bore surface
• Grease purging past the bushing to the outside — the clearance has grown beyond the seal's ability to retain it
• The pin shows a visible wear ridge — if the pin is worn, the bushing is almost certainly worse

—

Installation

1. Confirm 21N-72-12170 in your Komatsu catalog
2. Remove the old bushing — use a press or driver with the correct pilot diameter
3. Clean the housing bore — all old bushing fragments must be removed
4. Inspect the mating pin — replace it if there is any visible wear step or surface damage
5. Press the new bushing to the specified depth — flush is typical unless noted otherwise
6. Apply assembly grease to the bushing bore before inserting the pin
7. Cycle the joint and pump fresh grease until clean grease appears at the seals

—

Request a Quote

Need the Komatsu 21N-72-12170 BUSHING? Contact us through the form or by phone, email, or WhatsApp. We respond within one business day.