Graphite Plugging & Grooving

Q: Are graphite-plugged bronze bushings self-lubricating?

A plain cast bronze bushing is not self-lubricating. Adding graphite plugs or graphite-filled grooves builds a dry lubricant into the bearing surface, so the bushing lubricates itself in service without oil or grease. Only sintered bronze (SAE 841, SAE 863) is self-lubricating as a base material.

Q: What is the difference between graphite plugging and graphite grooving?

Plugging fills a drilled hole pattern with solid graphite plugs; as the bearing wears, fresh graphite keeps transferring to the shaft. Grooving fills machined channels with graphite instead, exposing more graphite surface area for more immediate and continuous dry lubrication.

Q: Which bronze alloys work with graphite plugging?

C93200 (SAE 660) covers most general bearing applications. C95400 aluminum bronze handles higher loads and shock. C86300 manganese bronze is the choice for extreme loads at slow speeds, including graphite-plugged wear plates and guide plates.

Q: Can you add graphite to a standard catalog bushing?

Yes. We machine plug patterns or graphite grooves into our standard-size cast bronze bushings, or produce complete custom parts to your print with the graphite work included. Most standard items quote same day.

Dry lubrication machined into bronze bushings, bearings, and wear plates.

Cast bronze is not self-lubricating on its own. Embedding solid graphite in the bearing surface changes that. The part carries its own lubricant for the whole service life.

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Two Ways to Add Graphite

Graphite brings two properties to a bronze bearing: it lubricates without oil or grease, and it keeps working at temperatures where both break down. We machine it into the part in one of two configurations.

Graphite Plugging

Holes are drilled into the bearing surface in a specified pattern, then filled with solid graphite plugs under high pressure. As the bearing wears, fresh graphite keeps transferring to the shaft, so lubrication continues over the full service life. Common in construction equipment pivot bushings, furnace components, and processes where grease would burn off or contaminate the product.

Graphite-Filled Grooves

Channels are machined into the bearing surface and filled with graphite. Grooves expose more graphite surface area than plugs, which means more immediate and continuous dry lubrication and longer intervals between service points.

When to Spec Graphite Instead of Oil or Grease

Graphite earns its cost in a specific set of conditions. If your application checks one or more of these boxes, it is worth a look:

High load at low speed. Pivot points, oscillating joints, and slow-turning shafts operate in boundary lubrication, where an oil film cannot fully form. Embedded graphite handles metal-to-metal contact that would squeeze grease out.
High temperature. Standard greases and oils often break down between 200°F and 300°F. Graphite keeps lubricating well past that, which is why furnace and oven equipment runs on graphite-plugged bronze.
Re-lubrication is impractical. Elevated, sealed, submerged, or remote locations where nobody can reach a grease fitting on schedule.
Contamination-sensitive processes. Food, packaging, and finishing lines where migrating grease is a defect, not a maintenance item.

Rotating shafts with a working lubrication system or a regular greasing schedule are usually better served by oil and grease grooves.

Alloy Pairings

The graphite does the lubricating; the bronze carries the load. We match the base alloy to the demand:

C93200 (SAE 660) bearing bronze. The first choice for most plugged bushings. General purpose bearing service at moderate loads and speeds.
C95400 aluminum bronze. Steps up load capacity and shock resistance for heavier equipment.
C86300 manganese bronze. Extreme loads at slow speeds. Graphite-plugged C86300 wear plates and guide plates are a standard configuration in die and mold work.

Graphite Plugging & Grooving FAQs

Are graphite-plugged bronze bushings self-lubricating?

What is the difference between graphite plugging and graphite grooving?

When should I choose graphite over oil or grease grooves?

Choose graphite for high loads at low speeds, operating temperatures above roughly 300°F where grease and oil break down, and locations that are hard or impossible to re-lubricate. Rotating shafts with a working lubrication system or a regular greasing schedule are usually better served by oil and grease grooves.

Is graphite-plugged the same as graphite-impregnated?

The terms are often used interchangeably for bronze. Both describe solid graphite embedded in the bearing surface through drilled holes or machined grooves. If a spec sheet calls for graphite-impregnated bronze bushings, a graphite-plugged or graphite-grooved part machined to the same print typically satisfies it. Send the print and we will confirm.

Which bronze alloys work with graphite plugging?

Can you add graphite to a standard catalog bushing?

Send Your Drawing

Upload your print with the plug pattern or groove callouts, or describe the application and we will recommend the right approach. Works for standard-size bushings and complete custom parts alike.

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